Messages in this thread Patch in this message | | | Date | Fri, 10 Jun 2011 09:38:42 -0700 | From | "Paul E. McKenney" <> | Subject | Re: [PATCH]rcu: avoid unnecessary thread wakeup |
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On Fri, Jun 10, 2011 at 03:50:51PM +0800, Shaohua Li wrote: > invoke_rcu_cpu_kthread could be called in the thread itself. In this case, > we don't need call wakeup, which is just wasting CPU. > > Signed-off-by: Shaohua Li <shaohua.li@intel.com> > > diff --git a/kernel/rcutree.c b/kernel/rcutree.c > index 89419ff..f9bd051 100644 > --- a/kernel/rcutree.c > +++ b/kernel/rcutree.c > @@ -1475,7 +1475,8 @@ static void invoke_rcu_cpu_kthread(void) > local_irq_restore(flags); > return; > } > - wake_up_process(__this_cpu_read(rcu_cpu_kthread_task)); > + if (current != __this_cpu_read(rcu_cpu_kthread_task)) > + wake_up_process(__this_cpu_read(rcu_cpu_kthread_task)); > local_irq_restore(flags); > }
Excellent point, thank you!
But how about combining the tests, perhaps something like the following?
Unless you have objections or spot problems with it (or it breaks during testing), I will queue the patch below with your SOB, since I derived it from your patch.
Thanx, Paul
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diff --git a/kernel/rcutree.c b/kernel/rcutree.c index b4b254d..eda3986 100644 --- a/kernel/rcutree.c +++ b/kernel/rcutree.c @@ -1523,11 +1523,9 @@ static void invoke_rcu_cpu_kthread(void) local_irq_save(flags); __this_cpu_write(rcu_cpu_has_work, 1); - if (__this_cpu_read(rcu_cpu_kthread_task) == NULL) { - local_irq_restore(flags); - return; - } - wake_up_process(__this_cpu_read(rcu_cpu_kthread_task)); + if (__this_cpu_read(rcu_cpu_kthread_task) != NULL && + current != __this_cpu_read(rcu_cpu_kthread_task)) + wake_up_process(__this_cpu_read(rcu_cpu_kthread_task)); local_irq_restore(flags); }
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