linux-kernel - Re: [RFC PATCH 1/2] mm, vmscan: account the number of isolated pages per zone

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Message-ID: <20170206103424.GC3097@dhcp22.suse.cz>
Date:   Mon, 6 Feb 2017 11:34:25 +0100
From:   Michal Hocko <mhocko@...nel.org>
To:     Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
Cc:     hch@....de, mgorman@...e.de, viro@...IV.linux.org.uk,
        linux-mm@...ck.org, hannes@...xchg.org,
        linux-kernel@...r.kernel.org, peterz@...radead.org
Subject: Re: [RFC PATCH 1/2] mm, vmscan: account the number of isolated pages
 per zone

On Sun 05-02-17 19:43:07, Tetsuo Handa wrote:
[...]
> Below one is also a loop. Maybe we can add __GFP_NOMEMALLOC to GFP_NOWAIT ?

No, GFP_NOWAIT is just too generic to use this flag.

> [  257.781715] Out of memory: Kill process 5171 (a.out) score 842 or sacrifice child
> [  257.784726] Killed process 5171 (a.out) total-vm:2177096kB, anon-rss:1476488kB, file-rss:4kB, shmem-rss:0kB
> [  257.787691] a.out(5171): TIF_MEMDIE allocation: order=0 mode=0x1000200(GFP_NOWAIT|__GFP_NOWARN)
> [  257.789789] CPU: 3 PID: 5171 Comm: a.out Not tainted 4.10.0-rc6-next-20170202+ #500
> [  257.791784] Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 07/02/2015
> [  257.794700] Call Trace:
> [  257.795690]  dump_stack+0x85/0xc9
> [  257.797224]  __alloc_pages_slowpath+0xacb/0xe36
> [  257.798612]  __alloc_pages_nodemask+0x382/0x3d0
> [  257.799942]  alloc_pages_current+0x97/0x1b0
> [  257.801236]  __get_free_pages+0x14/0x50
> [  257.802546]  __tlb_remove_page_size+0x70/0xd0

This is bound to MAX_GATHER_BATCH_COUNT which shouldn't be a lot of
pages (20 or so). We could add __GFP_NOMEMALLOC into tlb_next_batch
but I am not entirely convinced it is really necessary.
-- 
Michal Hocko
SUSE Labs