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Date: Fri, 19 Sep 2008 15:23:59 +0200
From: Eric Dumazet <dada1@cosmosbay.com>
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To: Christoph Lameter <cl@linux-foundation.org>
Cc: akpm@linux-foundation.org, linux-kernel@vger.kernel.org,
       Christoph Lameter <clameter@sgi.com>, linux-mm@vger.kernel.org,
       jeremy@goop.org, ebiederm@xmission.com, travis@sgi.com,
       herbert@gondor.apana.org.au, xemul@openvz.org
Subject: Re: [patch 4/4] cpu alloc: Use cpu allocator instead of the builtin
 modules per cpu allocator
References: <20080918233648.581696416@quilx.com> <20080918233701.832528677@quilx.com> <48D3574B.40209@cosmosbay.com> <48D3A22A.40508@linux-foundation.org>
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Christoph Lameter a écrit :
> Eric Dumazet wrote:
>> Christoph Lameter a écrit :
>>> Remove the builtin per cpu allocator from modules.c and use cpu_alloc
>>> instead.
>>>
>>> Signed-off-by: Christoph Lameter <clameter@sgi.com>
>>> +        percpu_size = sechdrs[pcpuindex].sh_size;
>>> +
>>> +        if (align > PAGE_SIZE) {
>>> +            printk(KERN_WARNING "%s: per-cpu alignment %li > %li\n",
>>> +                      mod->name, align, PAGE_SIZE);
>>> +            align = PAGE_SIZE;
>>> +        }
>> Minor question : Wy do you have to keep this cap of alignment ?
>>
>> I could not find such a limit in the allocator
> 
> The per cpu areas are allocated on page boundaries and there are multiple of
> those per cpu areas all aligned to page boundary. The alignment can therefore
> only make sense up to a page. Maybe I need to put that into the cpu allocator?

Ah... I missed this page boundaries on the allocator, you are right.

So caping is OK in modules code, in order to mimic previous behavior.

Adding an error case in cpu allocator (for align > PAGE_SIZE) might avoid some errors...