linux-kernel - Re: [PATCH V3] Fix Committed

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Date:	Mon, 20 Apr 2009 09:15:20 -0700
From:	Dave Hansen <dave@...ux.vnet.ibm.com>
To:	Eric B Munson <ebmunson@...ibm.com>
Cc:	kosaki.motohiro@...fujitsu.com, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, mel@...ux.vnet.ibm.com,
	cl@...ux-foundation.org
Subject: Re: [PATCH V3] Fix Committed_AS underflow

On Mon, 2009-04-20 at 10:09 +0100, Eric B Munson wrote:
> 1. Change NR_CPUS to min(64, NR_CPUS)
>    This will limit the amount of possible skew on kernels compiled for very
>    large SMP machines.  64 is an arbitrary number selected to limit the worst
>    of the skew without using more cache lines.  min(64, NR_CPUS) is used
>    instead of nr_online_cpus() because nr_online_cpus() requires a shared
>    cache line and a call to hweight to make the calculation.  Its runtime
>    overhead and keeping this counter accurate showed up in profiles and it's
>    possible that nr_online_cpus() would also show.



-- Dave

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