linux-kernel - Re: [PATCH] lib/cpumask.c: Optimize __any_online

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Message-ID: <4F3E45D2.5050100@linux.vnet.ibm.com>
Date:	Fri, 17 Feb 2012 17:49:30 +0530
From:	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
To:	Rusty Russell <rusty@...tcorp.com.au>
CC:	Eric Dumazet <eric.dumazet@...il.com>, akpm@...ux-foundation.org,
	kosaki.motohiro@...il.com, linux-kernel@...r.kernel.org,
	venki@...gle.com, Mike Travis <travis@....com>
Subject: Re: [PATCH] lib/cpumask.c: Optimize __any_online_cpu() calculation

On 02/16/2012 04:21 AM, Rusty Russell wrote:

> On Wed, 15 Feb 2012 19:49:00 +0530, "Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com> wrote:
>> On 02/15/2012 06:27 PM, Eric Dumazet wrote:
>>
>>> Le mercredi 15 février 2012 à 18:05 +0530, Srivatsa S. Bhat a écrit :
>>>> __any_online_cpu() uses a for loop at the moment.
>>>> Instead, use cpumask_* operations to speed it up.
>>>>
>>>> Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@...ux.vnet.ibm.com>
>>>> ---
>>>> Actually, the patch posted at https://lkml.org/lkml/2012/2/15/101 removed
>>>> the last user of any_online_cpu() (and hence __any_online_cpu()).
>>>> However, since this is an exported symbol, I refrained from removing this
>>>> function altogether.
>>>
>>> Just remove the export/function and eventually leave the helper ?
>>>
>>> #define any_online_cpu(mask) cpumask_any_and(mask, cpu_online_mask)
>>>
>>
>>
>> That sounds good. Here is v2 of the patch.
>> (Since this v2 touches include/linux/cpumask.h, I rebased it on top of the
>> patch posted at: https://lkml.org/lkml/2012/2/15/2. Even without that
>> patch it should apply with minor line number changes..)
> 
> No.  Just git rid of the only caller of any_online_cpu():
> 
> arch/ia64/kernel/smpboot.c:693:			new_cpei_cpu = any_online_cpu(cpu_online_map);
> 


My ia64 patch already got rid of that caller! So this patch should be fine as
is. And it looks like Andrew Morton has taken this patch into -mm. So nothing
more needs to be done about this :-)

Regards,
Srivatsa S. Bhat

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