linux-kernel - Re: [patch 3/3] mm: page_alloc: fair zone allocator policy

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Message-ID: <20130725151049.GM715@cmpxchg.org>
Date:	Thu, 25 Jul 2013 11:10:49 -0400
From:	Johannes Weiner <hannes@...xchg.org>
To:	Paul Bolle <paul.bollee@...il.com>
Cc:	Rik van Riel <riel@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Mel Gorman <mgorman@...e.de>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Paul Bolle <pebolle@...cali.nl>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [patch 3/3] mm: page_alloc: fair zone allocator policy

Hi Paul Bolle^W^W Sam Ben^W^W Hush Bensen^W^W Mtrr Patt^W^W Ric
Mason^W^W Will Huck^W^W Simon Jeons^W^W Jaeguk Hanse^W^W Ni zhan
Chen^W^W^W Wanpeng Li

[ I Cc'd Paul Bolle at pebolle@...cali.nl as well, his English was
  better from there ]

On Thu, Jul 25, 2013 at 02:50:54PM +0800, Paul Bolle wrote:
> On 07/23/2013 04:21 AM, Rik van Riel wrote:
> >On 07/19/2013 04:55 PM, Johannes Weiner wrote:
> >
> >>@@ -1984,7 +1992,8 @@ this_zone_full:
> >>          goto zonelist_scan;
> >>      }
> >>
> >>-    if (page)
> >>+    if (page) {
> >>+        atomic_sub(1U << order, &zone->alloc_batch);
> >>          /*
> >>           * page->pfmemalloc is set when ALLOC_NO_WATERMARKS was
> >>           * necessary to allocate the page. The expectation is
> >
> >Could this be moved into the slow path in buffered_rmqueue and
> >rmqueue_bulk, or would the effect of ignoring the pcp buffers be
> >too detrimental to keeping the balance between zones?
> >
> >It would be kind of nice to not have this atomic operation on every
> >page allocation...
> 
> atomic operation will lock cache line or memory bus? And cmpxchg
> will lock cache line or memory bus? ;-)

Sure, why not ;-)
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