linux-kernel - Re: [PATCH 2/2] Allow percpu variables to be page-aligned

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Message-ID: <461C1470.60308@goop.org>
Date:	Tue, 10 Apr 2007 15:49:20 -0700
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
CC:	Andrew Morton <akpm@...ux-foundation.org>, Andi Kleen <ak@...e.de>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Rusty Russell <rusty@...tcorp.com.au>
Subject: Re: [PATCH 2/2] Allow percpu variables to be page-aligned

Eric W. Biederman wrote:
> Jeremy Fitzhardinge <jeremy@...p.org> writes:
>
>   
>> Let's allow page-alignment in general for per-cpu data (wanted by Xen, and
>> Ingo suggested KVM as well).
>>
>> Because larger alignments can use more room, we increase the max per-cpu
>> memory to 64k rather than 32k: it's getting a little tight.
>>     
>
> The second paragraph of the comment is dated.  You are not changing the per-cpu 
> memory size at all now.
>   

Yup.

> Although we should probably fail the module load if the requested alignment
> is to great, but that is just picking nits, and is no worse than what we
> do today.
>   

Yes.  And we barely support a module's use of page-aligned data, since
it would potentially chew through the percpu space very quickly.

    J
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