diff mbox series

[1/2] mm/readahead: stop readahead loop if memcg charge fails

Message ID 20240201100835.1626685-2-liushixin2@huawei.com
State New
Headers
Series [1/2] mm/readahead: stop readahead loop if memcg charge fails |

Commit Message

Liu Shixin Feb. 1, 2024, 10:08 a.m. UTC 
  When a task in memcg readaheads file pages, page_cache_ra_unbounded()
will try to readahead nr_to_read pages. Even if the new allocated page
fails to charge, page_cache_ra_unbounded() still tries to readahead
next page. This leads to too much memory reclaim.

Stop readahead if mem_cgroup_charge() fails, i.e. add_to_page_cache_lru()
returns -ENOMEM.

Signed-off-by: Liu Shixin <liushixin2@huawei.com>
Signed-off-by: Jinjiang Tu <tujinjiang@huawei.com>
---
 mm/readahead.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

Comments

Jan Kara Feb. 1, 2024, 9:28 a.m. UTC | #1 
On Thu 01-02-24 18:08:34, Liu Shixin wrote:
> When a task in memcg readaheads file pages, page_cache_ra_unbounded()
> will try to readahead nr_to_read pages. Even if the new allocated page
> fails to charge, page_cache_ra_unbounded() still tries to readahead
> next page. This leads to too much memory reclaim.
> 
> Stop readahead if mem_cgroup_charge() fails, i.e. add_to_page_cache_lru()
> returns -ENOMEM.
> 
> Signed-off-by: Liu Shixin <liushixin2@huawei.com>
> Signed-off-by: Jinjiang Tu <tujinjiang@huawei.com>

Makes sense. Feel free to add:

Reviewed-by: Jan Kara <jack@suse.cz>

								Honza

> ---
>  mm/readahead.c | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/mm/readahead.c b/mm/readahead.c
> index 23620c57c1225..cc4abb67eb223 100644
> --- a/mm/readahead.c
> +++ b/mm/readahead.c
> @@ -228,6 +228,7 @@ void page_cache_ra_unbounded(struct readahead_control *ractl,
>  	 */
>  	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 readahead_control *ractl,
>  		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;
> -- 
> 2.25.1
>
Matthew Wilcox Feb. 1, 2024, 1:47 p.m. UTC | #2 
On Thu, Feb 01, 2024 at 06:08:34PM +0800, Liu Shixin wrote:
> @@ -247,9 +248,12 @@ void page_cache_ra_unbounded(struct readahead_control *ractl,
>  		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;

No, that's too early.  You've still got a batch of pages which were
successfully added; you have to read them.  You were only off by one
line though ;-)

>  			read_pages(ractl);
>  			ractl->_index++;
>  			i = ractl->_index + ractl->_nr_pages - index - 1;
> -- 
> 2.25.1
> 
>
Jan Kara Feb. 1, 2024, 1:52 p.m. UTC | #3 
On Thu 01-02-24 13:47:03, Matthew Wilcox wrote:
> On Thu, Feb 01, 2024 at 06:08:34PM +0800, Liu Shixin wrote:
> > @@ -247,9 +248,12 @@ void page_cache_ra_unbounded(struct readahead_control *ractl,
> >  		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;
> 
> No, that's too early.  You've still got a batch of pages which were
> successfully added; you have to read them.  You were only off by one
> line though ;-)

There's a read_pages() call just outside of the loop so this break is
actually fine AFAICT.

								Honza
Matthew Wilcox Feb. 1, 2024, 1:53 p.m. UTC | #4 
On Thu, Feb 01, 2024 at 02:52:31PM +0100, Jan Kara wrote:
> On Thu 01-02-24 13:47:03, Matthew Wilcox wrote:
> > On Thu, Feb 01, 2024 at 06:08:34PM +0800, Liu Shixin wrote:
> > > @@ -247,9 +248,12 @@ void page_cache_ra_unbounded(struct readahead_control *ractl,
> > >  		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;
> > 
> > No, that's too early.  You've still got a batch of pages which were
> > successfully added; you have to read them.  You were only off by one
> > line though ;-)
> 
> There's a read_pages() call just outside of the loop so this break is
> actually fine AFAICT.

Oh, good point!  I withdraw my criticism.
diff mbox series

Patch

diff --git a/mm/readahead.c b/mm/readahead.c
index 23620c57c1225..cc4abb67eb223 100644
--- a/mm/readahead.c
+++ b/mm/readahead.c
@@ -228,6 +228,7 @@  void page_cache_ra_unbounded(struct readahead_control *ractl,
 	 */
 	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 readahead_control *ractl,
 		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;