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Subject: Re: [patch] mm, oom: stop reclaiming if GFP_ATOMIC will start failing
 soon
To:     David Rientjes <rientjes@google.com>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        Vlastimil Babka <vbabka@suse.cz>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org
References: <alpine.DEB.2.22.394.2004241347310.70176@chino.kir.corp.google.com>
 <20200425172706.26b5011293e8dc77b1dccaf3@linux-foundation.org>
 <alpine.DEB.2.22.394.2004261959310.80211@chino.kir.corp.google.com>
From:   Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Message-ID: <fed6a727-1005-cb12-0ad0-4d9a6bb06564@I-love.SAKURA.ne.jp>
Date:   Mon, 27 Apr 2020 14:03:15 +0900
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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.