The patch titled
Subject: mm/readahead: break read-ahead loop if filemap_add_folio return -ENOMEM
has been added to the -mm mm-unstable branch. Its filename is
mm-readahead-break-read-ahead-loop-if-filemap_add_folio-return-enomem.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-readahead-break-read-ahead-loop-if-filemap_add_folio-return-enomem.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Liu Shixin <liushixin2@xxxxxxxxxx>
Subject: mm/readahead: break read-ahead loop if filemap_add_folio return -ENOMEM
Date: Fri, 22 Mar 2024 17:35:54 +0800
Patch series "Fix I/O high when memory almost met memcg limit", v2.
Recently, when install package in a docker which almost reached its memory
limit, the installer has no respond severely for more than 15 minutes.
During this period, I/O stays high(~1G/s) and influence the whole machine.
I've constructed a use case as follows:
1. create a docker:
$ cat test.sh
#!/bin/bash
docker rm centos7 --force
docker create --name centos7 --memory 4G --memory-swap 6G centos:7 /usr/sbin/init
docker start centos7
sleep 1
docker cp ./alloc_page centos7:/
docker cp ./reproduce.sh centos7:/
docker exec -it centos7 /bin/bash
2. try reproduce the problem in docker:
$ cat reproduce.sh
#!/bin/bash
while true; do
flag=$(ps -ef | grep -v grep | grep alloc_page| wc -l)
if [ "$flag" -eq 0 ]; then
/alloc_page &
fi
sleep 30
start_time=$(date +%s)
yum install -y expect > /dev/null 2>&1
end_time=$(date +%s)
elapsed_time=$((end_time - start_time))
echo "$elapsed_time seconds"
yum remove -y expect > /dev/null 2>&1
done
$ cat alloc_page.c:
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#define SIZE 1*1024*1024 //1M
int main()
{
void *addr = NULL;
int i;
for (i = 0; i < 1024 * 6 - 50;i++) {
addr = (void *)malloc(SIZE);
if (!addr)
return -1;
memset(addr, 0, SIZE);
}
sleep(99999);
return 0;
}
We found that this problem is caused by a lot ot meaningless read-ahead.
Since the docker is almost met memory limit, the page will be reclaimed
immediately after read-ahead and will read-ahead again immediately. The
program is executed slowly and waste a lot of I/O resource.
These two patch aim to break the read-ahead in above scenario.
[1] https://lore.kernel.org/linux-mm/c2f4a2fa-3bde-72ce-66f5-db81a373fdbc@xxxxxxxxxx/T/
[2] https://lore.kernel.org/all/20240201100835.1626685-1-liushixin2@xxxxxxxxxx/
[3] https://lore.kernel.org/all/20240201173130.frpaqpy7iyzias5j@quack3/
This patch (of 2):
When filemap_add_folio() return -ENOMEM, break read-ahead loop like what
filemap_alloc_folio() does.
Link: https://lkml.kernel.org/r/20240322093555.226789-1-liushixin2@xxxxxxxxxx
Link: https://lkml.kernel.org/r/20240322093555.226789-2-liushixin2@xxxxxxxxxx
Signed-off-by: Liu Shixin <liushixin2@xxxxxxxxxx>
Signed-off-by: Jinjiang Tu <tujinjiang@xxxxxxxxxx>
Reviewed-by: Jan Kara <jack@xxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Christian Brauner <brauner@xxxxxxxxxx>
Cc: Liu Shixin <liushixin2@xxxxxxxxxx>
Cc: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/readahead.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
--- a/mm/readahead.c~mm-readahead-break-read-ahead-loop-if-filemap_add_folio-return-enomem
+++ a/mm/readahead.c
@@ -228,6 +228,7 @@ void page_cache_ra_unbounded(struct read
*/
for (i = 0; i < nr_to_read; i++) {
struct folio *folio = xa_load(&mapping->i_pages, index + i);
+ int ret;
if (folio && !xa_is_value(folio)) {
/*
@@ -247,9 +248,12 @@ void page_cache_ra_unbounded(struct read
folio = filemap_alloc_folio(gfp_mask, 0);
if (!folio)
break;
- if (filemap_add_folio(mapping, folio, index + i,
- gfp_mask) < 0) {
+
+ ret = filemap_add_folio(mapping, folio, index + i, gfp_mask);
+ if (ret < 0) {
folio_put(folio);
+ if (ret == -ENOMEM)
+ break;
read_pages(ractl);
ractl->_index++;
i = ractl->_index + ractl->_nr_pages - index - 1;
_
Patches currently in -mm which might be from liushixin2@xxxxxxxxxx are
mm-readahead-break-read-ahead-loop-if-filemap_add_folio-return-enomem.patch
mm-readahead-dont-decrease-mmap_miss-when-folio-has-workingset-flags.patch
