Messages in this thread | | | Date | Fri, 27 Nov 2009 03:55:13 +0100 | From | Frederic Weisbecker <> | Subject | Re: PATCH: softlockup: Fix hung_task_check_count sysctl |
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On Fri, Nov 27, 2009 at 10:46:53AM +0800, Américo Wang wrote: > On Fri, Nov 27, 2009 at 10:28 AM, Anton Blanchard <anton@samba.org> 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@samba.org> > > > Ack. > > I would also suggest to make 'max_count' as unsigned long, > since sysctl_hung_task_check_count is. > > Thanks.
Also, the batch_count thing should be dropped I think. This is a hardcoded, not overridable pause after 1024 threads checks to avoid latencies caused by rcu_read_lock. But now we have PREEMPT_RCU so people can enable it if they care about latency. We should remove it as it adds unnecessary complexity.
I'm preparing a patch for that, on top of Anton patch.
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