linux-kernel - Re: [PATCH 05/10] mm, page_alloc: Distinguish between being unable to sleep, unwilling to sleep and avoiding waking kswapd

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Message-ID: <20150924205509.GI3009@cmpxchg.org>
Date:	Thu, 24 Sep 2015 16:55:09 -0400
From:	Johannes Weiner <hannes@...xchg.org>
To:	Mel Gorman <mgorman@...hsingularity.net>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Rik van Riel <riel@...hat.com>,
	Vlastimil Babka <vbabka@...e.cz>,
	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 05/10] mm, page_alloc: Distinguish between being unable
 to sleep, unwilling to sleep and avoiding waking kswapd

On Mon, Sep 21, 2015 at 11:52:37AM +0100, Mel Gorman wrote:
> @@ -119,10 +134,10 @@ struct vm_area_struct;
>  #define GFP_USER	(__GFP_WAIT | __GFP_IO | __GFP_FS | __GFP_HARDWALL)
>  #define GFP_HIGHUSER	(GFP_USER | __GFP_HIGHMEM)
>  #define GFP_HIGHUSER_MOVABLE	(GFP_HIGHUSER | __GFP_MOVABLE)
> -#define GFP_IOFS	(__GFP_IO | __GFP_FS)
> -#define GFP_TRANSHUGE	(GFP_HIGHUSER_MOVABLE | __GFP_COMP | \
> -			 __GFP_NOMEMALLOC | __GFP_NORETRY | __GFP_NOWARN | \
> -			 __GFP_NO_KSWAPD)
> +#define GFP_IOFS	(__GFP_IO | __GFP_FS | __GFP_KSWAPD_RECLAIM)

These are some really odd semantics to be given a name like that.

GFP_IOFS was introduced as a short-hand for testing/setting/clearing
these two bits at the same time, not to be used for allocations. In
fact, the only user for allocations is lustre, and it's not at all
obious why those sites shouldn't include __GFP_WAIT as well.

Removing this definition altogether would probably be best.
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