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Message-ID: <20160524071619.GB8259@dhcp22.suse.cz> Date: Tue, 24 May 2016 09:16:19 +0200 From: Michal Hocko <mhocko@...nel.org> To: Oleg Nesterov <oleg@...hat.com> Cc: Andrew Morton <akpm@...ux-foundation.org>, Andrea Arcangeli <aarcange@...hat.com>, Mel Gorman <mgorman@...hsingularity.net>, linux-kernel@...r.kernel.org, linux-mm@...ck.org Subject: Re: zone_reclaimable() leads to livelock in __alloc_pages_slowpath() On Mon 23-05-16 17:14:19, Oleg Nesterov wrote: > On 05/23, Michal Hocko wrote: [...] > > Could you add some tracing and see what are the numbers > > above? > > with the patch below I can press Ctrl-C when it hangs, this breaks the > endless loop and the output looks like > > vmscan: ZONE=ffffffff8189f180 0 scanned=0 pages=6 > vmscan: ZONE=ffffffff8189eb00 0 scanned=1 pages=0 > ... > vmscan: ZONE=ffffffff8189eb00 0 scanned=2 pages=1 > vmscan: ZONE=ffffffff8189f180 0 scanned=4 pages=6 > ... > vmscan: ZONE=ffffffff8189f180 0 scanned=4 pages=6 > vmscan: ZONE=ffffffff8189f180 0 scanned=4 pages=6 > > the numbers are always small. Small but scanned is not 0 and constant which means it either gets reset repeatedly (something gets freed) or we have stopped scanning. Which pattern can you see? I assume that the swap space is full at the time (could you add get_nr_swap_pages() to the output). Also zone->name would be better than the pointer. I am trying to reproduce but your test case always hits the oom killer: This is in a qemu x86_64 virtual machine: # free total used free shared buffers cached Mem: 490212 96788 393424 0 3196 9976 -/+ buffers/cache: 83616 406596 Swap: 138236 57740 80496 I have tried with much larger swap space but no change except for the run time of the test which is expected. # grep "^processor" /proc/cpuinfo | wc -l 1 [... Skipped several previous attempts ...] [ 695.215235] vmscan: XXX: zone:DMA32 nr_pages_scanned:0 reclaimable:20 [ 695.215245] vmscan: XXX: zone:DMA32 nr_pages_scanned:0 reclaimable:20 [ 695.215255] vmscan: XXX: zone:DMA32 nr_pages_scanned:0 reclaimable:20 [ 695.215282] vmscan: XXX: zone:DMA32 nr_pages_scanned:1 reclaimable:27 [ 695.215303] vmscan: XXX: zone:DMA32 nr_pages_scanned:5 reclaimable:27 [ 695.215327] vmscan: XXX: zone:DMA32 nr_pages_scanned:18 reclaimable:27 [ 695.215351] vmscan: XXX: zone:DMA32 nr_pages_scanned:45 reclaimable:27 [ 695.215362] vmscan: XXX: zone:DMA32 nr_pages_scanned:45 reclaimable:27 [ 695.215373] vmscan: XXX: zone:DMA32 nr_pages_scanned:45 reclaimable:27 [ 695.215382] vmscan: XXX: zone:DMA32 nr_pages_scanned:45 reclaimable:27 [ 695.215392] vmscan: XXX: zone:DMA32 nr_pages_scanned:45 reclaimable:27 [ 695.215402] vmscan: XXX: zone:DMA32 nr_pages_scanned:45 reclaimable:27 [ 695.215412] vmscan: XXX: zone:DMA32 nr_pages_scanned:45 reclaimable:27 [ 695.215422] vmscan: XXX: zone:DMA32 nr_pages_scanned:45 reclaimable:27 [ 695.215431] vmscan: XXX: zone:DMA32 nr_pages_scanned:45 reclaimable:27 [ 695.215442] vmscan: XXX: zone:DMA32 nr_pages_scanned:46 reclaimable:27 [ 695.215462] vmscan: XXX: zone:DMA32 nr_pages_scanned:48 reclaimable:27 [ 695.215482] vmscan: XXX: zone:DMA32 nr_pages_scanned:53 reclaimable:27 [ 695.215504] vmscan: XXX: zone:DMA32 nr_pages_scanned:63 reclaimable:27 [ 695.215528] vmscan: XXX: zone:DMA32 nr_pages_scanned:90 reclaimable:27 [...] [ 695.215620] vmscan: XXX: zone:DMA32 nr_pages_scanned:91 reclaimable:27 [ 695.215640] vmscan: XXX: zone:DMA32 nr_pages_scanned:94 reclaimable:27 [ 695.215659] vmscan: XXX: zone:DMA32 nr_pages_scanned:100 reclaimable:27 [ 695.215683] vmscan: XXX: zone:DMA32 nr_pages_scanned:113 reclaimable:27 [...] [ 695.215786] vmscan: XXX: zone:DMA32 nr_pages_scanned:140 reclaimable:27 [ 695.215797] vmscan: XXX: zone:DMA32 nr_pages_scanned:141 reclaimable:27 [ 695.215816] vmscan: XXX: zone:DMA32 nr_pages_scanned:144 reclaimable:27 [ 695.215836] vmscan: XXX: zone:DMA32 nr_pages_scanned:150 reclaimable:27 [ 695.215906] test-oleg invoked oom-killer: gfp_mask=0x24201ca(GFP_HIGHUSER_MOVABLE|__GFP_COLD), order=0, oom_score_adj=0 -- Michal Hocko SUSE Labs
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