> On 20 Nov 2019, at 21:13, Theodore Y. Ts'o <tytso@xxxxxxx> wrote:
>
> Hi Alex,
>
> A couple of comments. First, please separate this patch so that these
> two separate pieces of functionality can be reviewed and tested
> separately:
>
This is the first patch of the series.
Thanks, Alex
>From 81c4b3b5a17d94525bbc6d2d89b20f6618b05bc6 Mon Sep 17 00:00:00 2001
From: Alex Zhuravlev <bzzz@xxxxxxxxxxxxx>
Date: Thu, 21 Nov 2019 09:53:13 +0300
Subject: [PATCH 1/2] ext4: limit scanning for a good group
at first two rounds to prevent situation when 10x-100x thousand
of groups are scanned, especially non-initialized groups.
Signed-off-by: Alex Zhuravlev <bzzz@xxxxxxxxxxxxx>
---
fs/ext4/ext4.h | 2 ++
fs/ext4/mballoc.c | 14 ++++++++++++--
fs/ext4/sysfs.c | 4 ++++
3 files changed, 18 insertions(+), 2 deletions(-)
diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 03db3e71676c..d4e47fdad87c 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -1480,6 +1480,8 @@ struct ext4_sb_info {
/* where last allocation was done - for stream allocation */
unsigned long s_mb_last_group;
unsigned long s_mb_last_start;
+ unsigned int s_mb_toscan0;
+ unsigned int s_mb_toscan1;
/* stats for buddy allocator */
atomic_t s_bal_reqs; /* number of reqs with len > 1 */
diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index a3e2767bdf2f..cebd7d8df0b8 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -2098,7 +2098,7 @@ static int ext4_mb_good_group(struct ext4_allocation_context *ac,
static noinline_for_stack int
ext4_mb_regular_allocator(struct ext4_allocation_context *ac)
{
- ext4_group_t ngroups, group, i;
+ ext4_group_t ngroups, toscan, group, i;
int cr;
int err = 0, first_err = 0;
struct ext4_sb_info *sbi;
@@ -2169,7 +2169,15 @@ ext4_mb_regular_allocator(struct ext4_allocation_context *ac)
*/
group = ac->ac_g_ex.fe_group;
- for (i = 0; i < ngroups; group++, i++) {
+ /* limit number of groups to scan at the first two rounds
+ * when we hope to find something really good */
+ toscan = ngroups;
+ if (cr == 0)
+ toscan = sbi->s_mb_toscan0;
+ else if (cr == 1)
+ toscan = sbi->s_mb_toscan1;
+
+ for (i = 0; i < toscan; group++, i++) {
int ret = 0;
cond_resched();
/*
@@ -2872,6 +2880,8 @@ void ext4_process_freed_data(struct super_block *sb, tid_t commit_tid)
bio_put(discard_bio);
}
}
+ sbi->s_mb_toscan0 = 1024;
+ sbi->s_mb_toscan1 = 4096;
list_for_each_entry_safe(entry, tmp, &freed_data_list, efd_list)
ext4_free_data_in_buddy(sb, entry);
diff --git a/fs/ext4/sysfs.c b/fs/ext4/sysfs.c
index eb1efad0e20a..c96ee20f5487 100644
--- a/fs/ext4/sysfs.c
+++ b/fs/ext4/sysfs.c
@@ -198,6 +198,8 @@ EXT4_RO_ATTR_ES_UI(errors_count, s_error_count);
EXT4_ATTR(first_error_time, 0444, first_error_time);
EXT4_ATTR(last_error_time, 0444, last_error_time);
EXT4_ATTR(journal_task, 0444, journal_task);
+EXT4_RW_ATTR_SBI_UI(mb_toscan0, s_mb_toscan0);
+EXT4_RW_ATTR_SBI_UI(mb_toscan1, s_mb_toscan1);
static unsigned int old_bump_val = 128;
EXT4_ATTR_PTR(max_writeback_mb_bump, 0444, pointer_ui, &old_bump_val);
@@ -228,6 +230,8 @@ static struct attribute *ext4_attrs[] = {
ATTR_LIST(first_error_time),
ATTR_LIST(last_error_time),
ATTR_LIST(journal_task),
+ ATTR_LIST(mb_toscan0),
+ ATTR_LIST(mb_toscan1),
NULL,
};
ATTRIBUTE_GROUPS(ext4);
--
2.20.1
