diff options
Diffstat (limited to 'Documentation/cgroups')
| -rw-r--r-- | Documentation/cgroups/memory.txt | 28 | ||||
| -rw-r--r-- | Documentation/cgroups/net_prio.txt | 53 |
2 files changed, 79 insertions, 2 deletions
diff --git a/Documentation/cgroups/memory.txt b/Documentation/cgroups/memory.txt index cc0ebc5241b3..4d8774f6f48a 100644 --- a/Documentation/cgroups/memory.txt +++ b/Documentation/cgroups/memory.txt @@ -44,8 +44,8 @@ Features: - oom-killer disable knob and oom-notifier - Root cgroup has no limit controls. - Kernel memory and Hugepages are not under control yet. We just manage - pages on LRU. To add more controls, we have to take care of performance. + Kernel memory support is work in progress, and the current version provides + basically functionality. (See Section 2.7) Brief summary of control files. @@ -72,6 +72,9 @@ Brief summary of control files. memory.oom_control # set/show oom controls. memory.numa_stat # show the number of memory usage per numa node + memory.kmem.tcp.limit_in_bytes # set/show hard limit for tcp buf memory + memory.kmem.tcp.usage_in_bytes # show current tcp buf memory allocation + 1. History The memory controller has a long history. A request for comments for the memory @@ -255,6 +258,27 @@ When oom event notifier is registered, event will be delivered. per-zone-per-cgroup LRU (cgroup's private LRU) is just guarded by zone->lru_lock, it has no lock of its own. +2.7 Kernel Memory Extension (CONFIG_CGROUP_MEM_RES_CTLR_KMEM) + +With the Kernel memory extension, the Memory Controller is able to limit +the amount of kernel memory used by the system. Kernel memory is fundamentally +different than user memory, since it can't be swapped out, which makes it +possible to DoS the system by consuming too much of this precious resource. + +Kernel memory limits are not imposed for the root cgroup. Usage for the root +cgroup may or may not be accounted. + +Currently no soft limit is implemented for kernel memory. It is future work +to trigger slab reclaim when those limits are reached. + +2.7.1 Current Kernel Memory resources accounted + +* sockets memory pressure: some sockets protocols have memory pressure +thresholds. The Memory Controller allows them to be controlled individually +per cgroup, instead of globally. + +* tcp memory pressure: sockets memory pressure for the tcp protocol. + 3. User Interface 0. Configuration diff --git a/Documentation/cgroups/net_prio.txt b/Documentation/cgroups/net_prio.txt new file mode 100644 index 000000000000..01b322635591 --- /dev/null +++ b/Documentation/cgroups/net_prio.txt @@ -0,0 +1,53 @@ +Network priority cgroup +------------------------- + +The Network priority cgroup provides an interface to allow an administrator to +dynamically set the priority of network traffic generated by various +applications + +Nominally, an application would set the priority of its traffic via the +SO_PRIORITY socket option. This however, is not always possible because: + +1) The application may not have been coded to set this value +2) The priority of application traffic is often a site-specific administrative + decision rather than an application defined one. + +This cgroup allows an administrator to assign a process to a group which defines +the priority of egress traffic on a given interface. Network priority groups can +be created by first mounting the cgroup filesystem. + +# mount -t cgroup -onet_prio none /sys/fs/cgroup/net_prio + +With the above step, the initial group acting as the parent accounting group +becomes visible at '/sys/fs/cgroup/net_prio'. This group includes all tasks in +the system. '/sys/fs/cgroup/net_prio/tasks' lists the tasks in this cgroup. + +Each net_prio cgroup contains two files that are subsystem specific + +net_prio.prioidx +This file is read-only, and is simply informative. It contains a unique integer +value that the kernel uses as an internal representation of this cgroup. + +net_prio.ifpriomap +This file contains a map of the priorities assigned to traffic originating from +processes in this group and egressing the system on various interfaces. It +contains a list of tuples in the form <ifname priority>. Contents of this file +can be modified by echoing a string into the file using the same tuple format. +for example: + +echo "eth0 5" > /sys/fs/cgroups/net_prio/iscsi/net_prio.ifpriomap + +This command would force any traffic originating from processes belonging to the +iscsi net_prio cgroup and egressing on interface eth0 to have the priority of +said traffic set to the value 5. The parent accounting group also has a +writeable 'net_prio.ifpriomap' file that can be used to set a system default +priority. + +Priorities are set immediately prior to queueing a frame to the device +queueing discipline (qdisc) so priorities will be assigned prior to the hardware +queue selection being made. + +One usage for the net_prio cgroup is with mqprio qdisc allowing application +traffic to be steered to hardware/driver based traffic classes. These mappings +can then be managed by administrators or other networking protocols such as +DCBX. |