commit a3d5dc908a5f572ce3e31fe83fd2459a1c3c5422
author Yang Yang <yang.yang29@zte.com.cn> Wed Jan 19 18:10:02 2022 -0800
committer Linus Torvalds <torvalds@linux-foundation.org> Thu Jan 20 08:52:55 2022 +0200
tree 4aa83c6a0edc2f7cfee7707ac32ae8f1e36c2659
parent e83a4472bf9f556d01984048e398e64246c4dd6f

delayacct: support swapin delay accounting for swapping without blkio

Currently delayacct accounts swapin delay only for swapping that cause
blkio.  If we use zram for swapping, tools/accounting/getdelays can't
get any SWAP delay.

It's useful to get zram swapin delay information, for example to adjust
compress algorithm or /proc/sys/vm/swappiness.

Reference to PSI, it accounts any kind of swapping by doing its work in
swap_readpage(), no matter whether swapping causes blkio.  Let delayacct
do the similar work.

Link: https://lkml.kernel.org/r/20211112083813.8559-1-yang.yang29@zte.com.cn
Signed-off-by: Yang Yang <yang.yang29@zte.com.cn>
Reported-by: Zeal Robot <zealci@zte.com.cn>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

kernel/delayacct.c

diff --git a/kernel/delayacct.c b/kernel/delayacct.c
index 51530d5..9769984 100644
--- a/kernel/delayacct.c
+++ b/kernel/delayacct.c
@@ -100,19 +100,10 @@ void __delayacct_blkio_start(void)
  */
 void __delayacct_blkio_end(struct task_struct *p)
 {
-	struct task_delay_info *delays = p->delays;
-	u64 *total;
-	u32 *count;
-
-	if (p->delays->flags & DELAYACCT_PF_SWAPIN) {
-		total = &delays->swapin_delay;
-		count = &delays->swapin_count;
-	} else {
-		total = &delays->blkio_delay;
-		count = &delays->blkio_count;
-	}
-
-	delayacct_end(&delays->lock, &delays->blkio_start, total, count);
+	delayacct_end(&p->delays->lock,
+		      &p->delays->blkio_start,
+		      &p->delays->blkio_delay,
+		      &p->delays->blkio_count);
 }
 
 int delayacct_add_tsk(struct taskstats *d, struct task_struct *tsk)
@@ -179,8 +170,7 @@ __u64 __delayacct_blkio_ticks(struct task_struct *tsk)
 	unsigned long flags;
 
 	raw_spin_lock_irqsave(&tsk->delays->lock, flags);
-	ret = nsec_to_clock_t(tsk->delays->blkio_delay +
-				tsk->delays->swapin_delay);
+	ret = nsec_to_clock_t(tsk->delays->blkio_delay);
 	raw_spin_unlock_irqrestore(&tsk->delays->lock, flags);
 	return ret;
 }
@@ -210,3 +200,16 @@ void __delayacct_thrashing_end(void)
 		      &current->delays->thrashing_delay,
 		      &current->delays->thrashing_count);
 }
+
+void __delayacct_swapin_start(void)
+{
+	current->delays->swapin_start = local_clock();
+}
+
+void __delayacct_swapin_end(void)
+{
+	delayacct_end(&current->delays->lock,
+		      &current->delays->swapin_start,
+		      &current->delays->swapin_delay,
+		      &current->delays->swapin_count);
+}