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Date: Sun, 8 Sep 2002 21:48:58 +0100 (BST)
From: Hugh Dickins <hugh@veritas.com>
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To: Andrew Morton <akpm@digeo.com>
cc: Alan Cox <alan@lxorguk.ukuu.org.uk>,
       "Martin J. Bligh" <Martin.Bligh@us.ibm.com>,
       William Lee Irwin III <wli@holomorphy.com>,
       Paolo Ciarrocchi <ciarrocchi@linuxmail.org>,
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Subject: Re: LMbench2.0 results
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On Sun, 8 Sep 2002, Andrew Morton wrote:
> 
> We need to find some way of making vm_enough_memory not call get_page_state
> so often.  One way of doing that might be to make get_page_state dump
> its latest result into a global copy, and make vm_enough_memory()
> only get_page_state once per N invokations.  A speed/accuracy tradeoff there.

Accuracy is not very important in that sysctl_overcommit_memory 0 case
e.g. the swapper_space.nr_pages addition was brought in at a time when
it was very necessary, but usually overestimates now (or last time I
thought about it).  The main thing to look out for is running the same
memory grabber twice in quick succession: not nice if it succeeds the
first time, but not the second, just because of some transient effect
that its old pages are temporarily uncounted.

Hugh

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