The patch titled Subject: mm: prevent addition of pages to swap if may_writepage is unset has been added to the -mm tree. Its filename is mm-prevent-addition-of-pages-to-swap-if-may_writepage-is-unset.patch Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/SubmitChecklist when testing your code *** The -mm tree is included into linux-next and is updated there every 3-4 working days ------------------------------------------------------ From: Minchan Kim <minchan@xxxxxxxxxx> Subject: mm: prevent addition of pages to swap if may_writepage is unset Recently, Luigi reported there are lots of free swap space when OOM happens. It's easily reproduced on zram-over-swap, where many instance of memory hogs are running and laptop_mode is enabled. Luigi reported there was no problem when he disabled laptop_mode. The problem when I investigate problem is following as. try_to_free_pages disable may_writepage if laptop_mode is enabled. shrink_page_list adds lots of anon pages in swap cache by add_to_swap, which makes pages Dirty and rotate them to head of inactive LRU without pageout. If it is repeated, inactive anon LRU is full of Dirty and SwapCache pages. In case of that, isolate_lru_pages fails because it try to isolate clean page due to may_writepage == 0. The may_writepage could be 1 only if total_scanned is higher than writeback_threshold in do_try_to_free_pages but unfortunately, VM can't isolate anon pages from inactive anon lru list by above reason and we already reclaimed all file-backed pages. So it ends up OOM killing. This patch prevents unnecessary addition of a page to swap cache when may_writepage is unset so anoymous lru list isn't full of Dirty/Swapcache page. So the VM can isolate pages from anon lru list, which ends up setting may_writepage to 1 and could swap out anon lru pages. When OOM triggers, I confirmed swap space was full. Signed-off-by: Minchan Kim <minchan@xxxxxxxxxx> Reported-by: Luigi Semenzato <semenzato@xxxxxxxxxx> Cc: Dan Magenheimer <dan.magenheimer@xxxxxxxxxx> Cc: Sonny Rao <sonnyrao@xxxxxxxxxx> Cc: Bryan Freed <bfreed@xxxxxxxxxx> Cc: Hugh Dickins <hughd@xxxxxxxxxx> Cc: Rik van Riel <riel@xxxxxxxxxx> Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx> Cc: Mel Gorman <mel@xxxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/vmscan.c | 2 ++ 1 file changed, 2 insertions(+) diff -puN mm/vmscan.c~mm-prevent-addition-of-pages-to-swap-if-may_writepage-is-unset mm/vmscan.c --- a/mm/vmscan.c~mm-prevent-addition-of-pages-to-swap-if-may_writepage-is-unset +++ a/mm/vmscan.c @@ -780,6 +780,8 @@ static unsigned long shrink_page_list(st if (PageAnon(page) && !PageSwapCache(page)) { if (!(sc->gfp_mask & __GFP_IO)) goto keep_locked; + if (!sc->may_writepage) + goto keep_locked; if (!add_to_swap(page)) goto activate_locked; may_enter_fs = 1; _ Patches currently in -mm which might be from minchan@xxxxxxxxxx are origin.patch mm-compaction-fix-echo-1-compact_memory-return-error-issue.patch mm-compaction-make-__compact_pgdat-and-compact_pgdat-return-void.patch mm-prevent-addition-of-pages-to-swap-if-may_writepage-is-unset.patch mm-forcibly-swapout-when-we-are-out-of-page-cache.patch mm-forcibly-swapout-when-we-are-out-of-page-cache-fix.patch mm-add-vm-event-counters-for-balloon-pages-compaction.patch block-aio-batch-completion-for-bios-kiocbs-fix-fix-fix-fix-fix.patch -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html