linux-kernel - Re: [PATCH] x86_64: Make NR_IRQS configurable in Kconfig

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Date:	Tue, 8 Aug 2006 15:09:34 +1000
From:	Paul Mackerras <paulus@...ba.org>
To:	Andrew Morton <akpm@...l.org>
Cc:	Andi Kleen <ak@...e.de>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	"Randy.Dunlap" <rdunlap@...otime.net>,
	"Protasevich, Natalie" <Natalie.Protasevich@...sys.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86_64: Make NR_IRQS configurable in Kconfig

Andrew Morton writes:

> > Drawback would be some more TLB misses.
> 
> yup.  On some (important) architectures - I'm not sure which architectures
> do the bigpage-for-kernel trick.

I looked at optimizing the per-cpu data accessors on PowerPC and only
ever saw fractions of a percent change in overall performance, which
says to me that we don't actually use per-cpu data all that much.  So
unless you make per-cpu data really really slow, I doubt that we'll
see any significant performance difference.

Paul.
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