Messages in this thread | | | Subject | Re: [PATCH RFC] irq: Set CPU affinity as soon as the irq thread is created | From | Steven Rostedt <> | Date | Wed, 05 Sep 2012 20:09:15 -0400 |
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On Wed, 2012-09-05 at 18:07 -0500, Sankara Muthukrishnan wrote: > Hi there,
This also affects mainline. Please Cc LKML (as I did).
> > As irq_thread_check_affinity is called inside the while loop in the > IRQ thread, the core affinity is set only when an interrupt happens. > It does not seem to be a bad idea to set the core affinity soon after > the thread is created also (as shown in the patch). > irq_thread_check_affinity calls kmalloc_node that can sleep.
Note, it only calls kmalloc if you enable CONFIG_CPUMASK_OFFSTACK, which you probably don't on an embedded device. But you might. Your embedded device may have more than 32 or 64 CPUs.
I'd be more worried about calling set_cpus_allowed_ptr() than kmalloc().
> In an > embedded target where IRQ affinities are pre-configured during > boot-time (and not modified through /proc/irq/../smp_affinity) during > run-time, the extra latency due to irq_thread_check_affinity can be > avoided during processing of the first interrupt with this patch. > Thoughts? > > diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c > index 87dc053..bf2cdc2 100644 > --- a/kernel/irq/manage.c > +++ b/kernel/irq/manage.c > @@ -791,6 +791,7 @@ static int irq_thread(void *data) > > sched_setscheduler(current, SCHED_FIFO, ¶m); > current->irqaction = action; > + irq_thread_check_affinity(desc, action); > > while (!irq_wait_for_interrupt(action)) {
I see no problem with this patch.
Acked-by: Steven Rostedt <rostedt@goodmis.org>
-- Steve
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