Re: [PATCH] mm, vmstat: Use cond_resched only when !CONFIG_PREEMPT

[KAMEZAWA Hiroyuki]

On Mon, 30 May 2011 22:59:04 +0600
Rakib Mullick <rakib.mullick@xxxxxxxxx> wrote:

> commit 468fd62ed9 (vmstats: add cond_resched() to refresh_cpu_vm_stats()) added cond_resched() in refresh_cpu_vm_stats. Purpose of that patch was to allow other threads to run in non-preemptive case. This patch, makes sure that cond_resched() gets called when !CONFIG_PREEMPT is set. In a preemptiable kernel we don't need to call cond_resched().
> 
> Signed-off-by: Rakib Mullick <rakib.mullick@xxxxxxxxx>

Hmm, what benefit do we get by adding this extra #ifdef in the code directly ?
Other cond_resched() callers are not guilty in !CONFIG_PREEMPT ?

Thanks,
-Kame

> ---
> 
> 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
> +
>  #ifdef CONFIG_NUMA
>  		/*
>  		 * Deal with draining the remote pageset of this
> 
> 

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