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authorMikulas Patocka <mpatocka@redhat.com>2020-01-15 12:35:22 +0300
committerMike Snitzer <snitzer@redhat.com>2020-01-16 21:34:17 +0300
commitdcd195071f22d4770911ca46694ca398b6d5101d (patch)
treecaa113ebf22d61d9034bc36fee85cb81b6061f69 /drivers/md/dm-writecache.c
parentbe240ff5e402df49c4ddbcb0595ef96009239f6a (diff)
downloadlinux-dcd195071f22d4770911ca46694ca398b6d5101d.tar.xz
dm writecache: improve performance of large linear writes on SSDs
When dm-writecache is used with SSD as a cache device, it would submit a separate bio for each written block. The I/Os would be merged by the disk scheduler, but this merging degrades performance. Improve dm-writecache performance by submitting larger bios - this is possible as long as there is consecutive free space on the cache device. Benchmark (arm64 with 64k page size, using /dev/ram0 as a cache device): fio --bs=512k --iodepth=32 --size=400M --direct=1 \ --filename=/dev/mapper/cache --rw=randwrite --numjobs=1 --name=test block old new size MiB/s MiB/s --------------------- 512 181 700 1k 347 1256 2k 644 2020 4k 1183 2759 8k 1852 3333 16k 2469 3509 32k 2974 3670 64k 3404 3810 Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Diffstat (limited to 'drivers/md/dm-writecache.c')
-rw-r--r--drivers/md/dm-writecache.c29
1 files changed, 25 insertions, 4 deletions
diff --git a/drivers/md/dm-writecache.c b/drivers/md/dm-writecache.c
index 9b0a3bf6a4a1..b9e27e37a943 100644
--- a/drivers/md/dm-writecache.c
+++ b/drivers/md/dm-writecache.c
@@ -625,7 +625,7 @@ static void writecache_add_to_freelist(struct dm_writecache *wc, struct wc_entry
wc->freelist_size++;
}
-static struct wc_entry *writecache_pop_from_freelist(struct dm_writecache *wc)
+static struct wc_entry *writecache_pop_from_freelist(struct dm_writecache *wc, sector_t expected_sector)
{
struct wc_entry *e;
@@ -634,6 +634,8 @@ static struct wc_entry *writecache_pop_from_freelist(struct dm_writecache *wc)
if (unlikely(!wc->current_free))
return NULL;
e = wc->current_free;
+ if (expected_sector != (sector_t)-1 && unlikely(cache_sector(wc, e) != expected_sector))
+ return NULL;
next = rb_next(&e->rb_node);
rb_erase(&e->rb_node, &wc->freetree);
if (unlikely(!next))
@@ -643,6 +645,8 @@ static struct wc_entry *writecache_pop_from_freelist(struct dm_writecache *wc)
if (unlikely(list_empty(&wc->freelist)))
return NULL;
e = container_of(wc->freelist.next, struct wc_entry, lru);
+ if (expected_sector != (sector_t)-1 && unlikely(cache_sector(wc, e) != expected_sector))
+ return NULL;
list_del(&e->lru);
}
wc->freelist_size--;
@@ -1193,7 +1197,7 @@ read_next_block:
goto bio_copy;
}
}
- e = writecache_pop_from_freelist(wc);
+ e = writecache_pop_from_freelist(wc, (sector_t)-1);
if (unlikely(!e)) {
writecache_wait_on_freelist(wc);
continue;
@@ -1205,9 +1209,26 @@ bio_copy:
if (WC_MODE_PMEM(wc)) {
bio_copy_block(wc, bio, memory_data(wc, e));
} else {
- dm_accept_partial_bio(bio, wc->block_size >> SECTOR_SHIFT);
+ unsigned bio_size = wc->block_size;
+ sector_t start_cache_sec = cache_sector(wc, e);
+ 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++;
+ bio_size += wc->block_size;
+ current_cache_sec += wc->block_size >> SECTOR_SHIFT;
+ }
+
bio_set_dev(bio, wc->ssd_dev->bdev);
- bio->bi_iter.bi_sector = cache_sector(wc, e);
+ bio->bi_iter.bi_sector = start_cache_sec;
+ dm_accept_partial_bio(bio, bio_size >> SECTOR_SHIFT);
+
if (unlikely(wc->uncommitted_blocks >= wc->autocommit_blocks)) {
wc->uncommitted_blocks = 0;
queue_work(wc->writeback_wq, &wc->flush_work);