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xfs: use roundup_pow_of_two instead of ffs during xlog_find_tail

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In our production environment, we find that mounting a 500M /boot
which is umount cleanly needs ~6s. One cause is that ffs() is
used by xlog_write_log_records() 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. Things are similar in xlog_find_verify_cycle().

The code is able to handed bigger buffer very well, we can use
roundup_pow_of_two() to replace ffs() directly to avoid small
and sychronous IOs.

Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Wang Jianchao <wangjc136@midea.com>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>
This commit is contained in:
Wang Jianchao 2023-09-13 09:38:01 +08:00 committed by Chandan Babu R
parent 1155b12edb
commit 8b010acb31
1 changed files with 2 additions and 2 deletions
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4
fs/xfs/xfs_log_recover.c
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@ -329,7 +329,7 @@ xlog_find_verify_cycle(
* try a smaller size. We need to be able to read at least
* a log sector, or we're out of luck.
*/
bufblks = 1 << ffs(nbblks);
bufblks = roundup_pow_of_two(nbblks);
while (bufblks > log->l_logBBsize)
bufblks >>= 1;
while (!(buffer = xlog_alloc_buffer(log, bufblks))) {
@ -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))) {