Re: PATCH: softlockup: Fix hung_task_check_count sysctl

[AmÃrico Wang]

On Fri, Nov 27, 2009 at 10:28 AM, Anton Blanchard <anton@xxxxxxxxx> wrote:
>
> I'm seeing spikes of up to 0.5ms in khungtaskd on a large machine. To reduce
> this source of jitter I tried setting hung_task_check_count to 0:
>
> # echo 0 > /proc/sys/kernel/hung_task_check_count
>
> which didn't have the intended response. Change to a post increment of
> max_count, so a value of 0 means check 0 tasks.
>
> Signed-off-by: Anton Blanchard <anton@xxxxxxxxx>


Ack.

I would also suggest to make 'max_count' as unsigned long,
since sysctl_hung_task_check_count is.

Thanks.

> ---
>
> Index: linux.trees.git/kernel/hung_task.c
> ===================================================================
> --- linux.trees.git.orig/kernel/hung_task.c   2009-11-27 13:11:46.000000000 +1100
> +++ linux.trees.git/kernel/hung_task.c Â2009-11-27 13:11:57.000000000 +1100
> @@ -144,7 +144,7 @@ static void check_hung_uninterruptible_t
>
> Â Â Â Ârcu_read_lock();
> Â Â Â Âdo_each_thread(g, t) {
> - Â Â Â Â Â Â Â if (!--max_count)
> + Â Â Â Â Â Â Â if (!max_count--)
> Â Â Â Â Â Â Â Â Â Â Â Âgoto unlock;
> Â Â Â Â Â Â Â Âif (!--batch_count) {
> Â Â Â Â Â Â Â Â Â Â Â Âbatch_count = HUNG_TASK_BATCHING;
--
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