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    SubjectRe: PATCH: softlockup: Fix hung_task_check_count sysctl
    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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