* [dm-devel] [PATCH 0/1] dm writecache: commit just one block, not a full page
@ 2021-06-21 18:09 Mikulas Patocka
2021-06-21 18:09 ` [dm-devel] [PATCH 1/1] " Mikulas Patocka
0 siblings, 1 reply; 2+ messages in thread
From: Mikulas Patocka @ 2021-06-21 18:09 UTC (permalink / raw)
To: Mikulas Patocka, dm-devel, msnitzer
Hi Mike
I suggest to remove the patch 991bd8d7bc78966b4dc427b53a144f276bffcd52
("dm writecache: commit just one block, not a full page") from your
repository and replace it with this patch.
Sub-4k writes have poor performance with most SSDs, so we should make sure
that we write at least 4k.
Mikulas
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^ permalink raw reply [flat|nested] 2+ messages in thread
* [dm-devel] [PATCH 1/1] dm writecache: commit just one block, not a full page
2021-06-21 18:09 [dm-devel] [PATCH 0/1] dm writecache: commit just one block, not a full page Mikulas Patocka
@ 2021-06-21 18:09 ` Mikulas Patocka
0 siblings, 0 replies; 2+ messages in thread
From: Mikulas Patocka @ 2021-06-21 18:09 UTC (permalink / raw)
To: Mikulas Patocka, dm-devel, msnitzer
Some architectures have pages larger than 4k and committing a full page
causes needless overhead.
Fix this by writing a single block when committing the superblock.
Writes smaller than 4k are slow on most SSDs (because the SSD performs
read-modify-write internally), so make sure that we write at least 4k.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Index: linux-2.6/drivers/md/dm-writecache.c
===================================================================
--- linux-2.6.orig/drivers/md/dm-writecache.c
+++ linux-2.6/drivers/md/dm-writecache.c
@@ -532,7 +532,7 @@ static void ssd_commit_superblock(struct
region.bdev = wc->ssd_dev->bdev;
region.sector = 0;
- region.count = PAGE_SIZE >> SECTOR_SHIFT;
+ region.count = max(4096U, wc->block_size) >> SECTOR_SHIFT;
if (unlikely(region.sector + region.count > wc->metadata_sectors))
region.count = wc->metadata_sectors - region.sector;
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2021-06-21 18:09 [dm-devel] [PATCH 0/1] dm writecache: commit just one block, not a full page Mikulas Patocka
2021-06-21 18:09 ` [dm-devel] [PATCH 1/1] " Mikulas Patocka
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