linux-kernel - Re: [PATCH 2/6] change alloc function in pcpu_alloc

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Message-ID: <v2j28c262361004141831h8f2110d5pa7a1e3063438cbf8@mail.gmail.com>
Date:	Thu, 15 Apr 2010 10:31:23 +0900
From:	Minchan Kim <minchan.kim@...il.com>
To:	Tejun Heo <tj@...nel.org>
Cc:	Mel Gorman <mel@....ul.ie>,
	Andrew Morton <akpm@...ux-foundation.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Bob Liu <lliubbo@...il.com>, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org, Christoph Lameter <cl@...ux-foundation.org>
Subject: Re: [PATCH 2/6] change alloc function in pcpu_alloc_pages

Hi, Tejun.

On Thu, Apr 15, 2010 at 8:39 AM, Tejun Heo <tj@...nel.org> wrote:
> Hello,
>
> On 04/14/2010 12:48 AM, Mel Gorman wrote:
>> and the mapping table on x86 at least is based on possible CPUs in
>> init_cpu_to_node() leaves the mapping as 0 if the APIC is bad or the numa
>> node is reported in apicid_to_node as -1. It would appear on power that
>> the node will be 0 for possible CPUs as well.
>>
>> Hence, I believe this to be safe but a confirmation from Tejun would be
>> nice. I would continue digging but this looks like an initialisation path
>> so I'll move on to the next patch rather than spending more time.
>
> This being a pretty cold path, I don't really see much benefit in
> converting it to alloc_pages_node_exact().  It ain't gonna make any
> difference.  I'd rather stay with the safer / boring one unless
> there's a pressing reason to convert.

Actually, It's to weed out not-good API usage as well as some performance gain.
But I don't think to need it strongly.
Okay. Please keep in mind about this and correct it if you confirms it
in future. :)

>
> Thanks.
>
> --
> tejun
>



-- 
Kind regards,
Minchan Kim
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