Messages in this thread | | | Subject | Re: [PATCH v2] vmscan: fix increasing nr_isolated incurred by putback unevictable pages | From | Vlastimil Babka <> | Date | Thu, 6 Aug 2015 14:21:38 +0200 |
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On 08/05/2015 02:52 AM, Jaewon Kim wrote: > > > On 2015년 08월 05일 08:31, Minchan Kim wrote: >> Hello, >> >> On Tue, Aug 04, 2015 at 03:09:37PM -0700, Andrew Morton wrote: >>> On Tue, 04 Aug 2015 19:40:08 +0900 Jaewon Kim <jaewon31.kim@samsung.com> wrote: >>> >>>> reclaim_clean_pages_from_list() assumes that shrink_page_list() returns >>>> number of pages removed from the candidate list. But shrink_page_list() >>>> puts back mlocked pages without passing it to caller and without >>>> counting as nr_reclaimed. This incurrs increasing nr_isolated. >>>> To fix this, this patch changes shrink_page_list() to pass unevictable >>>> pages back to caller. Caller will take care those pages. >>>> >>>> .. >>>> >>>> --- a/mm/vmscan.c >>>> +++ b/mm/vmscan.c >>>> @@ -1157,7 +1157,7 @@ cull_mlocked: >>>> if (PageSwapCache(page)) >>>> try_to_free_swap(page); >>>> unlock_page(page); >>>> - putback_lru_page(page); >>>> + list_add(&page->lru, &ret_pages); >>>> continue; >>>> >>>> activate_locked: >>> >>> Is this going to cause a whole bunch of mlocked pages to be migrated >>> whereas in current kernels they stay where they are?
The only user that will see the change wrt migration is __alloc_contig_migrate_range() which is explicit about isolating mlocked page for migration (isolate_migratepages_range() calls isolate_migratepages_block() with ISOLATE_UNEVICTABLE). So this will make the migration work for clean page cache too.
>> >> >> It fixes two issues. >> >> 1. With unevictable page, cma_alloc will be successful. >> >> Exactly speaking, cma_alloc of current kernel will fail due to unevictable pages. >> >> 2. fix leaking of NR_ISOLATED counter of vmstat >> >> With it, too_many_isolated works. Otherwise, it could make hang until >> the process get SIGKILL.
This should be more explicit in the changelog. The first issue is not mentioned at all. The second is not clear from the description.
>> >> So, I think it's stable material. >> >> Acked-by: Minchan Kim <minchan@kernel.org>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
>> >> > Hello > > Traditional shrink_inactive_list will put back the unevictable pages as it does through putback_inactive_pages. > However as Minchan Kim said, cma_alloc will be more successful by migrating unevictable pages. > In current kernel, I think, cma_alloc is already trying to migrate unevictable pages except clean page cache. > This patch will allow clean page cache also to be migrated in cma_alloc. > > Thank you > > -- > To unsubscribe, send a message with 'unsubscribe linux-mm' in > the body to majordomo@kvack.org. For more info on Linux MM, > see: http://www.linux-mm.org/ . > Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a> >
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