On Sun, May 15, 2011 at 12:12:36PM -0400, Andrew Lutomirski wrote: > On Sun, May 15, 2011 at 11:27 AM, Wu Fengguang <fengguang.wu@xxxxxxxxx> wrote: > > On Sun, May 15, 2011 at 09:37:58AM +0800, Minchan Kim wrote: > >> On Sun, May 15, 2011 at 2:43 AM, Andi Kleen <andi@xxxxxxxxxxxxxx> wrote: > >> > Copying back linux-mm. > >> > > >> >> Recently, we added following patch. > >> >> https://lkml.org/lkml/2011/4/26/129 > >> >> If it's a culprit, the patch should solve the problem. > >> > > >> > It would be probably better to not do the allocations at all under > >> > memory pressure. ÂEven if the RA allocation doesn't go into reclaim > >> > >> Fair enough. > >> I think we can do it easily now. > >> If page_cache_alloc_readahead(ie, GFP_NORETRY) is fail, we can adjust > >> RA window size or turn off a while. The point is that we can use the > >> fail of __do_page_cache_readahead as sign of memory pressure. > >> Wu, What do you think? > > > > No, disabling readahead can hardly help. > > > > The sequential readahead memory consumption can be estimated by > > > > Â Â Â Â Â Â Â Â2 * (number of concurrent read streams) * (readahead window size) > > > > And you can double that when there are two level of readaheads. > > > > Since there are hardly any concurrent read streams in Andy's case, > > the readahead memory consumption will be ignorable. > > > > Typically readahead thrashing will happen long before excessive > > GFP_NORETRY failures, so the reasonable solutions are to > > > > - shrink readahead window on readahead thrashing > > Â(current readahead heuristic can somehow do this, and I have patches > > Âto further improve it) > > > > - prevent abnormal GFP_NORETRY failures > > Â(when there are many reclaimable pages) > > > > > > Andy's OOM memory dump (incorrect_oom_kill.txt.xz) shows that there are > > > > - 8MB Â active+inactive file pages > > - 160MB active+inactive anon pages > > - 1GB Â shmem pages > > - 1.4GB unevictable pages > > > > Hmm, why are there so many unevictable pages? ÂHow come the shmem > > pages become unevictable when there are plenty of swap space? > > That was probably because one of my testcases creates a 1.4GB file on > ramfs. (I can provoke the problem without doing evil things like > that, but the test script is rather reliable at killing my system and > it works fine on my other machines.) Ah I didn't read your first email.. I'm now running ./test_mempressure.sh 1500 1400 1 with mem=2G and no swap, but cannot reproduce OOM. What's your kconfig? > If you want, I can try to generate a trace that isn't polluted with > the evil ramfs file. 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; } Thanks, Fengguang -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>