linux-kernel - Re: [PATCH] mm, vmstat: Use cond_resched only when !CONFIG

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Date:	Tue, 31 May 2011 09:19:03 +0600
From:	Rakib Mullick <rakib.mullick@...il.com>
To:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
Cc:	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	akpm@...ux-foundation.org, cl@...ux.com,
	kamezawa.hiroyu@...fujitsu.com, mel@....ul.ie
Subject: Re: [PATCH] mm, vmstat: Use cond_resched only when !CONFIG_PREEMPT

On Tue, May 31, 2011 at 8:23 AM, KOSAKI Motohiro
<kosaki.motohiro@...fujitsu.com> wrote:
>> diff --git a/mm/vmstat.c b/mm/vmstat.c
>> index 20c18b7..72cf857 100644
>> --- a/mm/vmstat.c
>> +++ b/mm/vmstat.c
>> @@ -461,7 +461,11 @@ void refresh_cpu_vm_stats(int cpu)
>>                               p->expire = 3;
>>  #endif
>>                       }
>> +
>> +#ifndef CONFIG_PREEMPT
>>               cond_resched();
>> +#endif
>> +
>
> In general, we should avoid #ifdef CONFIG_PREEMPT for maintainancebility as far as possible.
> Is there any observable benefit? Can you please demonstrate it?
>
On my system I'm not sure whether it shows demonstratable benefit or
not. Although, I try. It will be helpful if you give me a hint about
how to measure its benefit.

Thanks,
Rakib
>
>
>
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