On 01/13/2017 05:35 AM, Ganapatrao Kulkarni wrote: > On Thu, Jan 12, 2017 at 4:40 PM, Vlastimil Babka <vbabka@xxxxxxx> wrote: >> On 01/11/2017 05:46 PM, Michal Hocko wrote: >>> >>> On Wed 11-01-17 21:52:29, Ganapatrao Kulkarni wrote: >>> >>>> [ 2398.169391] Node 1 Normal: 951*4kB (UME) 1308*8kB (UME) 1034*16kB >>>> (UME) 742*32kB (UME) 581*64kB (UME) 450*128kB (UME) 362*256kB (UME) >>>> 275*512kB (ME) 189*1024kB (UM) 117*2048kB (ME) 2742*4096kB (M) = 12047196kB >>> >>> >>> Most of the memblocks are marked Unmovable (except for the 4MB bloks) >> >> >> No, UME here means that e.g. 4kB blocks are available on unmovable, movable >> and reclaimable lists. >> >>> which shouldn't matter because we can fallback to unmovable blocks for >>> movable allocation AFAIR so we shouldn't really fail the request. I >>> really fail to see what is going on there but it smells really >>> suspicious. >> >> >> Perhaps there's something wrong with zonelists and we are skipping the Node >> 1 Normal zone. Or there's some race with cpuset operations (but can't see >> how). >> >> The question is, how reproducible is this? And what exactly the test >> cpuset01 does? Is it doing multiple things in a loop that could be reduced >> to a single testcase? > > IIUC, this test does node change to cpuset.mems in loop in parent > process in loop and child processes(equal to no of cpus) keeps on > allocation and freeing > 10 pages till the execution time is over. > more details at > https://github.com/linux-test-project/ltp/blob/master/testcases/kernel/mem/cpuset/cpuset01.c Ah, thanks for explaining. Looks like there might be a race where determining ac.preferred_zone using current_mems_allowed as ac.nodemask skips the only zone that is allowed after the cpuset.mems update, and we only recalculate ac.preferred_zone for allocations that are allowed to escape cpusets/watermarks. Thus we see only part of the zonelist, missing the only allowed zone. This would be due to commit 682a3385e773 ("mm, page_alloc: inline the fast path of the zonelist iterator") and/or some others from that series. Could you try with the following patch please? It also tries to protect from race with last non-root cpuset removal, which could cause cpusets_enable() to become false in the middle of the function. ----8<---- >From 9f041839401681f2678edf5040c851d11963c5fe Mon Sep 17 00:00:00 2001 From: Vlastimil Babka <vbabka@xxxxxxx> Date: Fri, 13 Jan 2017 10:01:26 +0100 Subject: [PATCH] mm, page_alloc: fix race with cpuset update or removal Changelog and S-O-B TBD. --- mm/page_alloc.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 6de9440e3ae2..c397f146843a 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -3775,9 +3775,17 @@ __alloc_pages_nodemask(gfp_t gfp_mask, unsigned int order, /* * Restore the original nodemask if it was potentially replaced with * &cpuset_current_mems_allowed to optimize the fast-path attempt. + * Also recalculate the starting point for the zonelist iterator or + * we could end up iterating over non-eligible zones endlessly. */ - if (cpusets_enabled()) + if (unlikely(ac.nodemask != nodemask)) { ac.nodemask = nodemask; + ac.preferred_zoneref = first_zones_zonelist(ac.zonelist, + ac.high_zoneidx, ac.nodemask); + if (!ac.preferred_zoneref) + goto no_zone; + } + page = __alloc_pages_slowpath(alloc_mask, order, &ac); no_zone: -- 2.11.0 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>