[PATCH] block/psi: remove PSI annotations from submit_bio

[PATCH] block/psi: remove PSI annotations from submit_bio

[cgel.zte]

From: Yang Yang <yang.yang29@zte.com.cn>

psi tracks the time spent submitting the IO of refaulting pages[1].
But after we tracks refault stalls from swap_readpage[2][3], there
is no need to do so anymore. Since swap_readpage already includes
IO submitting time.

[1] commit b8e24a9300b0 ("block: annotate refault stalls from IO submission")
[2] commit 937790699be9 ("mm/page_io.c: annotate refault stalls from swap_readpage")
[3] commit 2b413a1a728f ("mm: page_io: fix psi memory pressure error on cold swapins")

Signed-off-by: Yang Yang <yang.yang29@zte.com.cn>
Reviewed-by: Ran Xiaokai <ran.xiaokai@zte.com.cn>
---
 block/bio.c               |  8 --------
 block/blk-core.c          | 17 -----------------
 fs/direct-io.c            |  2 --
 include/linux/blk_types.h |  1 -
 4 files changed, 28 deletions(-)

diff --git a/block/bio.c b/block/bio.c
index 3c57b3ba727d..efbbeed348e3 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -1034,9 +1034,6 @@ void __bio_add_page(struct bio *bio, struct page *page,
 
 	bio->bi_iter.bi_size += len;
 	bio->bi_vcnt++;
-
-	if (!bio_flagged(bio, BIO_WORKINGSET) && unlikely(PageWorkingset(page)))
-		bio_set_flag(bio, BIO_WORKINGSET);
 }
 EXPORT_SYMBOL_GPL(__bio_add_page);
 
@@ -1252,9 +1249,6 @@ static int __bio_iov_append_get_pages(struct bio *bio, struct iov_iter *iter)
  * fit into the bio, or are requested in @iter, whatever is smaller. If
  * MM encounters an error pinning the requested pages, it stops. Error
  * is returned only if 0 pages could be pinned.
- *
- * It's intended for direct IO, so doesn't do PSI tracking, the caller is
- * responsible for setting BIO_WORKINGSET if necessary.
  */
 int bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter)
 {
@@ -1273,8 +1267,6 @@ int bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter)
 			ret = __bio_iov_iter_get_pages(bio, iter);
 	} while (!ret && iov_iter_count(iter) && !bio_full(bio, 0));
 
-	/* don't account direct I/O as memory stall */
-	bio_clear_flag(bio, BIO_WORKINGSET);
 	return bio->bi_vcnt ? 0 : ret;
 }
 EXPORT_SYMBOL_GPL(bio_iov_iter_get_pages);
diff --git a/block/blk-core.c b/block/blk-core.c
index ddac62aebc55..faf7d950a4d5 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -37,7 +37,6 @@
 #include <linux/t10-pi.h>
 #include <linux/debugfs.h>
 #include <linux/bpf.h>
-#include <linux/psi.h>
 #include <linux/part_stat.h>
 #include <linux/sched/sysctl.h>
 #include <linux/blk-crypto.h>
@@ -911,22 +910,6 @@ void submit_bio(struct bio *bio)
 		}
 	}
 
-	/*
-	 * If we're reading data that is part of the userspace workingset, count
-	 * submission time as memory stall.  When the device is congested, or
-	 * the submitting cgroup IO-throttled, submission can be a significant
-	 * part of overall IO time.
-	 */
-	if (unlikely(bio_op(bio) == REQ_OP_READ &&
-	    bio_flagged(bio, BIO_WORKINGSET))) {
-		unsigned long pflags;
-
-		psi_memstall_enter(&pflags);
-		submit_bio_noacct(bio);
-		psi_memstall_leave(&pflags);
-		return;
-	}
-
 	submit_bio_noacct(bio);
 }
 EXPORT_SYMBOL(submit_bio);
diff --git a/fs/direct-io.c b/fs/direct-io.c
index aef06e607b40..5cac8c8869c5 100644
--- a/fs/direct-io.c
+++ b/fs/direct-io.c
@@ -419,8 +419,6 @@ static inline void dio_bio_submit(struct dio *dio, struct dio_submit *sdio)
 	unsigned long flags;
 
 	bio->bi_private = dio;
-	/* don't account direct I/O as memory stall */
-	bio_clear_flag(bio, BIO_WORKINGSET);
 
 	spin_lock_irqsave(&dio->bio_lock, flags);
 	dio->refcount++;
diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index 0c7a9a1f06c8..ab50c59b02ce 100644
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -314,7 +314,6 @@ enum {
 	BIO_NO_PAGE_REF,	/* don't put release vec pages */
 	BIO_CLONED,		/* doesn't own data */
 	BIO_BOUNCED,		/* bio is a bounce bio */
-	BIO_WORKINGSET,		/* contains userspace workingset pages */
 	BIO_QUIET,		/* Make BIO Quiet */
 	BIO_CHAIN,		/* chained bio, ->bi_remaining in effect */
 	BIO_REFFED,		/* bio has elevated ->bi_cnt */
-- 
2.25.1

Re: [PATCH] block/psi: remove PSI annotations from submit_bio

[Johannes Weiner]

On Wed, Mar 09, 2022 at 09:43:24AM +0000, cgel.zte@gmail.com wrote:
> From: Yang Yang <yang.yang29@zte.com.cn>
> 
> psi tracks the time spent submitting the IO of refaulting pages[1].
> But after we tracks refault stalls from swap_readpage[2][3], there
> is no need to do so anymore. Since swap_readpage already includes
> IO submitting time.
> 
> [1] commit b8e24a9300b0 ("block: annotate refault stalls from IO submission")
> [2] commit 937790699be9 ("mm/page_io.c: annotate refault stalls from swap_readpage")
> [3] commit 2b413a1a728f ("mm: page_io: fix psi memory pressure error on cold swapins")
> 
> Signed-off-by: Yang Yang <yang.yang29@zte.com.cn>
> Reviewed-by: Ran Xiaokai <ran.xiaokai@zte.com.cn>

It's still needed by file cache refaults!

NAK

Re: [PATCH] block/psi: remove PSI annotations from submit_bio

[Christoph Hellwig]

On Wed, Mar 09, 2022 at 02:18:19PM -0500, Johannes Weiner wrote:
> On Wed, Mar 09, 2022 at 09:43:24AM +0000, cgel.zte@gmail.com wrote:
> > From: Yang Yang <yang.yang29@zte.com.cn>
> > 
> > psi tracks the time spent submitting the IO of refaulting pages[1].
> > But after we tracks refault stalls from swap_readpage[2][3], there
> > is no need to do so anymore. Since swap_readpage already includes
> > IO submitting time.
> > 
> > [1] commit b8e24a9300b0 ("block: annotate refault stalls from IO submission")
> > [2] commit 937790699be9 ("mm/page_io.c: annotate refault stalls from swap_readpage")
> > [3] commit 2b413a1a728f ("mm: page_io: fix psi memory pressure error on cold swapins")
> > 
> > Signed-off-by: Yang Yang <yang.yang29@zte.com.cn>
> > Reviewed-by: Ran Xiaokai <ran.xiaokai@zte.com.cn>
> 
> It's still needed by file cache refaults!

Can we get proper annotations for those please?  These bio-level hooks are
horrible and a maintainance nightmware.

Re: [PATCH] block/psi: remove PSI annotations from submit_bio

[Johannes Weiner]

On Wed, Mar 09, 2022 at 10:46:52PM -0800, Christoph Hellwig wrote:
> On Wed, Mar 09, 2022 at 02:18:19PM -0500, Johannes Weiner wrote:
> > On Wed, Mar 09, 2022 at 09:43:24AM +0000, cgel.zte@gmail.com wrote:
> > > From: Yang Yang <yang.yang29@zte.com.cn>
> > > 
> > > psi tracks the time spent submitting the IO of refaulting pages[1].
> > > But after we tracks refault stalls from swap_readpage[2][3], there
> > > is no need to do so anymore. Since swap_readpage already includes
> > > IO submitting time.
> > > 
> > > [1] commit b8e24a9300b0 ("block: annotate refault stalls from IO submission")
> > > [2] commit 937790699be9 ("mm/page_io.c: annotate refault stalls from swap_readpage")
> > > [3] commit 2b413a1a728f ("mm: page_io: fix psi memory pressure error on cold swapins")
> > > 
> > > Signed-off-by: Yang Yang <yang.yang29@zte.com.cn>
> > > Reviewed-by: Ran Xiaokai <ran.xiaokai@zte.com.cn>
> > 
> > It's still needed by file cache refaults!
> 
> Can we get proper annotations for those please?  These bio-level hooks are
> horrible and a maintainance nightmware.

The first version did that, but it was sprawling and not well-received:

https://lkml.org/lkml/2019/7/22/1261

Re: [PATCH] block/psi: remove PSI annotations from submit_bio

[Christoph Hellwig]

On Thu, Mar 10, 2022 at 11:16:41AM -0500, Johannes Weiner wrote:
> The first version did that, but it was sprawling and not well-received:
> 
> https://lkml.org/lkml/2019/7/22/1261

Well, Dave's comments are spot on.  Except that we replaced it with
something even more horrible and not something sensible as he suggested.

Re: [PATCH] block/psi: remove PSI annotations from submit_bio

[Johannes Weiner]

On Thu, Mar 10, 2022 at 08:18:31AM -0800, Christoph Hellwig wrote:
> On Thu, Mar 10, 2022 at 11:16:41AM -0500, Johannes Weiner wrote:
> > The first version did that, but it was sprawling and not well-received:
> > 
> > https://lkml.org/lkml/2019/7/22/1261
> 
> Well, Dave's comments are spot on.  Except that we replaced it with
> something even more horrible and not something sensible as he suggested.

Confused. I changed it the way Dave suggested, to which he replied
"this is much cleaner and easier to maintain". Are we reading
different threads? Care to elaborate?

Re: [PATCH] block/psi: remove PSI annotations from submit_bio

[CGEL]

On Wed, Mar 09, 2022 at 02:18:19PM -0500, Johannes Weiner wrote:
> On Wed, Mar 09, 2022 at 09:43:24AM +0000, cgel.zte@gmail.com wrote:
> > From: Yang Yang <yang.yang29@zte.com.cn>
> > 
> > psi tracks the time spent submitting the IO of refaulting pages[1].
> > But after we tracks refault stalls from swap_readpage[2][3], there
> > is no need to do so anymore. Since swap_readpage already includes
> > IO submitting time.
> > 
> > [1] commit b8e24a9300b0 ("block: annotate refault stalls from IO submission")
> > [2] commit 937790699be9 ("mm/page_io.c: annotate refault stalls from swap_readpage")
> > [3] commit 2b413a1a728f ("mm: page_io: fix psi memory pressure error on cold swapins")
> > 
> > Signed-off-by: Yang Yang <yang.yang29@zte.com.cn>
> > Reviewed-by: Ran Xiaokai <ran.xiaokai@zte.com.cn>
> 
> It's still needed by file cache refaults!
> 
> NAK
What about submit_bio() only counts file cache refaults?
This will reduce redundant calling of psi_memstall_enter()
for swap_readpage().