Messages in this thread | | | Date | Tue, 31 May 2011 09:13:47 +0600 | Subject | Re: [PATCH] mm, vmstat: Use cond_resched only when !CONFIG_PREEMPT | From | Rakib Mullick <> |
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On Tue, May 31, 2011 at 5:38 AM, KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> wrote: > On Mon, 30 May 2011 22:59:04 +0600 > Rakib Mullick <rakib.mullick@gmail.com> 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@gmail.com> > > 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 from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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