Re: [PATCH] mm: cache largest vma

From: Rik van Riel
Date: Fri Nov 01 2013 - 17:24:04 EST

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@xxxxxxxxxx>

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