linux-kernel - Re: [PATCH 07/12] mm, page_alloc: Distinguish between being unable to sleep, unwilling to sleep and avoiding waking kswapd

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Date:	Thu, 27 Aug 2015 11:18:17 +0200
From:	Vlastimil Babka <vbabka@...e.cz>
To:	Mel Gorman <mgorman@...hsingularity.net>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Johannes Weiner <hannes@...xchg.org>,
	Rik van Riel <riel@...hat.com>,
	David Rientjes <rientjes@...gle.com>,
	Joonsoo Kim <iamjoonsoo.kim@....com>,
	Michal Hocko <mhocko@...nel.org>,
	Linux-MM <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 07/12] mm, page_alloc: Distinguish between being unable to
 sleep, unwilling to sleep and avoiding waking kswapd

On 08/26/2015 08:10 PM, Mel Gorman wrote:
>>
>> I think the most robust check would be to rely on what was already prepared
>> by gfp_to_alloc_flags(), instead of repeating it here. So add alloc_flags
>> parameter to warn_alloc_failed(), and drop the filter when
>> - ALLOC_CPUSET is not set, as that disables the cpuset checks
>> - ALLOC_NO_WATERMARKS is set, as that allows calling
>>    __alloc_pages_high_priority() attempt which ignores cpusets
>>
>
> warn_alloc_failed is used outside of page_alloc.c in a context that does
> not have alloc_flags. It could be extended to take an extra parameter
> that is ALLOC_CPUSET for the other callers or else split it into
> __warn_alloc_failed (takes alloc_flags parameter) and warn_alloc_failed
> (calls __warn_alloc_failed with ALLOC_CPUSET) but is it really worth it?

Probably not. Testing lack of __GFP_DIRECT_RECLAIM is good enough until 
somebody cares more.
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