This is a note to let you know that I've just added the patch titled
ext4: make mballoc try target group first even with mb_optimize_scan
to the 5.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
ext4-make-mballoc-try-target-group-first-even-with-mb_optimize_scan.patch
and it can be found in the queue-5.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 4fca50d440cc5d4dc570ad5484cc0b70b381bc2a Mon Sep 17 00:00:00 2001
From: Jan Kara <jack@xxxxxxx>
Date: Thu, 8 Sep 2022 11:21:24 +0200
Subject: ext4: make mballoc try target group first even with mb_optimize_scan
From: Jan Kara <jack@xxxxxxx>
commit 4fca50d440cc5d4dc570ad5484cc0b70b381bc2a upstream.
One of the side-effects of mb_optimize_scan was that the optimized
functions to select next group to try were called even before we tried
the goal group. As a result we no longer allocate files close to
corresponding inodes as well as we don't try to expand currently
allocated extent in the same group. This results in reaim regression
with workfile.disk workload of upto 8% with many clients on my test
machine:
baseline mb_optimize_scan
Hmean disk-1 2114.16 ( 0.00%) 2099.37 ( -0.70%)
Hmean disk-41 87794.43 ( 0.00%) 83787.47 * -4.56%*
Hmean disk-81 148170.73 ( 0.00%) 135527.05 * -8.53%*
Hmean disk-121 177506.11 ( 0.00%) 166284.93 * -6.32%*
Hmean disk-161 220951.51 ( 0.00%) 207563.39 * -6.06%*
Hmean disk-201 208722.74 ( 0.00%) 203235.59 ( -2.63%)
Hmean disk-241 222051.60 ( 0.00%) 217705.51 ( -1.96%)
Hmean disk-281 252244.17 ( 0.00%) 241132.72 * -4.41%*
Hmean disk-321 255844.84 ( 0.00%) 245412.84 * -4.08%*
Also this is causing huge regression (time increased by a factor of 5 or
so) when untarring archive with lots of small files on some eMMC storage
cards.
Fix the problem by making sure we try goal group first.
Fixes: 196e402adf2e ("ext4: improve cr 0 / cr 1 group scanning")
CC: stable@xxxxxxxxxx
Reported-and-tested-by: Stefan Wahren <stefan.wahren@xxxxxxxx>
Tested-by: Ojaswin Mujoo <ojaswin@xxxxxxxxxxxxx>
Reviewed-by: Ritesh Harjani (IBM) <ritesh.list@xxxxxxxxx>
Link: https://lore.kernel.org/all/20220727105123.ckwrhbilzrxqpt24@quack3/
Link: https://lore.kernel.org/all/0d81a7c2-46b7-6010-62a4-3e6cfc1628d6@xxxxxxxx/
Signed-off-by: Jan Kara <jack@xxxxxxx>
Link: https://lore.kernel.org/r/20220908092136.11770-1-jack@xxxxxxx
Signed-off-by: Theodore Ts'o <tytso@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/ext4/mballoc.c | 14 +++++++-------
1 file changed, 7 insertions(+), 7 deletions(-)
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -1052,8 +1052,10 @@ static void ext4_mb_choose_next_group(st
{
*new_cr = ac->ac_criteria;
- if (!should_optimize_scan(ac) || ac->ac_groups_linear_remaining)
+ if (!should_optimize_scan(ac) || ac->ac_groups_linear_remaining) {
+ *group = next_linear_group(ac, *group, ngroups);
return;
+ }
if (*new_cr == 0) {
ext4_mb_choose_next_group_cr0(ac, new_cr, group, ngroups);
@@ -2633,7 +2635,7 @@ static noinline_for_stack int
ext4_mb_regular_allocator(struct ext4_allocation_context *ac)
{
ext4_group_t prefetch_grp = 0, ngroups, group, i;
- int cr = -1;
+ int cr = -1, new_cr;
int err = 0, first_err = 0;
unsigned int nr = 0, prefetch_ios = 0;
struct ext4_sb_info *sbi;
@@ -2708,13 +2710,11 @@ repeat:
ac->ac_groups_linear_remaining = sbi->s_mb_max_linear_groups;
prefetch_grp = group;
- for (i = 0; i < ngroups; group = next_linear_group(ac, group, ngroups),
- i++) {
- int ret = 0, new_cr;
+ for (i = 0, new_cr = cr; i < ngroups; i++,
+ ext4_mb_choose_next_group(ac, &new_cr, &group, ngroups)) {
+ int ret = 0;
cond_resched();
-
- ext4_mb_choose_next_group(ac, &new_cr, &group, ngroups);
if (new_cr != cr) {
cr = new_cr;
goto repeat;
Patches currently in stable-queue which might be from jack@xxxxxxx are
queue-5.15/ext4-fix-bug-in-extents-parsing-when-eh_entries-0-and-eh_depth-0.patch
queue-5.15/ext4-make-mballoc-try-target-group-first-even-with-mb_optimize_scan.patch
