From ee50cc19d80e9b9a8283d1fb517a778faf2f6899 Mon Sep 17 00:00:00 2001 From: Mikulas Patocka Date: Wed, 26 May 2021 10:29:45 -0400 Subject: dm writecache: don't split bios when overwriting contiguous cache content If dm-writecache overwrites existing cached data, it splits the incoming bio into many block-sized bios. The I/O scheduler does merge these bios into one large request but this needless splitting and merging causes performance degradation. Fix this by avoiding bio splitting if the cache target area that is being overwritten is contiguous. Signed-off-by: Mikulas Patocka Signed-off-by: Mike Snitzer --- drivers/md/dm-writecache.c | 38 ++++++++++++++++++++++++++++++-------- 1 file changed, 30 insertions(+), 8 deletions(-) (limited to 'drivers/md') diff --git a/drivers/md/dm-writecache.c b/drivers/md/dm-writecache.c index aecc246ade26..a44007297e63 100644 --- a/drivers/md/dm-writecache.c +++ b/drivers/md/dm-writecache.c @@ -1360,14 +1360,18 @@ read_next_block: } else { do { bool found_entry = false; + bool search_used = false; if (writecache_has_error(wc)) goto unlock_error; e = writecache_find_entry(wc, bio->bi_iter.bi_sector, 0); if (e) { - if (!writecache_entry_is_committed(wc, e)) + if (!writecache_entry_is_committed(wc, e)) { + search_used = true; goto bio_copy; + } if (!WC_MODE_PMEM(wc) && !e->write_in_progress) { wc->overwrote_committed = true; + search_used = true; goto bio_copy; } found_entry = true; @@ -1404,13 +1408,31 @@ bio_copy: sector_t current_cache_sec = start_cache_sec + (bio_size >> SECTOR_SHIFT); while (bio_size < bio->bi_iter.bi_size) { - struct wc_entry *f = writecache_pop_from_freelist(wc, current_cache_sec); - if (!f) - break; - write_original_sector_seq_count(wc, f, bio->bi_iter.bi_sector + - (bio_size >> SECTOR_SHIFT), wc->seq_count); - writecache_insert_entry(wc, f); - wc->uncommitted_blocks++; + if (!search_used) { + struct wc_entry *f = writecache_pop_from_freelist(wc, current_cache_sec); + if (!f) + break; + write_original_sector_seq_count(wc, f, bio->bi_iter.bi_sector + + (bio_size >> SECTOR_SHIFT), wc->seq_count); + writecache_insert_entry(wc, f); + wc->uncommitted_blocks++; + } else { + struct wc_entry *f; + struct rb_node *next = rb_next(&e->rb_node); + if (!next) + break; + f = container_of(next, struct wc_entry, rb_node); + if (f != e + 1) + break; + if (read_original_sector(wc, f) != + read_original_sector(wc, e) + (wc->block_size >> SECTOR_SHIFT)) + break; + if (unlikely(f->write_in_progress)) + break; + if (writecache_entry_is_committed(wc, f)) + wc->overwrote_committed = true; + e = f; + } bio_size += wc->block_size; current_cache_sec += wc->block_size >> SECTOR_SHIFT; } -- cgit v1.2.3