| Message ID | 20250402070934.2387587-1-weilongping@oppo.com (mailing list archive) |
|---|---|
| State | Accepted, archived |
| Delegated to: | Mikulas Patocka |
| Headers | show |
| Series | [1/2] dm-bufio: improve the performance of __dm_bufio_prefetch | expand |
On Wed, Apr 02, 2025 at 03:09:34PM +0800, LongPing Wei wrote: > 1. call blk_flush_plug when cache hit as the address of the subsequent > bio is no longer contiguous with the previous bio; > 2. skip cond_resched when ioprio class is rt; > > Signed-off-by: LongPing Wei <weilongping@oppo.com> > --- > drivers/md/dm-bufio.c | 5 ++++- > 1 file changed, 4 insertions(+), 1 deletion(-) Looks fine: Reviewed-by: Eric Biggers <ebiggers@kernel.org> But I do think the prefetching should be reworked to be along the lines of what I suggested here: https://lore.kernel.org/dm-devel/20250327170524.GF1425@sol.localdomain/ Any chance you're interested in helping with that? It also *might* be the case that the prefetching is no longer helpful and should just be removed. Especially if dm-verity will start prefetching the whole hash tree anyway, as your other patch does. - Eric
On 2025/4/3 1:43, Eric Biggers wrote: > On Wed, Apr 02, 2025 at 03:09:34PM +0800, LongPing Wei wrote: >> 1. call blk_flush_plug when cache hit as the address of the subsequent >> bio is no longer contiguous with the previous bio; >> 2. skip cond_resched when ioprio class is rt; >> >> Signed-off-by: LongPing Wei <weilongping@oppo.com> >> --- >> drivers/md/dm-bufio.c | 5 ++++- >> 1 file changed, 4 insertions(+), 1 deletion(-) > > Looks fine: > > Reviewed-by: Eric Biggers <ebiggers@kernel.org> > > But I do think the prefetching should be reworked to be along the lines of what > I suggested here: > https://lore.kernel.org/dm-devel/20250327170524.GF1425@sol.localdomain/ > Any chance you're interested in helping with that? > How about calling verity_prefetch_io directly in verity_map only when use_bh_wq return true for this dm io? The size of dm io may be a greate number as dm-verity doesn't set a max io length. Mikulas once mentioned that there was a problem that caused him to give up doing so. Has that issue been fixed? > It also *might* be the case that the prefetching is no longer helpful and should > just be removed. Especially if dm-verity will start prefetching the whole hash > tree anyway, as your other patch does. It seems that we cannot just removed the prefetching in verity_map as the cahche in dm-bufio may be shrinked. > > - Eric LongPing
This commit message is extremtly sparse. Not helped by the fact that the series also misses a cover letter. On Wed, Apr 02, 2025 at 03:09:34PM +0800, LongPing Wei wrote: > 1. call blk_flush_plug when cache hit as the address of the subsequent > bio is no longer contiguous with the previous bio; As you found out blk_flush_plug is not exported, and that for a good reason. This also completely fails to explain why you want to do this and what the measured benefit is. > 2. skip cond_resched when ioprio class is rt; Same here. Also these look compeltely unrelated and I have no idea why they are in the same patch.
diff --git a/drivers/md/dm-bufio.c b/drivers/md/dm-bufio.c index 9c8ed65cd87e..ec8392fbcf5d 100644 --- a/drivers/md/dm-bufio.c +++ b/drivers/md/dm-bufio.c @@ -1981,6 +1981,7 @@ static void __dm_bufio_prefetch(struct dm_bufio_client *c, unsigned short ioprio) { struct blk_plug plug; + unsigned short ioprio_class = IOPRIO_PRIO_CLASS(ioprio); LIST_HEAD(write_list); @@ -1997,6 +1998,7 @@ static void __dm_bufio_prefetch(struct dm_bufio_client *c, if (b) { /* already in cache */ cache_put_and_wake(c, b); + blk_flush_plug(&plug, false); continue; } @@ -2017,7 +2019,8 @@ static void __dm_bufio_prefetch(struct dm_bufio_client *c, submit_io(b, REQ_OP_READ, ioprio, read_endio); dm_bufio_release(b); - cond_resched(); + if (ioprio_class != IOPRIO_CLASS_RT) + cond_resched(); if (!n_blocks) goto flush_plug;
1. call blk_flush_plug when cache hit as the address of the subsequent bio is no longer contiguous with the previous bio; 2. skip cond_resched when ioprio class is rt; Signed-off-by: LongPing Wei <weilongping@oppo.com> --- drivers/md/dm-bufio.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)