linux-kernel - PATCH] xfs: use roundup_pow_of_two in xlog_write_log

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Message-ID: <CY8PR05MB93787EA896549E9F08766754CDF1A@CY8PR05MB9378.namprd05.prod.outlook.com>
Date:   Tue, 12 Sep 2023 14:17:13 +0800
From:   Wang Jianchao <jianchwa@...look.com>
To:     djwong@...nel.org
Cc:     linux-xfs@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: PATCH] xfs: use roundup_pow_of_two in xlog_write_log_records

In our production environment, we find that mounting a 500M and
clean /boot needs ~6 seconds sometimes. The one cause is that
xlog_write_log_records() uses ffs to decide the buffer size. It
can cause a lot of small IO easily when xlog_clear_stale_blocks()
needs to wrap around the end of log area and log head block is
not power of two. As xlog_write_log_records() has handled bigger
buffer very well, we can use roundup_pow_of_two instead of ffs to
decide buffer size.

Signed-off-by: Wang Jianchao <jianchwa@...look.com>
---
 fs/xfs/xfs_log_recover.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/xfs/xfs_log_recover.c b/fs/xfs/xfs_log_recover.c
index 82c81d20459d..9368fefe1d0a 100644
--- a/fs/xfs/xfs_log_recover.c
+++ b/fs/xfs/xfs_log_recover.c
@@ -1528,7 +1528,7 @@ xlog_write_log_records(
 	 * a smaller size.  We need to be able to write at least a
 	 * log sector, or we're out of luck.
 	 */
-	bufblks = 1 << ffs(blocks);
+	bufblks = roundup_pow_of_two(blocks);
 	while (bufblks > log->l_logBBsize)
 		bufblks >>= 1;
 	while (!(buffer = xlog_alloc_buffer(log, bufblks))) {
-- 
2.34.1