Re: [PATCH RFC] irq: Set CPU affinity as soon as the irq thread is created
From: Steven Rostedt <rostedt@goodmis.org>
Date: 2012-09-06 00:09:19
Also in:
lkml
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().
quoted hunk ↗ jump to hunk
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