linux-kernel - Re: [PATCH 03/10] mm, page_alloc: Remove unnecessary recalculations for dirty zone balancing

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Message-ID: <20150820134526.GD12432@techsingularity.net>
Date:	Thu, 20 Aug 2015 14:45:26 +0100
From:	Mel Gorman <mgorman@...hsingularity.net>
To:	Michal Hocko <mhocko@...nel.org>
Cc:	Linux-MM <linux-mm@...ck.org>,
	Johannes Weiner <hannes@...xchg.org>,
	Rik van Riel <riel@...hat.com>,
	Vlastimil Babka <vbabka@...e.cz>,
	David Rientjes <rientjes@...gle.com>,
	Joonsoo Kim <iamjoonsoo.kim@....com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 03/10] mm, page_alloc: Remove unnecessary recalculations
 for dirty zone balancing

On Thu, Aug 20, 2015 at 02:45:27PM +0200, Michal Hocko wrote:
> On Wed 12-08-15 11:45:28, Mel Gorman wrote:
> > File-backed pages that will be immediately are balanced between zones but
> 					    ^written to...
> 
> > it's unnecessarily expensive.
> 
> to do WHAT? I guess you meant checking gfp_mask resp. alloc_mask? I
> doubt it would make a noticeable difference as this is a slow path
> already but I agree it doesn't make sense to check it again.
> 

File-backed pages that will be immediately written are balanced between
zones.  This heuristic tries to avoid having a single zone filled with
recently dirtied pages but the checks are unnecessarily expensive. Move
consider_zone_balanced into the alloc_context instead of checking bitmaps
multiple times. The patch also gives the parameter a more meaningful name.

?

-- 
Mel Gorman
SUSE Labs
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