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2018-06-15mm/swapfile.c: fix swap_count comment about nonexistent SWAP_HAS_CONTDaniel Jordan
Commit 570a335b8e22 ("swap_info: swap count continuations") introduces COUNT_CONTINUED but refers to it incorrectly as SWAP_HAS_CONT in a comment in swap_count. Fix it. Link: http://lkml.kernel.org/r/20180612175919.30413-1-daniel.m.jordan@oracle.com Fixes: 570a335b8e22 ("swap_info: swap count continuations") Signed-off-by: Daniel Jordan <daniel.m.jordan@oracle.com> Reviewed-by: Andrew Morton <akpm@linux-foundation.org> Cc: "Huang, Ying" <ying.huang@intel.com> Cc: Hugh Dickins <hughd@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2018-06-12treewide: kvzalloc() -> kvcalloc()Kees Cook
The kvzalloc() function has a 2-factor argument form, kvcalloc(). This patch replaces cases of: kvzalloc(a * b, gfp) with: kvcalloc(a * b, gfp) as well as handling cases of: kvzalloc(a * b * c, gfp) with: kvzalloc(array3_size(a, b, c), gfp) as it's slightly less ugly than: kvcalloc(array_size(a, b), c, gfp) This does, however, attempt to ignore constant size factors like: kvzalloc(4 * 1024, gfp) though any constants defined via macros get caught up in the conversion. Any factors with a sizeof() of "unsigned char", "char", and "u8" were dropped, since they're redundant. The Coccinelle script used for this was: // Fix redundant parens around sizeof(). @@ type TYPE; expression THING, E; @@ ( kvzalloc( - (sizeof(TYPE)) * E + sizeof(TYPE) * E , ...) | kvzalloc( - (sizeof(THING)) * E + sizeof(THING) * E , ...) ) // Drop single-byte sizes and redundant parens. @@ expression COUNT; typedef u8; typedef __u8; @@ ( kvzalloc( - sizeof(u8) * (COUNT) + COUNT , ...) | kvzalloc( - sizeof(__u8) * (COUNT) + COUNT , ...) | kvzalloc( - sizeof(char) * (COUNT) + COUNT , ...) | kvzalloc( - sizeof(unsigned char) * (COUNT) + COUNT , ...) | kvzalloc( - sizeof(u8) * COUNT + COUNT , ...) | kvzalloc( - sizeof(__u8) * COUNT + COUNT , ...) | kvzalloc( - sizeof(char) * COUNT + COUNT , ...) | kvzalloc( - sizeof(unsigned char) * COUNT + COUNT , ...) ) // 2-factor product with sizeof(type/expression) and identifier or constant. @@ type TYPE; expression THING; identifier COUNT_ID; constant COUNT_CONST; @@ ( - kvzalloc + kvcalloc ( - sizeof(TYPE) * (COUNT_ID) + COUNT_ID, sizeof(TYPE) , ...) | - kvzalloc + kvcalloc ( - sizeof(TYPE) * COUNT_ID + COUNT_ID, sizeof(TYPE) , ...) | - kvzalloc + kvcalloc ( - sizeof(TYPE) * (COUNT_CONST) + COUNT_CONST, sizeof(TYPE) , ...) | - kvzalloc + kvcalloc ( - sizeof(TYPE) * COUNT_CONST + COUNT_CONST, sizeof(TYPE) , ...) | - kvzalloc + kvcalloc ( - sizeof(THING) * (COUNT_ID) + COUNT_ID, sizeof(THING) , ...) | - kvzalloc + kvcalloc ( - sizeof(THING) * COUNT_ID + COUNT_ID, sizeof(THING) , ...) | - kvzalloc + kvcalloc ( - sizeof(THING) * (COUNT_CONST) + COUNT_CONST, sizeof(THING) , ...) | - kvzalloc + kvcalloc ( - sizeof(THING) * COUNT_CONST + COUNT_CONST, sizeof(THING) , ...) ) // 2-factor product, only identifiers. @@ identifier SIZE, COUNT; @@ - kvzalloc + kvcalloc ( - SIZE * COUNT + COUNT, SIZE , ...) // 3-factor product with 1 sizeof(type) or sizeof(expression), with // redundant parens removed. @@ expression THING; identifier STRIDE, COUNT; type TYPE; @@ ( kvzalloc( - sizeof(TYPE) * (COUNT) * (STRIDE) + array3_size(COUNT, STRIDE, sizeof(TYPE)) , ...) | kvzalloc( - sizeof(TYPE) * (COUNT) * STRIDE + array3_size(COUNT, STRIDE, sizeof(TYPE)) , ...) | kvzalloc( - sizeof(TYPE) * COUNT * (STRIDE) + array3_size(COUNT, STRIDE, sizeof(TYPE)) , ...) | kvzalloc( - sizeof(TYPE) * COUNT * STRIDE + array3_size(COUNT, STRIDE, sizeof(TYPE)) , ...) | kvzalloc( - sizeof(THING) * (COUNT) * (STRIDE) + array3_size(COUNT, STRIDE, sizeof(THING)) , ...) | kvzalloc( - sizeof(THING) * (COUNT) * STRIDE + array3_size(COUNT, STRIDE, sizeof(THING)) , ...) | kvzalloc( - sizeof(THING) * COUNT * (STRIDE) + array3_size(COUNT, STRIDE, sizeof(THING)) , ...) | kvzalloc( - sizeof(THING) * COUNT * STRIDE + array3_size(COUNT, STRIDE, sizeof(THING)) , ...) ) // 3-factor product with 2 sizeof(variable), with redundant parens removed. @@ expression THING1, THING2; identifier COUNT; type TYPE1, TYPE2; @@ ( kvzalloc( - sizeof(TYPE1) * sizeof(TYPE2) * COUNT + array3_size(COUNT, sizeof(TYPE1), sizeof(TYPE2)) , ...) | kvzalloc( - sizeof(TYPE1) * sizeof(THING2) * (COUNT) + array3_size(COUNT, sizeof(TYPE1), sizeof(TYPE2)) , ...) | kvzalloc( - sizeof(THING1) * sizeof(THING2) * COUNT + array3_size(COUNT, sizeof(THING1), sizeof(THING2)) , ...) | kvzalloc( - sizeof(THING1) * sizeof(THING2) * (COUNT) + array3_size(COUNT, sizeof(THING1), sizeof(THING2)) , ...) | kvzalloc( - sizeof(TYPE1) * sizeof(THING2) * COUNT + array3_size(COUNT, sizeof(TYPE1), sizeof(THING2)) , ...) | kvzalloc( - sizeof(TYPE1) * sizeof(THING2) * (COUNT) + array3_size(COUNT, sizeof(TYPE1), sizeof(THING2)) , ...) ) // 3-factor product, only identifiers, with redundant parens removed. @@ identifier STRIDE, SIZE, COUNT; @@ ( kvzalloc( - (COUNT) * STRIDE * SIZE + array3_size(COUNT, STRIDE, SIZE) , ...) | kvzalloc( - COUNT * (STRIDE) * SIZE + array3_size(COUNT, STRIDE, SIZE) , ...) | kvzalloc( - COUNT * STRIDE * (SIZE) + array3_size(COUNT, STRIDE, SIZE) , ...) | kvzalloc( - (COUNT) * (STRIDE) * SIZE + array3_size(COUNT, STRIDE, SIZE) , ...) | kvzalloc( - COUNT * (STRIDE) * (SIZE) + array3_size(COUNT, STRIDE, SIZE) , ...) | kvzalloc( - (COUNT) * STRIDE * (SIZE) + array3_size(COUNT, STRIDE, SIZE) , ...) | kvzalloc( - (COUNT) * (STRIDE) * (SIZE) + array3_size(COUNT, STRIDE, SIZE) , ...) | kvzalloc( - COUNT * STRIDE * SIZE + array3_size(COUNT, STRIDE, SIZE) , ...) ) // Any remaining multi-factor products, first at least 3-factor products, // when they're not all constants... @@ expression E1, E2, E3; constant C1, C2, C3; @@ ( kvzalloc(C1 * C2 * C3, ...) | kvzalloc( - (E1) * E2 * E3 + array3_size(E1, E2, E3) , ...) | kvzalloc( - (E1) * (E2) * E3 + array3_size(E1, E2, E3) , ...) | kvzalloc( - (E1) * (E2) * (E3) + array3_size(E1, E2, E3) , ...) | kvzalloc( - E1 * E2 * E3 + array3_size(E1, E2, E3) , ...) ) // And then all remaining 2 factors products when they're not all constants, // keeping sizeof() as the second factor argument. @@ expression THING, E1, E2; type TYPE; constant C1, C2, C3; @@ ( kvzalloc(sizeof(THING) * C2, ...) | kvzalloc(sizeof(TYPE) * C2, ...) | kvzalloc(C1 * C2 * C3, ...) | kvzalloc(C1 * C2, ...) | - kvzalloc + kvcalloc ( - sizeof(TYPE) * (E2) + E2, sizeof(TYPE) , ...) | - kvzalloc + kvcalloc ( - sizeof(TYPE) * E2 + E2, sizeof(TYPE) , ...) | - kvzalloc + kvcalloc ( - sizeof(THING) * (E2) + E2, sizeof(THING) , ...) | - kvzalloc + kvcalloc ( - sizeof(THING) * E2 + E2, sizeof(THING) , ...) | - kvzalloc + kvcalloc ( - (E1) * E2 + E1, E2 , ...) | - kvzalloc + kvcalloc ( - (E1) * (E2) + E1, E2 , ...) | - kvzalloc + kvcalloc ( - E1 * E2 + E1, E2 , ...) ) Signed-off-by: Kees Cook <keescook@chromium.org>
2018-05-25mm: fix nr_rotate_swap leak in swapon() error caseOmar Sandoval
If swapon() fails after incrementing nr_rotate_swap, we don't decrement it and thus effectively leak it. Make sure we decrement it if we incremented it. Link: http://lkml.kernel.org/r/b6fe6b879f17fa68eee6cbd876f459f6e5e33495.1526491581.git.osandov@fb.com Fixes: 81a0298bdfab ("mm, swap: don't use VMA based swap readahead if HDD is used as swap") Signed-off-by: Omar Sandoval <osandov@fb.com> Reviewed-by: Rik van Riel <riel@surriel.com> Reviewed-by: "Huang, Ying" <ying.huang@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2018-04-11mm/swapfile.c: make pointer swap_avail_heads staticColin Ian King
The pointer swap_avail_heads is local to the source and does not need to be in global scope, so make it static. Cleans up sparse warning: mm/swapfile.c:88:19: warning: symbol 'swap_avail_heads' was not declared. Should it be static? Link: http://lkml.kernel.org/r/20180206215836.12366-1-colin.king@canonical.com Signed-off-by: Colin Ian King <colin.king@canonical.com> Reviewed-by: Andrew Morton <akpm@linux-foundation.org> Acked-by: "Huang, Ying" <ying.huang@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2018-04-11swap: divide-by-zero when zero length swap file on ssdTom Abraham
Calling swapon() on a zero length swap file on SSD can lead to a divide-by-zero. Although creating such files isn't possible with mkswap and they woud be considered invalid, it would be better for the swapon code to be more robust and handle this condition gracefully (return -EINVAL). Especially since the fix is small and straightforward. To help with wear leveling on SSD, the swapon syscall calculates a random position in the swap file using modulo p->highest_bit, which is set to maxpages - 1 in read_swap_header. If the swap file is zero length, read_swap_header sets maxpages=1 and last_page=0, resulting in p->highest_bit=0 and we divide-by-zero when we modulo p->highest_bit in swapon syscall. This can be prevented by having read_swap_header return zero if last_page is zero. Link: http://lkml.kernel.org/r/5AC747C1020000A7001FA82C@prv-mh.provo.novell.com Signed-off-by: Thomas Abraham <tabraham@suse.com> Reported-by: <Mark.Landis@Teradata.com> Reviewed-by: Andrew Morton <akpm@linux-foundation.org> Cc: Randy Dunlap <rdunlap@infradead.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2018-02-11vfs: do bulk POLL* -> EPOLL* replacementLinus Torvalds
This is the mindless scripted replacement of kernel use of POLL* variables as described by Al, done by this script: for V in IN OUT PRI ERR RDNORM RDBAND WRNORM WRBAND HUP RDHUP NVAL MSG; do L=`git grep -l -w POLL$V | grep -v '^t' | grep -v /um/ | grep -v '^sa' | grep -v '/poll.h$'|grep -v '^D'` for f in $L; do sed -i "-es/^\([^\"]*\)\(\<POLL$V\>\)/\\1E\\2/" $f; done done with de-mangling cleanups yet to come. NOTE! On almost all architectures, the EPOLL* constants have the same values as the POLL* constants do. But they keyword here is "almost". For various bad reasons they aren't the same, and epoll() doesn't actually work quite correctly in some cases due to this on Sparc et al. The next patch from Al will sort out the final differences, and we should be all done. Scripted-by: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-11-27ipc, kernel, mm: annotate ->poll() instancesAl Viro
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2017-11-15mm: swap: SWP_SYNCHRONOUS_IO: skip swapcache only if swapped page has no ↵Minchan Kim
other reference When SWP_SYNCHRONOUS_IO swapped-in pages are shared by several processes, it can cause unnecessary memory wastage by skipping swap cache. Because, with swapin fault by read, they could share a page if the page were in swap cache. Thus, it avoids allocating same content new pages. This patch makes the swapcache skipping work only if the swap pte is non-sharable. [akpm@linux-foundation.org: coding-style fixes] Link: http://lkml.kernel.org/r/1507620825-5537-1-git-send-email-minchan@kernel.org Signed-off-by: Minchan Kim <minchan@kernel.org> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Ross Zwisler <ross.zwisler@linux.intel.com> Cc: Hugh Dickins <hughd@google.com> Cc: Christoph Hellwig <hch@lst.de> Cc: Ilya Dryomov <idryomov@gmail.com> Cc: Jens Axboe <axboe@kernel.dk> Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Cc: Huang Ying <ying.huang@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-11-15mm, swap: skip swapcache for swapin of synchronous deviceMinchan Kim
With fast swap storage, the platforms want to use swap more aggressively and swap-in is crucial to application latency. The rw_page() based synchronous devices like zram, pmem and btt are such fast storage. When I profile swapin performance with zram lz4 decompress test, S/W overhead is more than 70%. Maybe, it would be bigger in nvdimm. This patch aims to reduce swap-in latency by skipping swapcache if the swap device is synchronous device like rw_page based device. It enhances 45% my swapin test(5G sequential swapin, no readahead, from 2.41sec to 1.64sec). Link: http://lkml.kernel.org/r/1505886205-9671-5-git-send-email-minchan@kernel.org Signed-off-by: Minchan Kim <minchan@kernel.org> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Ross Zwisler <ross.zwisler@linux.intel.com> Cc: Hugh Dickins <hughd@google.com> Cc: Christoph Hellwig <hch@lst.de> Cc: Ilya Dryomov <idryomov@gmail.com> Cc: Jens Axboe <axboe@kernel.dk> Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Cc: Huang Ying <ying.huang@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-11-15mm, swap: introduce SWP_SYNCHRONOUS_IOMinchan Kim
If rw-page based fast storage is used for swap devices, we need to detect it to enhance swap IO operations. This patch is preparation for optimizing of swap-in operation with next patch. Link: http://lkml.kernel.org/r/1505886205-9671-4-git-send-email-minchan@kernel.org Signed-off-by: Minchan Kim <minchan@kernel.org> Cc: Hugh Dickins <hughd@google.com> Cc: Christoph Hellwig <hch@lst.de> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Ilya Dryomov <idryomov@gmail.com> Cc: Jens Axboe <axboe@kernel.dk> Cc: Ross Zwisler <ross.zwisler@linux.intel.com> Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Cc: Huang Ying <ying.huang@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-11-03mm, swap: fix race between swap count continuation operationsHuang Ying
One page may store a set of entries of the sis->swap_map (swap_info_struct->swap_map) in multiple swap clusters. If some of the entries has sis->swap_map[offset] > SWAP_MAP_MAX, multiple pages will be used to store the set of entries of the sis->swap_map. And the pages are linked with page->lru. This is called swap count continuation. To access the pages which store the set of entries of the sis->swap_map simultaneously, previously, sis->lock is used. But to improve the scalability of __swap_duplicate(), swap cluster lock may be used in swap_count_continued() now. This may race with add_swap_count_continuation() which operates on a nearby swap cluster, in which the sis->swap_map entries are stored in the same page. The race can cause wrong swap count in practice, thus cause unfreeable swap entries or software lockup, etc. To fix the race, a new spin lock called cont_lock is added to struct swap_info_struct to protect the swap count continuation page list. This is a lock at the swap device level, so the scalability isn't very well. But it is still much better than the original sis->lock, because it is only acquired/released when swap count continuation is used. Which is considered rare in practice. If it turns out that the scalability becomes an issue for some workloads, we can split the lock into some more fine grained locks. Link: http://lkml.kernel.org/r/20171017081320.28133-1-ying.huang@intel.com Fixes: 235b62176712 ("mm/swap: add cluster lock") Signed-off-by: "Huang, Ying" <ying.huang@intel.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Shaohua Li <shli@kernel.org> Cc: Tim Chen <tim.c.chen@intel.com> Cc: Michal Hocko <mhocko@suse.com> Cc: Aaron Lu <aaron.lu@intel.com> Cc: Dave Hansen <dave.hansen@intel.com> Cc: Andi Kleen <ak@linux.intel.com> Cc: Minchan Kim <minchan@kernel.org> Cc: Hugh Dickins <hughd@google.com> Cc: <stable@vger.kernel.org> [4.11+] Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-09-08mm/swapfile.c: fix swapon frontswap_map memory leak on errorDavid Rientjes
Free frontswap_map if an error is encountered before enable_swap_info(). Signed-off-by: David Rientjes <rientjes@google.com> Reviewed-by: "Huang, Ying" <ying.huang@intel.com> Cc: Darrick J. Wong <darrick.wong@oracle.com> Cc: Hugh Dickins <hughd@google.com> Cc: <stable@vger.kernel.org> [4.12+] Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-09-08mm: kvfree the swap cluster info if the swap file is unsatisfactoryDarrick J. Wong
If initializing a small swap file fails because the swap file has a problem (holes, etc.) then we need to free the cluster info as part of cleanup. Unfortunately a previous patch changed the code to use kvzalloc but did not change all the vfree calls to use kvfree. Found by running generic/357 from xfstests. Link: http://lkml.kernel.org/r/20170831233515.GR3775@magnolia Fixes: 54f180d3c181 ("mm, swap: use kvzalloc to allocate some swap data structures") Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com> Reviewed-by: "Huang, Ying" <ying.huang@intel.com> Acked-by: David Rientjes <rientjes@google.com> Cc: Hugh Dickins <hughd@google.com> Cc: <stable@vger.kernel.org> [4.12+] Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-09-06swap: choose swap device according to numa nodeAaron Lu
If the system has more than one swap device and swap device has the node information, we can make use of this information to decide which swap device to use in get_swap_pages() to get better performance. The current code uses a priority based list, swap_avail_list, to decide which swap device to use and if multiple swap devices share the same priority, they are used round robin. This patch changes the previous single global swap_avail_list into a per-numa-node list, i.e. for each numa node, it sees its own priority based list of available swap devices. Swap device's priority can be promoted on its matching node's swap_avail_list. The current swap device's priority is set as: user can set a >=0 value, or the system will pick one starting from -1 then downwards. The priority value in the swap_avail_list is the negated value of the swap device's due to plist being sorted from low to high. The new policy doesn't change the semantics for priority >=0 cases, the previous starting from -1 then downwards now becomes starting from -2 then downwards and -1 is reserved as the promoted value. Take 4-node EX machine as an example, suppose 4 swap devices are available, each sit on a different node: swapA on node 0 swapB on node 1 swapC on node 2 swapD on node 3 After they are all swapped on in the sequence of ABCD. Current behaviour: their priorities will be: swapA: -1 swapB: -2 swapC: -3 swapD: -4 And their position in the global swap_avail_list will be: swapA -> swapB -> swapC -> swapD prio:1 prio:2 prio:3 prio:4 New behaviour: their priorities will be(note that -1 is skipped): swapA: -2 swapB: -3 swapC: -4 swapD: -5 And their positions in the 4 swap_avail_lists[nid] will be: swap_avail_lists[0]: /* node 0's available swap device list */ swapA -> swapB -> swapC -> swapD prio:1 prio:3 prio:4 prio:5 swap_avali_lists[1]: /* node 1's available swap device list */ swapB -> swapA -> swapC -> swapD prio:1 prio:2 prio:4 prio:5 swap_avail_lists[2]: /* node 2's available swap device list */ swapC -> swapA -> swapB -> swapD prio:1 prio:2 prio:3 prio:5 swap_avail_lists[3]: /* node 3's available swap device list */ swapD -> swapA -> swapB -> swapC prio:1 prio:2 prio:3 prio:4 To see the effect of the patch, a test that starts N process, each mmap a region of anonymous memory and then continually write to it at random position to trigger both swap in and out is used. On a 2 node Skylake EP machine with 64GiB memory, two 170GB SSD drives are used as swap devices with each attached to a different node, the result is: runtime=30m/processes=32/total test size=128G/each process mmap region=4G kernel throughput vanilla 13306 auto-binding 15169 +14% runtime=30m/processes=64/total test size=128G/each process mmap region=2G kernel throughput vanilla 11885 auto-binding 14879 +25% [aaron.lu@intel.com: v2] Link: http://lkml.kernel.org/r/20170814053130.GD2369@aaronlu.sh.intel.com Link: http://lkml.kernel.org/r/20170816024439.GA10925@aaronlu.sh.intel.com [akpm@linux-foundation.org: use kmalloc_array()] Link: http://lkml.kernel.org/r/20170814053130.GD2369@aaronlu.sh.intel.com Link: http://lkml.kernel.org/r/20170816024439.GA10925@aaronlu.sh.intel.com Signed-off-by: Aaron Lu <aaron.lu@intel.com> Cc: "Chen, Tim C" <tim.c.chen@intel.com> Cc: Huang Ying <ying.huang@intel.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Michal Hocko <mhocko@suse.com> Cc: Minchan Kim <minchan@kernel.org> Cc: Hugh Dickins <hughd@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-09-06mm, swap: don't use VMA based swap readahead if HDD is used as swapHuang Ying
VMA based swap readahead will readahead the virtual pages that is continuous in the virtual address space. While the original swap readahead will readahead the swap slots that is continuous in the swap device. Although VMA based swap readahead is more correct for the swap slots to be readahead, it will trigger more small random readings, which may cause the performance of HDD (hard disk) to degrade heavily, and may finally exceed the benefit. To avoid the issue, in this patch, if the HDD is used as swap, the VMA based swap readahead will be disabled, and the original swap readahead will be used instead. Link: http://lkml.kernel.org/r/20170807054038.1843-6-ying.huang@intel.com Signed-off-by: "Huang, Ying" <ying.huang@intel.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Minchan Kim <minchan@kernel.org> Cc: Rik van Riel <riel@redhat.com> Cc: Shaohua Li <shli@kernel.org> Cc: Hugh Dickins <hughd@google.com> Cc: Fengguang Wu <fengguang.wu@intel.com> Cc: Tim Chen <tim.c.chen@intel.com> Cc: Dave Hansen <dave.hansen@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-09-06mm, THP, swap: support splitting THP for THP swap outHuang Ying
After adding swapping out support for THP (Transparent Huge Page), it is possible that a THP in swap cache (partly swapped out) need to be split. To split such a THP, the swap cluster backing the THP need to be split too, that is, the CLUSTER_FLAG_HUGE flag need to be cleared for the swap cluster. The patch implemented this. And because the THP swap writing needs the THP keeps as huge page during writing. The PageWriteback flag is checked before splitting. Link: http://lkml.kernel.org/r/20170724051840.2309-8-ying.huang@intel.com Signed-off-by: "Huang, Ying" <ying.huang@intel.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Minchan Kim <minchan@kernel.org> Cc: Hugh Dickins <hughd@google.com> Cc: Shaohua Li <shli@kernel.org> Cc: Rik van Riel <riel@redhat.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Jens Axboe <axboe@kernel.dk> Cc: Michal Hocko <mhocko@kernel.org> Cc: Ross Zwisler <ross.zwisler@intel.com> [for brd.c, zram_drv.c, pmem.c] Cc: Vishal L Verma <vishal.l.verma@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-09-06mm, THP, swap: don't allocate huge cluster for file backed swap deviceHuang Ying
It's hard to write a whole transparent huge page (THP) to a file backed swap device during swapping out and the file backed swap device isn't very popular. So the huge cluster allocation for the file backed swap device is disabled. Link: http://lkml.kernel.org/r/20170724051840.2309-5-ying.huang@intel.com Signed-off-by: "Huang, Ying" <ying.huang@intel.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Minchan Kim <minchan@kernel.org> Cc: Hugh Dickins <hughd@google.com> Cc: Shaohua Li <shli@kernel.org> Cc: Rik van Riel <riel@redhat.com> Cc: "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Jens Axboe <axboe@kernel.dk> Cc: Michal Hocko <mhocko@kernel.org> Cc: Ross Zwisler <ross.zwisler@intel.com> [for brd.c, zram_drv.c, pmem.c] Cc: Vishal L Verma <vishal.l.verma@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-09-06mm, THP, swap: make reuse_swap_page() works for THP swapped outHuang Ying
After supporting to delay THP (Transparent Huge Page) splitting after swapped out, it is possible that some page table mappings of the THP are turned into swap entries. So reuse_swap_page() need to check the swap count in addition to the map count as before. This patch done that. In the huge PMD write protect fault handler, in addition to the page map count, the swap count need to be checked too, so the page lock need to be acquired too when calling reuse_swap_page() in addition to the page table lock. [ying.huang@intel.com: silence a compiler warning] Link: http://lkml.kernel.org/r/87bmnzizjy.fsf@yhuang-dev.intel.com Link: http://lkml.kernel.org/r/20170724051840.2309-4-ying.huang@intel.com Signed-off-by: "Huang, Ying" <ying.huang@intel.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Minchan Kim <minchan@kernel.org> Cc: Hugh Dickins <hughd@google.com> Cc: Shaohua Li <shli@kernel.org> Cc: Rik van Riel <riel@redhat.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Jens Axboe <axboe@kernel.dk> Cc: Michal Hocko <mhocko@kernel.org> Cc: Ross Zwisler <ross.zwisler@intel.com> [for brd.c, zram_drv.c, pmem.c] Cc: Vishal L Verma <vishal.l.verma@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-09-06mm, THP, swap: support to reclaim swap space for THP swapped outHuang Ying
The normal swap slot reclaiming can be done when the swap count reaches SWAP_HAS_CACHE. But for the swap slot which is backing a THP, all swap slots backing one THP must be reclaimed together, because the swap slot may be used again when the THP is swapped out again later. So the swap slots backing one THP can be reclaimed together when the swap count for all swap slots for the THP reached SWAP_HAS_CACHE. In the patch, the functions to check whether the swap count for all swap slots backing one THP reached SWAP_HAS_CACHE are implemented and used when checking whether a swap slot can be reclaimed. To make it easier to determine whether a swap slot is backing a THP, a new swap cluster flag named CLUSTER_FLAG_HUGE is added to mark a swap cluster which is backing a THP (Transparent Huge Page). Because THP swap in as a whole isn't supported now. After deleting the THP from the swap cache (for example, swapping out finished), the CLUSTER_FLAG_HUGE flag will be cleared. So that, the normal pages inside THP can be swapped in individually. [ying.huang@intel.com: fix swap_page_trans_huge_swapped on HDD] Link: http://lkml.kernel.org/r/874ltsm0bi.fsf@yhuang-dev.intel.com Link: http://lkml.kernel.org/r/20170724051840.2309-3-ying.huang@intel.com Signed-off-by: "Huang, Ying" <ying.huang@intel.com> Acked-by: Rik van Riel <riel@redhat.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Minchan Kim <minchan@kernel.org> Cc: Hugh Dickins <hughd@google.com> Cc: Shaohua Li <shli@kernel.org> Cc: "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Jens Axboe <axboe@kernel.dk> Cc: Michal Hocko <mhocko@kernel.org> Cc: Ross Zwisler <ross.zwisler@intel.com> [for brd.c, zram_drv.c, pmem.c] Cc: Vishal L Verma <vishal.l.verma@intel.com> Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-09-06mm, THP, swap: support to clear swap cache flag for THP swapped outHuang Ying
Patch series "mm, THP, swap: Delay splitting THP after swapped out", v3. This is the second step of THP (Transparent Huge Page) swap optimization. In the first step, the splitting huge page is delayed from almost the first step of swapping out to after allocating the swap space for the THP and adding the THP into the swap cache. In the second step, the splitting is delayed further to after the swapping out finished. The plan is to delay splitting THP step by step, finally avoid splitting THP for the THP swapping out and swap out/in the THP as a whole. In the patchset, more operations for the anonymous THP reclaiming, such as TLB flushing, writing the THP to the swap device, removing the THP from the swap cache are batched. So that the performance of anonymous THP swapping out are improved. During the development, the following scenarios/code paths have been checked, - swap out/in - swap off - write protect page fault - madvise_free - process exit - split huge page With the patchset, the swap out throughput improves 42% (from about 5.81GB/s to about 8.25GB/s) in the vm-scalability swap-w-seq test case with 16 processes. At the same time, the IPI (reflect TLB flushing) reduced about 78.9%. The test is done on a Xeon E5 v3 system. The swap device used is a RAM simulated PMEM (persistent memory) device. To test the sequential swapping out, the test case creates 8 processes, which sequentially allocate and write to the anonymous pages until the RAM and part of the swap device is used up. Below is the part of the cover letter for the first step patchset of THP swap optimization which applies to all steps. ========================= Recently, the performance of the storage devices improved so fast that we cannot saturate the disk bandwidth with single logical CPU when do page swap out even on a high-end server machine. Because the performance of the storage device improved faster than that of single logical CPU. And it seems that the trend will not change in the near future. On the other hand, the THP becomes more and more popular because of increased memory size. So it becomes necessary to optimize THP swap performance. The advantages of the THP swap support include: - Batch the swap operations for the THP to reduce TLB flushing and lock acquiring/releasing, including allocating/freeing the swap space, adding/deleting to/from the swap cache, and writing/reading the swap space, etc. This will help improve the performance of the THP swap. - The THP swap space read/write will be 2M sequential IO. It is particularly helpful for the swap read, which are usually 4k random IO. This will improve the performance of the THP swap too. - It will help the memory fragmentation, especially when the THP is heavily used by the applications. The 2M continuous pages will be free up after THP swapping out. - It will improve the THP utilization on the system with the swap turned on. Because the speed for khugepaged to collapse the normal pages into the THP is quite slow. After the THP is split during the swapping out, it will take quite long time for the normal pages to collapse back into the THP after being swapped in. The high THP utilization helps the efficiency of the page based memory management too. There are some concerns regarding THP swap in, mainly because possible enlarged read/write IO size (for swap in/out) may put more overhead on the storage device. To deal with that, the THP swap in should be turned on only when necessary. For example, it can be selected via "always/never/madvise" logic, to be turned on globally, turned off globally, or turned on only for VMA with MADV_HUGEPAGE, etc. This patch (of 12): Previously, swapcache_free_cluster() is used only in the error path of shrink_page_list() to free the swap cluster just allocated if the THP (Transparent Huge Page) is failed to be split. In this patch, it is enhanced to clear the swap cache flag (SWAP_HAS_CACHE) for the swap cluster that holds the contents of THP swapped out. This will be used in delaying splitting THP after swapping out support. Because there is no THP swapping in as a whole support yet, after clearing the swap cache flag, the swap cluster backing the THP swapped out will be split. So that the swap slots in the swap cluster can be swapped in as normal pages later. Link: http://lkml.kernel.org/r/20170724051840.2309-2-ying.huang@intel.com Signed-off-by: "Huang, Ying" <ying.huang@intel.com> Acked-by: Rik van Riel <riel@redhat.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Minchan Kim <minchan@kernel.org> Cc: Hugh Dickins <hughd@google.com> Cc: Shaohua Li <shli@kernel.org> Cc: "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Jens Axboe <axboe@kernel.dk> Cc: Michal Hocko <mhocko@kernel.org> Cc: Ross Zwisler <ross.zwisler@intel.com> [for brd.c, zram_drv.c, pmem.c] Cc: Vishal L Verma <vishal.l.verma@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-07-10swap: add block io poll in swapin pathShaohua Li
For fast flash disk, async IO could introduce overhead because of context switch. block-mq now supports IO poll, which improves performance and latency a lot. swapin is a good place to use this technique, because the task is waiting for the swapin page to continue execution. In my virtual machine, directly read 4k data from a NVMe with iopoll is about 60% better than that without poll. With iopoll support in swapin patch, my microbenchmark (a task does random memory write) is about 10%~25% faster. CPU utilization increases a lot though, 2x and even 3x CPU utilization. This will depend on disk speed. While iopoll in swapin isn't intended for all usage cases, it's a win for latency sensistive workloads with high speed swap disk. block layer has knob to control poll in runtime. If poll isn't enabled in block layer, there should be no noticeable change in swapin. I got a chance to run the same test in a NVMe with DRAM as the media. In simple fio IO test, blkpoll boosts 50% performance in single thread test and ~20% in 8 threads test. So this is the base line. In above swap test, blkpoll boosts ~27% performance in single thread test. blkpoll uses 2x CPU time though. If we enable hybid polling, the performance gain has very slight drop but CPU time is only 50% worse than that without blkpoll. Also we can adjust parameter of hybid poll, with it, the CPU time penality is reduced further. In 8 threads test, blkpoll doesn't help though. The performance is similar to that without blkpoll, but cpu utilization is similar too. There is lock contention in swap path. The cpu time spending on blkpoll isn't high. So overall, blkpoll swapin isn't worse than that without it. The swapin readahead might read several pages in in the same time and form a big IO request. Since the IO will take longer time, it doesn't make sense to do poll, so the patch only does iopoll for single page swapin. [akpm@linux-foundation.org: coding-style fixes] Link: http://lkml.kernel.org/r/070c3c3e40b711e7b1390002c991e86a-b5408f0@7511894063d3764ff01ea8111f5a004d7dd700ed078797c204a24e620ddb965c Signed-off-by: Shaohua Li <shli@fb.com> Cc: Tim Chen <tim.c.chen@intel.com> Cc: Huang Ying <ying.huang@intel.com> Cc: Jens Axboe <axboe@fb.com> Cc: Hugh Dickins <hughd@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-07-06mm/swapfile.c: sort swap entries before freeHuang Ying
To reduce the lock contention of swap_info_struct->lock when freeing swap entry. The freed swap entries will be collected in a per-CPU buffer firstly, and be really freed later in batch. During the batch freeing, if the consecutive swap entries in the per-CPU buffer belongs to same swap device, the swap_info_struct->lock needs to be acquired/released only once, so that the lock contention could be reduced greatly. But if there are multiple swap devices, it is possible that the lock may be unnecessarily released/acquired because the swap entries belong to the same swap device are non-consecutive in the per-CPU buffer. To solve the issue, the per-CPU buffer is sorted according to the swap device before freeing the swap entries. With the patch, the memory (some swapped out) free time reduced 11.6% (from 2.65s to 2.35s) in the vm-scalability swap-w-rand test case with 16 processes. The test is done on a Xeon E5 v3 system. The swap device used is a RAM simulated PMEM (persistent memory) device. To test swapping, the test case creates 16 processes, which allocate and write to the anonymous pages until the RAM and part of the swap device is used up, finally the memory (some swapped out) is freed before exit. [akpm@linux-foundation.org: tweak comment] Link: http://lkml.kernel.org/r/20170525005916.25249-1-ying.huang@intel.com Signed-off-by: Huang Ying <ying.huang@intel.com> Acked-by: Tim Chen <tim.c.chen@intel.com> Cc: Hugh Dickins <hughd@google.com> Cc: Shaohua Li <shli@kernel.org> Cc: Minchan Kim <minchan@kernel.org> Cc: Rik van Riel <riel@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-07-06mm, THP, swap: unify swap slot free functions to put_swap_pageMinchan Kim
Now, get_swap_page takes struct page and allocates swap space according to page size(ie, normal or THP) so it would be more cleaner to introduce put_swap_page which is a counter function of get_swap_page. Then, it calls right swap slot free function depending on page's size. [ying.huang@intel.com: minor cleanup and fix] Link: http://lkml.kernel.org/r/20170515112522.32457-3-ying.huang@intel.com Signed-off-by: Minchan Kim <minchan@kernel.org> Signed-off-by: "Huang, Ying" <ying.huang@intel.com> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Ebru Akagunduz <ebru.akagunduz@gmail.com> Cc: Hugh Dickins <hughd@google.com> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Michal Hocko <mhocko@kernel.org> Cc: Rik van Riel <riel@redhat.com> Cc: Shaohua Li <shli@kernel.org> Cc: Tejun Heo <tj@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-07-06mm, THP, swap: delay splitting THP during swap outHuang Ying
Patch series "THP swap: Delay splitting THP during swapping out", v11. This patchset is to optimize the performance of Transparent Huge Page (THP) swap. Recently, the performance of the storage devices improved so fast that we cannot saturate the disk bandwidth with single logical CPU when do page swap out even on a high-end server machine. Because the performance of the storage device improved faster than that of single logical CPU. And it seems that the trend will not change in the near future. On the other hand, the THP becomes more and more popular because of increased memory size. So it becomes necessary to optimize THP swap performance. The advantages of the THP swap support include: - Batch the swap operations for the THP to reduce lock acquiring/releasing, including allocating/freeing the swap space, adding/deleting to/from the swap cache, and writing/reading the swap space, etc. This will help improve the performance of the THP swap. - The THP swap space read/write will be 2M sequential IO. It is particularly helpful for the swap read, which are usually 4k random IO. This will improve the performance of the THP swap too. - It will help the memory fragmentation, especially when the THP is heavily used by the applications. The 2M continuous pages will be free up after THP swapping out. - It will improve the THP utilization on the system with the swap turned on. Because the speed for khugepaged to collapse the normal pages into the THP is quite slow. After the THP is split during the swapping out, it will take quite long time for the normal pages to collapse back into the THP after being swapped in. The high THP utilization helps the efficiency of the page based memory management too. There are some concerns regarding THP swap in, mainly because possible enlarged read/write IO size (for swap in/out) may put more overhead on the storage device. To deal with that, the THP swap in should be turned on only when necessary. For example, it can be selected via "always/never/madvise" logic, to be turned on globally, turned off globally, or turned on only for VMA with MADV_HUGEPAGE, etc. This patchset is the first step for the THP swap support. The plan is to delay splitting THP step by step, finally avoid splitting THP during the THP swapping out and swap out/in the THP as a whole. As the first step, in this patchset, the splitting huge page is delayed from almost the first step of swapping out to after allocating the swap space for the THP and adding the THP into the swap cache. This will reduce lock acquiring/releasing for the locks used for the swap cache management. With the patchset, the swap out throughput improves 15.5% (from about 3.73GB/s to about 4.31GB/s) in the vm-scalability swap-w-seq test case with 8 processes. The test is done on a Xeon E5 v3 system. The swap device used is a RAM simulated PMEM (persistent memory) device. To test the sequential swapping out, the test case creates 8 processes, which sequentially allocate and write to the anonymous pages until the RAM and part of the swap device is used up. This patch (of 5): In this patch, splitting huge page is delayed from almost the first step of swapping out to after allocating the swap space for the THP (Transparent Huge Page) and adding the THP into the swap cache. This will batch the corresponding operation, thus improve THP swap out throughput. This is the first step for the THP swap optimization. The plan is to delay splitting the THP step by step and avoid splitting the THP finally. In this patch, one swap cluster is used to hold the contents of each THP swapped out. So, the size of the swap cluster is changed to that of the THP (Transparent Huge Page) on x86_64 architecture (512). For other architectures which want such THP swap optimization, ARCH_USES_THP_SWAP_CLUSTER needs to be selected in the Kconfig file for the architecture. In effect, this will enlarge swap cluster size by 2 times on x86_64. Which may make it harder to find a free cluster when the swap space becomes fragmented. So that, this may reduce the continuous swap space allocation and sequential write in theory. The performance test in 0day shows no regressions caused by this. In the future of THP swap optimization, some information of the swapped out THP (such as compound map count) will be recorded in the swap_cluster_info data structure. The mem cgroup swap accounting functions are enhanced to support charge or uncharge a swap cluster backing a THP as a whole. The swap cluster allocate/free functions are added to allocate/free a swap cluster for a THP. A fair simple algorithm is used for swap cluster allocation, that is, only the first swap device in priority list will be tried to allocate the swap cluster. The function will fail if the trying is not successful, and the caller will fallback to allocate a single swap slot instead. This works good enough for normal cases. If the difference of the number of the free swap clusters among multiple swap devices is significant, it is possible that some THPs are split earlier than necessary. For example, this could be caused by big size difference among multiple swap devices. The swap cache functions is enhanced to support add/delete THP to/from the swap cache as a set of (HPAGE_PMD_NR) sub-pages. This may be enhanced in the future with multi-order radix tree. But because we will split the THP soon during swapping out, that optimization doesn't make much sense for this first step. The THP splitting functions are enhanced to support to split THP in swap cache during swapping out. The page lock will be held during allocating the swap cluster, adding the THP into the swap cache and splitting the THP. So in the code path other than swapping out, if the THP need to be split, the PageSwapCache(THP) will be always false. The swap cluster is only available for SSD, so the THP swap optimization in this patchset has no effect for HDD. [ying.huang@intel.com: fix two issues in THP optimize patch] Link: http://lkml.kernel.org/r/87k25ed8zo.fsf@yhuang-dev.intel.com [hannes@cmpxchg.org: extensive cleanups and simplifications, reduce code size] Link: http://lkml.kernel.org/r/20170515112522.32457-2-ying.huang@intel.com Signed-off-by: "Huang, Ying" <ying.huang@intel.com> Signed-off-by: Johannes Weiner <hannes@cmpxchg.org> Suggested-by: Andrew Morton <akpm@linux-foundation.org> [for config option] Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> [for changes in huge_memory.c and huge_mm.h] Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Ebru Akagunduz <ebru.akagunduz@gmail.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Michal Hocko <mhocko@kernel.org> Cc: Tejun Heo <tj@kernel.org> Cc: Hugh Dickins <hughd@google.com> Cc: Shaohua Li <shli@kernel.org> Cc: Minchan Kim <minchan@kernel.org> Cc: Rik van Riel <riel@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-05-08mm, swap: use kvzalloc to allocate some swap data structuresHuang Ying
Now vzalloc() is used in swap code to allocate various data structures, such as swap cache, swap slots cache, cluster info, etc. Because the size may be too large on some system, so that normal kzalloc() may fail. But using kzalloc() has some advantages, for example, less memory fragmentation, less TLB pressure, etc. So change the data structure allocation in swap code to use kvzalloc() which will try kzalloc() firstly, and fallback to vzalloc() if kzalloc() failed. In general, although kmalloc() will reduce the number of high-order pages in short term, vmalloc() will cause more pain for memory fragmentation in the long term. And the swap data structure allocation that is changed in this patch is expected to be long term allocation. From Dave Hansen: "for example, we have a two-page data structure. vmalloc() takes two effectively random order-0 pages, probably from two different 2M pages and pins them. That "kills" two 2M pages. kmalloc(), allocating two *contiguous* pages, will not cross a 2M boundary. That means it will only "kill" the possibility of a single 2M page. More 2M pages == less fragmentation. The allocation in this patch occurs during swap on time, which is usually done during system boot, so usually we have high opportunity to allocate the contiguous pages successfully. The allocation for swap_map[] in struct swap_info_struct is not changed, because that is usually quite large and vmalloc_to_page() is used for it. That makes it a little harder to change. Link: http://lkml.kernel.org/r/20170407064911.25447-1-ying.huang@intel.com Signed-off-by: Huang Ying <ying.huang@intel.com> Acked-by: Tim Chen <tim.c.chen@intel.com> Acked-by: Michal Hocko <mhocko@suse.com> Acked-by: Rik van Riel <riel@redhat.com> Cc: Dave Hansen <dave.hansen@intel.com> Cc: Hugh Dickins <hughd@google.com> Cc: Shaohua Li <shli@kernel.org> Cc: Minchan Kim <minchan@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-05-03mm/swapfile.c: fix swap space leak in error path of swap_free_entries()Huang Ying
In swapcache_free_entries(), if swap_info_get_cont() returns NULL, something wrong occurs for the swap entry. But we should still continue to free the following swap entries in the array instead of skip them to avoid swap space leak. This is just problem in error path, where system may be in an inconsistent state, but it is still good to fix it. Link: http://lkml.kernel.org/r/20170421124739.24534-1-ying.huang@intel.com Signed-off-by: "Huang, Ying" <ying.huang@intel.com> Acked-by: Tim Chen <tim.c.chen@linux.intel.com> Cc: Rik van Riel <riel@redhat.com> Cc: Hugh Dickins <hughd@google.com> Cc: Shaohua Li <shli@kernel.org> Cc: Minchan Kim <minchan@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-05-03mm, swap: avoid lock swap_avail_lock when held cluster lockHuang Ying
Cluster lock is used to protect the swap_cluster_info and corresponding elements in swap_info_struct->swap_map[]. But it is found that now in scan_swap_map_slots(), swap_avail_lock may be acquired when cluster lock is held. This does no good except making the locking more complex and improving the potential locking contention, because the swap_info_struct->lock is used to protect the data structure operated in the code already. Fix this via moving the corresponding operations in scan_swap_map_slots() out of cluster lock. Link: http://lkml.kernel.org/r/20170317064635.12792-3-ying.huang@intel.com Signed-off-by: "Huang, Ying" <ying.huang@intel.com> Acked-by: Tim Chen <tim.c.chen@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-05-03mm, swap: improve readability via make spin_lock/unlock balancedHuang Ying
This is just a cleanup patch, no functionality change. In cluster_list_add_tail(), spin_lock_nested() is used to lock the cluster, while unlock_cluster() is used to unlock the cluster. To improve the code readability, use spin_unlock() directly to unlock the cluster. Link: http://lkml.kernel.org/r/20170317064635.12792-2-ying.huang@intel.com Signed-off-by: "Huang, Ying" <ying.huang@intel.com> Acked-by: Tim Chen <tim.c.chen@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-05-03mm, swap: Fix a race in free_swap_and_cache()Huang Ying
Before using cluster lock in free_swap_and_cache(), the swap_info_struct->lock will be held during freeing the swap entry and acquiring page lock, so the page swap count will not change when testing page information later. But after using cluster lock, the cluster lock (or swap_info_struct->lock) will be held only during freeing the swap entry. So before acquiring the page lock, the page swap count may be changed in another thread. If the page swap count is not 0, we should not delete the page from the swap cache. This is fixed via checking page swap count again after acquiring the page lock. I found the race when I review the code, so I didn't trigger the race via a test program. If the race occurs for an anonymous page shared by multiple processes via fork, multiple pages will be allocated and swapped in from the swap device for the previously shared one page. That is, the user-visible runtime effect is more memory will be used and the access latency for the page will be higher, that is, the performance regression. Link: http://lkml.kernel.org/r/20170301143905.12846-1-ying.huang@intel.com Signed-off-by: "Huang, Ying" <ying.huang@intel.com> Cc: Hugh Dickins <hughd@google.com> Cc: Shaohua Li <shli@kernel.org> Cc: Minchan Kim <minchan@kernel.org> Cc: Rik van Riel <riel@redhat.com> Cc: Tim Chen <tim.c.chen@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-03-09mm: convert generic code to 5-level pagingKirill A. Shutemov
Convert all non-architecture-specific code to 5-level paging. It's mostly mechanical adding handling one more page table level in places where we deal with pud_t. Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Acked-by: Michal Hocko <mhocko@suse.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-03-02sched/headers: Prepare for new header dependencies before moving code to ↵Ingo Molnar
<linux/sched/task.h> We are going to split <linux/sched/task.h> out of <linux/sched.h>, which will have to be picked up from other headers and a couple of .c files. Create a trivial placeholder <linux/sched/task.h> file that just maps to <linux/sched.h> to make this patch obviously correct and bisectable. Include the new header in the files that are going to need it. Acked-by: Linus Torvalds <torvalds@linux-foundation.org> Cc: Mike Galbraith <efault@gmx.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: linux-kernel@vger.kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-03-02sched/headers: Prepare for new header dependencies before moving code to ↵Ingo Molnar
<linux/sched/mm.h> We are going to split <linux/sched/mm.h> out of <linux/sched.h>, which will have to be picked up from other headers and a couple of .c files. Create a trivial placeholder <linux/sched/mm.h> file that just maps to <linux/sched.h> to make this patch obviously correct and bisectable. The APIs that are going to be moved first are: mm_alloc() __mmdrop() mmdrop() mmdrop_async_fn() mmdrop_async() mmget_not_zero() mmput() mmput_async() get_task_mm() mm_access() mm_release() Include the new header in the files that are going to need it. Acked-by: Linus Torvalds <torvalds@linux-foundation.org> Cc: Mike Galbraith <efault@gmx.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: linux-kernel@vger.kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-02-27mm: use mmget_not_zero() helperVegard Nossum
We already have the helper, we can convert the rest of the kernel mechanically using: git grep -l 'atomic_inc_not_zero.*mm_users' | xargs sed -i 's/atomic_inc_not_zero(&\(.*\)->mm_users)/mmget_not_zero\(\1\)/' This is needed for a later patch that hooks into the helper, but might be a worthwhile cleanup on its own. Link: http://lkml.kernel.org/r/20161218123229.22952-3-vegard.nossum@oracle.com Signed-off-by: Vegard Nossum <vegard.nossum@oracle.com> Acked-by: Michal Hocko <mhocko@suse.com> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: David Rientjes <rientjes@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-02-27mm: add new mmget() helperVegard Nossum
Apart from adding the helper function itself, the rest of the kernel is converted mechanically using: git grep -l 'atomic_inc.*mm_users' | xargs sed -i 's/atomic_inc(&\(.*\)->mm_users);/mmget\(\1\);/' git grep -l 'atomic_inc.*mm_users' | xargs sed -i 's/atomic_inc(&\(.*\)\.mm_users);/mmget\(\&\1\);/' This is needed for a later patch that hooks into the helper, but might be a worthwhile cleanup on its own. (Michal Hocko provided most of the kerneldoc comment.) Link: http://lkml.kernel.org/r/20161218123229.22952-2-vegard.nossum@oracle.com Signed-off-by: Vegard Nossum <vegard.nossum@oracle.com> Acked-by: Michal Hocko <mhocko@suse.com> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: David Rientjes <rientjes@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-02-22mm/swap: enable swap slots cache usageTim Chen
Initialize swap slots cache and enable it on swap on. Drain all swap slots on swap off. Link: http://lkml.kernel.org/r/07cbc94882fa95d4ac3cfc50b8dce0b1ec231b93.1484082593.git.tim.c.chen@linux.intel.com Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com> Cc: "Huang, Ying" <ying.huang@intel.com> Cc: Aaron Lu <aaron.lu@intel.com> Cc: Andi Kleen <ak@linux.intel.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Christian Borntraeger <borntraeger@de.ibm.com> Cc: Dave Hansen <dave.hansen@intel.com> Cc: Hillf Danton <hillf.zj@alibaba-inc.com> Cc: Huang Ying <ying.huang@intel.com> Cc: Hugh Dickins <hughd@google.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Jonathan Corbet <corbet@lwn.net> escreveu: Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Michal Hocko <mhocko@kernel.org> Cc: Minchan Kim <minchan@kernel.org> Cc: Rik van Riel <riel@redhat.com> Cc: Shaohua Li <shli@kernel.org> Cc: Vladimir Davydov <vdavydov.dev@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-02-22mm/swap: add cache for swap slots allocationTim Chen
We add per cpu caches for swap slots that can be allocated and freed quickly without the need to touch the swap info lock. Two separate caches are maintained for swap slots allocated and swap slots returned. This is to allow the swap slots to be returned to the global pool in a batch so they will have a chance to be coaelesced with other slots in a cluster. We do not reuse the slots that are returned right away, as it may increase fragmentation of the slots. The swap allocation cache is protected by a mutex as we may sleep when searching for empty slots in cache. The swap free cache is protected by a spin lock as we cannot sleep in the free path. We refill the swap slots cache when we run out of slots, and we disable the swap slots cache and drain the slots if the global number of slots fall below a low watermark threshold. We re-enable the cache agian when the slots available are above a high watermark. [ying.huang@intel.com: use raw_cpu_ptr over this_cpu_ptr for swap slots access] [tim.c.chen@linux.intel.com: add comments on locks in swap_slots.h] Link: http://lkml.kernel.org/r/20170118180327.GA24225@linux.intel.com Link: http://lkml.kernel.org/r/35de301a4eaa8daa2977de6e987f2c154385eb66.1484082593.git.tim.c.chen@linux.intel.com Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com> Signed-off-by: "Huang, Ying" <ying.huang@intel.com> Reviewed-by: Michal Hocko <mhocko@suse.com> Cc: Aaron Lu <aaron.lu@intel.com> Cc: Andi Kleen <ak@linux.intel.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Christian Borntraeger <borntraeger@de.ibm.com> Cc: Dave Hansen <dave.hansen@intel.com> Cc: Hillf Danton <hillf.zj@alibaba-inc.com> Cc: Huang Ying <ying.huang@intel.com> Cc: Hugh Dickins <hughd@google.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Jonathan Corbet <corbet@lwn.net> escreveu: Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Minchan Kim <minchan@kernel.org> Cc: Rik van Riel <riel@redhat.com> Cc: Shaohua Li <shli@kernel.org> Cc: Vladimir Davydov <vdavydov.dev@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-02-22mm/swap: free swap slots in batchTim Chen
Add new functions that free unused swap slots in batches without the need to reacquire swap info lock. This improves scalability and reduce lock contention. Link: http://lkml.kernel.org/r/c25e0fcdfd237ec4ca7db91631d3b9f6ed23824e.1484082593.git.tim.c.chen@linux.intel.com Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com> Signed-off-by: "Huang, Ying" <ying.huang@intel.com> Cc: Aaron Lu <aaron.lu@intel.com> Cc: Andi Kleen <ak@linux.intel.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Christian Borntraeger <borntraeger@de.ibm.com> Cc: Dave Hansen <dave.hansen@intel.com> Cc: Hillf Danton <hillf.zj@alibaba-inc.com> Cc: Huang Ying <ying.huang@intel.com> Cc: Hugh Dickins <hughd@google.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Jonathan Corbet <corbet@lwn.net> escreveu: Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Michal Hocko <mhocko@kernel.org> Cc: Minchan Kim <minchan@kernel.org> Cc: Rik van Riel <riel@redhat.com> Cc: Shaohua Li <shli@kernel.org> Cc: Vladimir Davydov <vdavydov.dev@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-02-22mm/swap: allocate swap slots in batchesTim Chen
Currently, the swap slots are allocated one page at a time, causing contention to the swap_info lock protecting the swap partition on every page being swapped. This patch adds new functions get_swap_pages and scan_swap_map_slots to request multiple swap slots at once. This will reduces the lock contention on the swap_info lock. Also scan_swap_map_slots can operate more efficiently as swap slots often occurs in clusters close to each other on a swap device and it is quicker to allocate them together. Link: http://lkml.kernel.org/r/9fec2845544371f62c3763d43510045e33d286a6.1484082593.git.tim.c.chen@linux.intel.com Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com> Signed-off-by: "Huang, Ying" <ying.huang@intel.com> Cc: Aaron Lu <aaron.lu@intel.com> Cc: Andi Kleen <ak@linux.intel.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Christian Borntraeger <borntraeger@de.ibm.com> Cc: Dave Hansen <dave.hansen@intel.com> Cc: Hillf Danton <hillf.zj@alibaba-inc.com> Cc: Huang Ying <ying.huang@intel.com> Cc: Hugh Dickins <hughd@google.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Jonathan Corbet <corbet@lwn.net> escreveu: Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Michal Hocko <mhocko@kernel.org> Cc: Minchan Kim <minchan@kernel.org> Cc: Rik van Riel <riel@redhat.com> Cc: Shaohua Li <shli@kernel.org> Cc: Vladimir Davydov <vdavydov.dev@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-02-22mm/swap: skip readahead for unreferenced swap slotsTim Chen
We can avoid needlessly allocating page for swap slots that are not used by anyone. No pages have to be read in for these slots. Link: http://lkml.kernel.org/r/0784b3f20b9bd3aa5552219624cb78dc4ae710c9.1484082593.git.tim.c.chen@linux.intel.com Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com> Signed-off-by: "Huang, Ying" <ying.huang@intel.com> Cc: Aaron Lu <aaron.lu@intel.com> Cc: Andi Kleen <ak@linux.intel.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Christian Borntraeger <borntraeger@de.ibm.com> Cc: Dave Hansen <dave.hansen@intel.com> Cc: Hillf Danton <hillf.zj@alibaba-inc.com> Cc: Huang Ying <ying.huang@intel.com> Cc: Hugh Dickins <hughd@google.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Jonathan Corbet <corbet@lwn.net> escreveu: Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Michal Hocko <mhocko@kernel.org> Cc: Minchan Kim <minchan@kernel.org> Cc: Rik van Riel <riel@redhat.com> Cc: Shaohua Li <shli@kernel.org> Cc: Vladimir Davydov <vdavydov.dev@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-02-22mm/swap: split swap cache into 64MB trunksHuang, Ying
The patch is to improve the scalability of the swap out/in via using fine grained locks for the swap cache. In current kernel, one address space will be used for each swap device. And in the common configuration, the number of the swap device is very small (one is typical). This causes the heavy lock contention on the radix tree of the address space if multiple tasks swap out/in concurrently. But in fact, there is no dependency between pages in the swap cache. So that, we can split the one shared address space for each swap device into several address spaces to reduce the lock contention. In the patch, the shared address space is split into 64MB trunks. 64MB is chosen to balance the memory space usage and effect of lock contention reduction. The size of struct address_space on x86_64 architecture is 408B, so with the patch, 6528B more memory will be used for every 1GB swap space on x86_64 architecture. One address space is still shared for the swap entries in the same 64M trunks. To avoid lock contention for the first round of swap space allocation, the order of the swap clusters in the initial free clusters list is changed. The swap space distance between the consecutive swap clusters in the free cluster list is at least 64M. After the first round of allocation, the swap clusters are expected to be freed randomly, so the lock contention should be reduced effectively. Link: http://lkml.kernel.org/r/735bab895e64c930581ffb0a05b661e01da82bc5.1484082593.git.tim.c.chen@linux.intel.com Signed-off-by: "Huang, Ying" <ying.huang@intel.com> Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com> Cc: Aaron Lu <aaron.lu@intel.com> Cc: Andi Kleen <ak@linux.intel.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Christian Borntraeger <borntraeger@de.ibm.com> Cc: Dave Hansen <dave.hansen@intel.com> Cc: Hillf Danton <hillf.zj@alibaba-inc.com> Cc: Huang Ying <ying.huang@intel.com> Cc: Hugh Dickins <hughd@google.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Jonathan Corbet <corbet@lwn.net> escreveu: Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Michal Hocko <mhocko@kernel.org> Cc: Minchan Kim <minchan@kernel.org> Cc: Rik van Riel <riel@redhat.com> Cc: Shaohua Li <shli@kernel.org> Cc: Vladimir Davydov <vdavydov.dev@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-02-22mm/swap: add cluster lockHuang, Ying
This patch is to reduce the lock contention of swap_info_struct->lock via using a more fine grained lock in swap_cluster_info for some swap operations. swap_info_struct->lock is heavily contended if multiple processes reclaim pages simultaneously. Because there is only one lock for each swap device. While in common configuration, there is only one or several swap devices in the system. The lock protects almost all swap related operations. In fact, many swap operations only access one element of swap_info_struct->swap_map array. And there is no dependency between different elements of swap_info_struct->swap_map. So a fine grained lock can be used to allow parallel access to the different elements of swap_info_struct->swap_map. In this patch, a spinlock is added to swap_cluster_info to protect the elements of swap_info_struct->swap_map in the swap cluster and the fields of swap_cluster_info. This reduced locking contention for swap_info_struct->swap_map access greatly. Because of the added spinlock, the size of swap_cluster_info increases from 4 bytes to 8 bytes on the 64 bit and 32 bit system. This will use additional 4k RAM for every 1G swap space. Because the size of swap_cluster_info is much smaller than the size of the cache line (8 vs 64 on x86_64 architecture), there may be false cache line sharing between spinlocks in swap_cluster_info. To avoid the false sharing in the first round of the swap cluster allocation, the order of the swap clusters in the free clusters list is changed. So that, the swap_cluster_info sharing the same cache line will be placed as far as possible. After the first round of allocation, the order of the clusters in free clusters list is expected to be random. So the false sharing should be not serious. Compared with a previous implementation using bit_spin_lock, the sequential swap out throughput improved about 3.2%. Test was done on a Xeon E5 v3 system. The swap device used is a RAM simulated PMEM (persistent memory) device. To test the sequential swapping out, the test case created 32 processes, which sequentially allocate and write to the anonymous pages until the RAM and part of the swap device is used. [ying.huang@intel.com: v5] Link: http://lkml.kernel.org/r/878tqeuuic.fsf_-_@yhuang-dev.intel.com [minchan@kernel.org: initialize spinlock for swap_cluster_info] Link: http://lkml.kernel.org/r/1486434945-29753-1-git-send-email-minchan@kernel.org [hughd@google.com: annotate nested locking for cluster lock] Link: http://lkml.kernel.org/r/alpine.LSU.2.11.1702161050540.21773@eggly.anvils Link: http://lkml.kernel.org/r/dbb860bbd825b1aaba18988015e8963f263c3f0d.1484082593.git.tim.c.chen@linux.intel.com Signed-off-by: "Huang, Ying" <ying.huang@intel.com> Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com> Signed-off-by: Minchan Kim <minchan@kernel.org> Signed-off-by: Hugh Dickins <hughd@google.com> Cc: Aaron Lu <aaron.lu@intel.com> Cc: Andi Kleen <ak@linux.intel.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Christian Borntraeger <borntraeger@de.ibm.com> Cc: Dave Hansen <dave.hansen@intel.com> Cc: Hillf Danton <hillf.zj@alibaba-inc.com> Cc: Huang Ying <ying.huang@intel.com> Cc: Hugh Dickins <hughd@google.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Jonathan Corbet <corbet@lwn.net> escreveu: Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Michal Hocko <mhocko@kernel.org> Cc: Minchan Kim <minchan@kernel.org> Cc: Rik van Riel <riel@redhat.com> Cc: Shaohua Li <shli@kernel.org> Cc: Vladimir Davydov <vdavydov.dev@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-02-22mm/swap: fix kernel message in swap_info_get()Huang, Ying
Patch series "mm/swap: Regular page swap optimizations", v5. Times have changed. Coming generation of Solid state Block device latencies are getting down to sub 100 usec, which is within an order of magnitude of DRAM, and their performance is orders of magnitude higher than the single- spindle rotational media we've swapped to historically. This could benefit many usage scenearios. For example cloud providers who overcommit their memory (as VM don't use all the memory provisioned). Having a fast swap will allow them to be more aggressive in memory overcommit and fit more VMs to a platform. In our testing [see footnote], the median latency that the kernel adds to a page fault is 15 usec, which comes quite close to the amount that will be contributed by the underlying I/O devices. The software latency comes mostly from contentions on the locks protecting the radix tree of the swap cache and also the locks protecting the individual swap devices. The lock contentions already consumed 35% of cpu cycles in our test. In the very near future, software latency will become the bottleneck to swap performnace as block device I/O latency gets within the shouting distance of DRAM speed. This patch set, reduced the median page fault latency from 15 usec to 4 usec (375% reduction) for DRAM based pmem block device. This patch (of 9): swap_info_get() is used not only in swap free code path but also in page_swapcount(), etc. So the original kernel message in swap_info_get() is not correct now. Fix it via replacing "swap_free" to "swap_info_get" in the message. Link: http://lkml.kernel.org/r/9b5f8bd6266f9da978c373f2384c8044df5e262c.1484082593.git.tim.c.chen@linux.intel.com Signed-off-by: "Huang, Ying" <ying.huang@intel.com> Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com> Reviewed-by: Rik van Riel <riel@redhat.com> Cc: Aaron Lu <aaron.lu@intel.com> Cc: Andi Kleen <ak@linux.intel.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Christian Borntraeger <borntraeger@de.ibm.com> Cc: Dave Hansen <dave.hansen@intel.com> Cc: Hillf Danton <hillf.zj@alibaba-inc.com> Cc: Huang Ying <ying.huang@intel.com> Cc: Hugh Dickins <hughd@google.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Jonathan Corbet <corbet@lwn.net> escreveu: Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Michal Hocko <mhocko@kernel.org> Cc: Minchan Kim <minchan@kernel.org> Cc: Shaohua Li <shli@kernel.org> Cc: Vladimir Davydov <vdavydov.dev@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-01-10mm: support anonymous stable pageMinchan Kim
During developemnt for zram-swap asynchronous writeback, I found strange corruption of compressed page, resulting in: Modules linked in: zram(E) CPU: 3 PID: 1520 Comm: zramd-1 Tainted: G E 4.8.0-mm1-00320-ge0d4894c9c38-dirty #3274 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Ubuntu-1.8.2-1ubuntu1 04/01/2014 task: ffff88007620b840 task.stack: ffff880078090000 RIP: set_freeobj.part.43+0x1c/0x1f RSP: 0018:ffff880078093ca8 EFLAGS: 00010246 RAX: 0000000000000018 RBX: ffff880076798d88 RCX: ffffffff81c408c8 RDX: 0000000000000018 RSI: 0000000000000000 RDI: 0000000000000246 RBP: ffff880078093cb0 R08: 0000000000000000 R09: 0000000000000000 R10: ffff88005bc43030 R11: 0000000000001df3 R12: ffff880076798d88 R13: 000000000005bc43 R14: ffff88007819d1b8 R15: 0000000000000001 FS: 0000000000000000(0000) GS:ffff88007e380000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007fc934048f20 CR3: 0000000077b01000 CR4: 00000000000406e0 Call Trace: obj_malloc+0x22b/0x260 zs_malloc+0x1e4/0x580 zram_bvec_rw+0x4cd/0x830 [zram] page_requests_rw+0x9c/0x130 [zram] zram_thread+0xe6/0x173 [zram] kthread+0xca/0xe0 ret_from_fork+0x25/0x30 With investigation, it reveals currently stable page doesn't support anonymous page. IOW, reuse_swap_page can reuse the page without waiting writeback completion so it can overwrite page zram is compressing. Unfortunately, zram has used per-cpu stream feature from v4.7. It aims for increasing cache hit ratio of scratch buffer for compressing. Downside of that approach is that zram should ask memory space for compressed page in per-cpu context which requires stricted gfp flag which could be failed. If so, it retries to allocate memory space out of per-cpu context so it could get memory this time and compress the data again, copies it to the memory space. In this scenario, zram assumes the data should never be changed but it is not true unless stable page supports. So, If the data is changed under us, zram can make buffer overrun because second compression size could be bigger than one we got in previous trial and blindly, copy bigger size object to smaller buffer which is buffer overrun. The overrun breaks zsmalloc free object chaining so system goes crash like above. I think below is same problem. https://bugzilla.suse.com/show_bug.cgi?id=997574 Unfortunately, reuse_swap_page should be atomic so that we cannot wait on writeback in there so the approach in this patch is simply return false if we found it needs stable page. Although it increases memory footprint temporarily, it happens rarely and it should be reclaimed easily althoug it happened. Also, It would be better than waiting of IO completion, which is critial path for application latency. Fixes: da9556a2367c ("zram: user per-cpu compression streams") Link: http://lkml.kernel.org/r/20161120233015.GA14113@bbox Link: http://lkml.kernel.org/r/1482366980-3782-2-git-send-email-minchan@kernel.org Signed-off-by: Minchan Kim <minchan@kernel.org> Acked-by: Hugh Dickins <hughd@google.com> Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Cc: Darrick J. Wong <darrick.wong@oracle.com> Cc: Takashi Iwai <tiwai@suse.de> Cc: Hyeoncheol Lee <cheol.lee@lge.com> Cc: <yjay.kim@lge.com> Cc: Sangseok Lee <sangseok.lee@lge.com> Cc: <stable@vger.kernel.org> [4.7+] Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-12-12mm: add three more cond_resched() in swapoffHugh Dickins
Add a cond_resched() in the unuse_pmd_range() loop (so as to call it even when pmd none or trans_huge, like zap_pmd_range() does); and in the unuse_mm() loop (since that might skip over many vmas). shmem_unuse() and radix_tree_locate_item() look good enough already. Those were the obvious places, but in fact the stalls came from find_next_to_unuse(), which sometimes scans through many unused entries. Apply scan_swap_map()'s LATENCY_LIMIT of 256 there too; and only go off to test frontswap_map when a used entry is found. Link: http://lkml.kernel.org/r/alpine.LSU.2.11.1612052155140.13021@eggly.anvils Signed-off-by: Hugh Dickins <hughd@google.com> Reported-by: Eric Dumazet <edumazet@google.com> Cc: David Rientjes <rientjes@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-11-11swapfile: fix memory corruption via malformed swapfileJann Horn
When root activates a swap partition whose header has the wrong endianness, nr_badpages elements of badpages are swabbed before nr_badpages has been checked, leading to a buffer overrun of up to 8GB. This normally is not a security issue because it can only be exploited by root (more specifically, a process with CAP_SYS_ADMIN or the ability to modify a swap file/partition), and such a process can already e.g. modify swapped-out memory of any other userspace process on the system. Link: http://lkml.kernel.org/r/1477949533-2509-1-git-send-email-jann@thejh.net Signed-off-by: Jann Horn <jann@thejh.net> Acked-by: Kees Cook <keescook@chromium.org> Acked-by: Jerome Marchand <jmarchan@redhat.com> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Hugh Dickins <hughd@google.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-10-07mm, swap: use offset of swap entry as key of swap cacheHuang Ying
This patch is to improve the performance of swap cache operations when the type of the swap device is not 0. Originally, the whole swap entry value is used as the key of the swap cache, even though there is one radix tree for each swap device. If the type of the swap device is not 0, the height of the radix tree of the swap cache will be increased unnecessary, especially on 64bit architecture. For example, for a 1GB swap device on the x86_64 architecture, the height of the radix tree of the swap cache is 11. But if the offset of the swap entry is used as the key of the swap cache, the height of the radix tree of the swap cache is 4. The increased height causes unnecessary radix tree descending and increased cache footprint. This patch reduces the height of the radix tree of the swap cache via using the offset of the swap entry instead of the whole swap entry value as the key of the swap cache. In 32 processes sequential swap out test case on a Xeon E5 v3 system with RAM disk as swap, the lock contention for the spinlock of the swap cache is reduced from 20.15% to 12.19%, when the type of the swap device is 1. Use the whole swap entry as key, perf-profile.calltrace.cycles-pp._raw_spin_lock_irq.__add_to_swap_cache.add_to_swap_cache.add_to_swap.shrink_page_list: 10.37, perf-profile.calltrace.cycles-pp._raw_spin_lock_irqsave.__remove_mapping.shrink_page_list.shrink_inactive_list.shrink_node_memcg: 9.78, Use the swap offset as key, perf-profile.calltrace.cycles-pp._raw_spin_lock_irq.__add_to_swap_cache.add_to_swap_cache.add_to_swap.shrink_page_list: 6.25, perf-profile.calltrace.cycles-pp._raw_spin_lock_irqsave.__remove_mapping.shrink_page_list.shrink_inactive_list.shrink_node_memcg: 5.94, Link: http://lkml.kernel.org/r/1473270649-27229-1-git-send-email-ying.huang@intel.com Signed-off-by: "Huang, Ying" <ying.huang@intel.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Michal Hocko <mhocko@kernel.org> Cc: Vladimir Davydov <vdavydov.dev@gmail.com> Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: Hugh Dickins <hughd@google.com> Cc: Mel Gorman <mgorman@techsingularity.net> Cc: Minchan Kim <minchan@kernel.org> Cc: Aaron Lu <aaron.lu@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-10-07mm, swap: add swap_cluster_listHuang Ying
This is a code clean up patch without functionality changes. The swap_cluster_list data structure and its operations are introduced to provide some better encapsulation for the free cluster and discard cluster list operations. This avoid some code duplication, improved the code readability, and reduced the total line number. [akpm@linux-foundation.org: coding-style fixes] Link: http://lkml.kernel.org/r/1472067356-16004-1-git-send-email-ying.huang@intel.com Signed-off-by: "Huang, Ying" <ying.huang@intel.com> Acked-by: Minchan Kim <minchan@kernel.org> Acked-by: Rik van Riel <riel@redhat.com> Cc: Tim Chen <tim.c.chen@intel.com> Cc: Hugh Dickins <hughd@google.com> Cc: Shaohua Li <shli@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-09-19mm: fix the page_swap_info() BUG_ON checkSantosh Shilimkar
Commit 62c230bc1790 ("mm: add support for a filesystem to activate swap files and use direct_IO for writing swap pages") replaced the swap_aops dirty hook from __set_page_dirty_no_writeback() with swap_set_page_dirty(). For normal cases without these special SWP flags code path falls back to __set_page_dirty_no_writeback() so the behaviour is expected to be the same as before. But swap_set_page_dirty() makes use of the page_swap_info() helper to get the swap_info_struct to check for the flags like SWP_FILE, SWP_BLKDEV etc as desired for those features. This helper has BUG_ON(!PageSwapCache(page)) which is racy and safe only for the set_page_dirty_lock() path. For the set_page_dirty() path which is often needed for cases to be called from irq context, kswapd() can toggle the flag behind the back while the call is getting executed when system is low on memory and heavy swapping is ongoing. This ends up with undesired kernel panic. This patch just moves the check outside the helper to its users appropriately to fix kernel panic for the described path. Couple of users of helpers already take care of SwapCache condition so I skipped them. Link: http://lkml.kernel.org/r/1473460718-31013-1-git-send-email-santosh.shilimkar@oracle.com Signed-off-by: Santosh Shilimkar <santosh.shilimkar@oracle.com> Cc: Mel Gorman <mgorman@suse.de> Cc: Joe Perches <joe@perches.com> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Rik van Riel <riel@redhat.com> Cc: David S. Miller <davem@davemloft.net> Cc: Jens Axboe <axboe@fb.com> Cc: Michal Hocko <mhocko@suse.com> Cc: Hugh Dickins <hughd@google.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: <stable@vger.kernel.org> [4.7.x] Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-07-26mm, frontswap: convert frontswap_enabled to static keyVlastimil Babka
I have noticed that frontswap.h first declares "frontswap_enabled" as extern bool variable, and then overrides it with "#define frontswap_enabled (1)" for CONFIG_FRONTSWAP=Y or (0) when disabled. The bool variable isn't actually instantiated anywhere. This all looks like an unfinished attempt to make frontswap_enabled reflect whether a backend is instantiated. But in the current state, all frontswap hooks call unconditionally into frontswap.c just to check if frontswap_ops is non-NULL. This should at least be checked inline, but we can further eliminate the overhead when CONFIG_FRONTSWAP is enabled and no backend registered, using a static key that is initially disabled, and gets enabled only upon first backend registration. Thus, checks for "frontswap_enabled" are replaced with "frontswap_enabled()" wrapping the static key check. There are two exceptions: - xen's selfballoon_process() was testing frontswap_enabled in code guarded by #ifdef CONFIG_FRONTSWAP, which was effectively always true when reachable. The patch just removes this check. Using frontswap_enabled() does not sound correct here, as this can be true even without xen's own backend being registered. - in SYSCALL_DEFINE2(swapon), change the check to IS_ENABLED(CONFIG_FRONTSWAP) as it seems the bitmap allocation cannot currently be postponed until a backend is registered. This means that frontswap will still have some memory overhead by being configured, but without a backend. After the patch, we can expect that some functions in frontswap.c are called only when frontswap_ops is non-NULL. Change the checks there to VM_BUG_ONs. While at it, convert other BUG_ONs to VM_BUG_ONs as frontswap has been stable for some time. [akpm@linux-foundation.org: coding-style fixes] Link: http://lkml.kernel.org/r/1463152235-9717-1-git-send-email-vbabka@suse.cz Signed-off-by: Vlastimil Babka <vbabka@suse.cz> Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com> Cc: David Vrabel <david.vrabel@citrix.com> Cc: Juergen Gross <jgross@suse.com> Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-05-12mm: thp: calculate the mapcount correctly for THP pages during WP faultsAndrea Arcangeli
This will provide fully accuracy to the mapcount calculation in the write protect faults, so page pinning will not get broken by false positive copy-on-writes. total_mapcount() isn't the right calculation needed in reuse_swap_page(), so this introduces a page_trans_huge_mapcount() that is effectively the full accurate return value for page_mapcount() if dealing with Transparent Hugepages, however we only use the page_trans_huge_mapcount() during COW faults where it strictly needed, due to its higher runtime cost. This also provide at practical zero cost the total_mapcount information which is needed to know if we can still relocate the page anon_vma to the local vma. If page_trans_huge_mapcount() returns 1 we can reuse the page no matter if it's a pte or a pmd_trans_huge triggering the fault, but we can only relocate the page anon_vma to the local vma->anon_vma if we're sure it's only this "vma" mapping the whole THP physical range. Kirill A. Shutemov discovered the problem with moving the page anon_vma to the local vma->anon_vma in a previous version of this patch and another problem in the way page_move_anon_rmap() was called. Andrew Morton discovered that CONFIG_SWAP=n wouldn't build in a previous version, because reuse_swap_page must be a macro to call page_trans_huge_mapcount from swap.h, so this uses a macro again instead of an inline function. With this change at least it's a less dangerous usage than it was before, because "page" is used only once now, while with the previous code reuse_swap_page(page++) would have called page_mapcount on page+1 and it would have increased page twice instead of just once. Dean Luick noticed an uninitialized variable that could result in a rmap inefficiency for the non-THP case in a previous version. Mike Marciniszyn said: : Our RDMA tests are seeing an issue with memory locking that bisects to : commit 61f5d698cc97 ("mm: re-enable THP") : : The test program registers two rather large MRs (512M) and RDMA : writes data to a passive peer using the first and RDMA reads it back : into the second MR and compares that data. The sizes are chosen randomly : between 0 and 1024 bytes. : : The test will get through a few (<= 4 iterations) and then gets a : compare error. : : Tracing indicates the kernel logical addresses associated with the individual : pages at registration ARE correct , the data in the "RDMA read response only" : packets ARE correct. : : The "corruption" occurs when the packet crosse two pages that are not physically : contiguous. The second page reads back as zero in the program. : : It looks like the user VA at the point of the compare error no longer points to : the same physical address as was registered. : : This patch totally resolves the issue! Link: http://lkml.kernel.org/r/1462547040-1737-2-git-send-email-aarcange@redhat.com Signed-off-by: Andrea Arcangeli <aarcange@redhat.com> Reviewed-by: "Kirill A. Shutemov" <kirill@shutemov.name> Reviewed-by: Dean Luick <dean.luick@intel.com> Tested-by: Alex Williamson <alex.williamson@redhat.com> Tested-by: Mike Marciniszyn <mike.marciniszyn@intel.com> Tested-by: Josh Collier <josh.d.collier@intel.com> Cc: Marc Haber <mh+linux-kernel@zugschlus.de> Cc: <stable@vger.kernel.org> [4.5] Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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