On Tue, May 31, 2011 at 5:38 AM, KAMEZAWA Hiroyuki
<kamezawa.hiroyu@xxxxxxxxxxxxxx> wrote:
> 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 ?
>
Well, in preemptible kernel this context will get preempted if
requires, so we don't need cond_resched(). If you checkout the git log
of the mentioned commit, you'll find the explanation. It says:
"Adding a cond_resched() to allow other threads to run in the
non-preemptive
case."
So, let cond_resched() be in non-preemptive case.
Thanks,
Rakib
> 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
>>
>>
>
>
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@xxxxxxxxxx For more info on Linux MM,
see: http://www.linux-mm.org/ .
Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/
Don't email: <a href