linux-kernel - Re: [PATCHSET x86/core/percpu] improve the first percpu chunk allocation

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Message-ID: <49ADC80F.6010200@zytor.com>
Date:	Tue, 03 Mar 2009 16:15:11 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Rusty Russell <rusty@...tcorp.com.au>
CC:	Tejun Heo <tj@...nel.org>, Ingo Molnar <mingo@...e.hu>,
	tglx@...utronix.de, x86@...nel.org, linux-kernel@...r.kernel.org,
	jeremy@...p.org, cpw@....com, nickpiggin@...oo.com.au,
	ink@...assic.park.msu.ru
Subject: Re: [PATCHSET x86/core/percpu] improve the first percpu  chunk allocation

Rusty Russell wrote:
> On Wednesday 25 February 2009 01:07:24 Tejun Heo wrote:
>> it always
>> saves a 2MB TLB entry for all the non-NUMA machines out there.
> 
> Note that everyone keeps talking about "a" TLB entry; I wanted to make
> sure (esp. for those of us reading from the sidelines), it's not: it's
> up to num_possible_cpus() TLB entries.  Of course, many paths won't access
> other CPU's data, but it'd be interesting (and pretty easy) to actually
> instrument how rare this is...
> 

Actually it's up to the number of actual CPUs in the system... obviously 
there isn't any data allocated for non-present CPUs.

	-hpa
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