UbiquitousOS
/
OpenCloudOS-Kernel
mirror of https://gitee.com/OpenCloudOS/OpenCloudOS-Kernel.git
11
0
Fork 0
Code Issues Projects Releases Wiki Activity

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>
This commit is contained in:
Mikulas Patocka 2020-01-15 04:35:22 -05:00 committed by Mike Snitzer
parent be240ff5e4
commit dcd195071f
1 changed files with 25 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

29
drivers/md/dm-writecache.c
View File

@ -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);