linux-kernel - Re: [PATCH] mm: cache largest vma

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Date:	Fri, 01 Nov 2013 17:23:44 -0400
From:	Rik van Riel <riel@...hat.com>
To:	Davidlohr Bueso <davidlohr@...com>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	Hugh Dickins <hughd@...gle.com>,
	Michel Lespinasse <walken@...gle.com>,
	Ingo Molnar <mingo@...nel.org>, Mel Gorman <mgorman@...e.de>,
	Guan Xuetao <gxt@...c.pku.edu.cn>, aswin@...com,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH] mm: cache largest vma

On 11/01/2013 04:17 PM, Davidlohr Bueso wrote:
> While caching the last used vma already does a nice job avoiding
> having to iterate the rbtree in find_vma, we can improve. After
> studying the hit rate on a load of workloads and environments,
> it was seen that it was around 45-50% - constant for a standard
> desktop system (gnome3 + evolution + firefox + a few xterms),
> and multiple java related workloads (including Hadoop/terasort),
> and aim7, which indicates it's better than the 35% value documented
> in the code.
> 
> By also caching the largest vma, that is, the one that contains
> most addresses, there is a steady 10-15% hit rate gain, putting
> it above the 60% region. This improvement comes at a very low

I suspect this will especially help when also using automatic
numa balancing, which causes periodic page faults.

Acked-by: Rik van Riel <riel@...hat.com>

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