linux-kernel - Re: [patch] mm, oom: stop reclaiming if GFP

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Date:   Mon, 27 Apr 2020 14:03:15 +0900
From:   Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
To:     David Rientjes <rientjes@...gle.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Vlastimil Babka <vbabka@...e.cz>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [patch] mm, oom: stop reclaiming if GFP_ATOMIC will start failing
 soon

On 2020/04/27 12:12, David Rientjes wrote:
> Tetsuo: the specific allocation that triggers a page allocation failure is 
> not interesting; we have tens of thousands of examples.  Each example is 
> simply the unlucky last GFP_ATOMIC allocation that fails; the interesting 
> point is the amount of free memory.  In other words, when free memory is 
> below ALLOC_HIGH watermarks, we assume that we have depleted memory 
> reserves *faster* than when user allocations started to fail.  In the 
> interest of userspace being responsive, we should oom kill here.

My interest is, which function (and which process if process context) is [ab]using
GFP_ATOMIC (or __GFP_MEMALLOC) allocations enough to hit memory allocation failure.
GFP_NOWAIT (or __GFP_NOMEMALLOC) could be used if that allocation can't sleep and
can't shortly recover free memory.