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: <20150925190138.GA16359@cmpxchg.org>
Date:	Fri, 25 Sep 2015 15:01:38 -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 Fri, Sep 25, 2015 at 01:51:06PM +0100, Mel Gorman wrote:
> On Thu, Sep 24, 2015 at 04:55:09PM -0400, Johannes Weiner wrote:
> > 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.
> 
> Ok, I'll add a TODO to create a patch that removes GFP_IOFS entirely. It
> can be tacked on to the end of the series.

Okay, that makes sense to me. Thanks!

Acked-by: Johannes Weiner <hannes@...xchg.org>
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