linux-kernel - Re: [patch] tlb flush_data: replace per

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Message-ID: <20090114090811.GQ23848@one.firstfloor.org>
Date:	Wed, 14 Jan 2009 10:08:11 +0100
From:	Andi Kleen <andi@...stfloor.org>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Ingo Molnar <mingo@...e.hu>,
	Ravikiran G Thirumalai <kiran@...lex86.org>,
	Frederik Deweerdt <frederik.deweerdt@...og.eu>,
	andi@...stfloor.org, tglx@...utronix.de, hpa@...or.com,
	linux-kernel@...r.kernel.org
Subject: Re: [patch] tlb flush_data: replace per_cpu with an array


> > It also would save some memory
> > on most distros out there (Ubuntu x86_64 has NR_CPUS=64 by default).

As pointed out several times this claim in the changelog is incorrect.
Please fix it.

A correct description would be:

- This patch wastes memory of one configured cache line for each CPU 
on systems with less than 8 cores (e.g. 896 bytes on a 1 core system
with CONFIG_GENERIC_CPU/ cache line size 128)
It saves some memory on systems with more than 8 cores (one cache
line size for each core above 8)

-Andi

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