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Date: Thu, 19 May 2011 11:54:05 +0900 From: Minchan Kim <minchan.kim@...il.com> To: Andrew Lutomirski <luto@....edu>, KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> Cc: Wu Fengguang <fengguang.wu@...el.com>, Andi Kleen <andi@...stfloor.org>, "linux-mm@...ck.org" <linux-mm@...ck.org>, LKML <linux-kernel@...r.kernel.org>, KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>, Mel Gorman <mgorman@...e.de>, Johannes Weiner <hannes@...xchg.org>, Rik van Riel <riel@...hat.com> Subject: Re: Kernel falls apart under light memory pressure (i.e. linking vmlinux) On Thu, May 19, 2011 at 11:15 AM, Andrew Lutomirski <luto@....edu> wrote: > On Wed, May 18, 2011 at 1:17 AM, Minchan Kim <minchan.kim@...il.com> wrote: >> On Wed, May 18, 2011 at 4:22 AM, Andrew Lutomirski <luto@....edu> wrote: >>>> No, thanks. However it would be valuable if you can retry with this >>>> patch _alone_ (without the "if (need_resched()) return false;" change, >>>> as I don't see how it helps your case). >>>> >>>> @@ -2286,7 +2290,7 @@ static bool sleeping_prematurely(pg_data_t >>>> *pgdat, int order, long remaining, >>>> * must be balanced >>>> */ >>>> if (order) >>>> - return pgdat_balanced(pgdat, balanced, classzone_idx); >>>> + return !pgdat_balanced(pgdat, balanced, classzone_idx); >>>> else >>>> return !all_zones_ok; >>>> } >>> >>> Done. >>> >>> I logged in, added swap, and ran a program that allocated 1900MB of >>> RAM and memset it. The system lagged a bit but survived. kswapd >>> showed 10% CPU (which is odd, IMO, since I'm using aesni-intel and I >>> think that all the crypt happens in kworker when aesni-intel is in >>> use). >> >> I think kswapd could use 10% enough for reclaim. >> >>> >>> Then I started Firefox, loaded gmail, and ran test_mempressure.sh. >>> Kaboom! (I.e. system was hung) SysRq-F saved the system and produced >> >> Hang? >> It means you see softhangup of kswapd? or mouse/keyboard doesn't move? > > Mouse and keyboard dead. > >> Andrew, Could you test this patch with !pgdat_balanced patch? >> I think we shouldn't see OOM message if we have lots of free swap space. >> >> == CUT_HERE == >> diff --git a/mm/vmscan.c b/mm/vmscan.c >> index f73b865..cc23f04 100644 >> --- a/mm/vmscan.c >> +++ b/mm/vmscan.c >> @@ -1341,10 +1341,6 @@ static inline bool >> should_reclaim_stall(unsigned long nr_taken, >> if (current_is_kswapd()) >> return false; >> >> - /* Only stall on lumpy reclaim */ >> - if (sc->reclaim_mode & RECLAIM_MODE_SINGLE) >> - return false; >> - >> /* If we have relaimed everything on the isolated list, no stall */ >> if (nr_freed == nr_taken) >> return false; >> >> >> >> Then, if you don't see any unnecessary OOM but still see the hangup, >> could you apply this patch based on previous? > > With this patch, I started GNOME and Firefox, turned on swap, and ran > test_mempressure.sh 1500 1400 1. Instant panic (or OOPS and hang or > something -- didn't get the top part). Picture attached -- it looks > like memcg might be involved. I'm running F15, so it might even be > doing something. I cannot figure out why happens OOPS. Let me know your kernel version and config. Kame. Is there anything related to memcg you guess? In addition, the patch I give was utterly stupid. The goal is that we wait dirty page writeback in (order-0 | high priority) reclaim. (But I don't think it's ideal solution in this problem but just for proving the problem) But although we pass sync with 1 in set_reclaim_mode, it ignores. So fix is following as. (NOTICE: It doesn't related to your OOPS. ) But before further experiment, let's fix your oops. diff --git a/mm/vmscan.c b/mm/vmscan.c index 292582c..69d317e 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -311,7 +311,8 @@ static void set_reclaim_mode(int priority, struct scan_control *sc, */ if (sc->order > PAGE_ALLOC_COSTLY_ORDER) sc->reclaim_mode |= syncmode; - else if (sc->order && priority < DEF_PRIORITY - 2) + else if ((sc->order && priority < DEF_PRIORITY - 2) || + prioiry <= DEF_PRIORITY / 3) sc->reclaim_mode |= syncmode; else sc->reclaim_mode = RECLAIM_MODE_SINGLE | RECLAIM_MODE_ASYNC; @@ -1349,10 +1350,6 @@ static inline bool should_reclaim_stall(unsigned long nr_taken, if (current_is_kswapd()) return false; - /* Only stall on lumpy reclaim */ - if (sc->reclaim_mode & RECLAIM_MODE_SINGLE) - return false; - /* If we have relaimed everything on the isolated list, no stall */ if (nr_freed == nr_taken) return false; > > I won't be able to get netconsole dumps until next week because I'm > out of town and only have this one computer here. No problem. :) We should avoid OOPS for the experiment. > > I haven't tried the other patch. > > Also, the !pgdat_balanced fix plus the if (need_resched()) return > false patch just hung once on 2.6.37-rc9. I don't know what triggered Thanks for the good information. It seems need_resched patch isn't good candidate to fix current problem. We already weeded it out. Thank you very much for the testing! > it. Maybe yum. > > --Andy > -- Kind regards, Minchan Kim -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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