Messages in this thread | | | Subject | Re: [PATCH RFC 1/1] genirq: Make threaded handler use irq affinity for managed interrupt | Date | Fri, 06 Dec 2019 15:22:53 +0000 | From | Marc Zyngier <> |
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Hi John,
On 2019-12-06 14:35, John Garry wrote: > Currently the cpu allowed mask for the threaded part of a threaded > irq > handler will be set to the effective affinity of the hard irq. > > Typically the effective affinity of the hard irq will be for a single > cpu. As such, > the threaded handler would always run on the same cpu as the hard > irq. > > We have seen scenarios in high data-rate throughput testing that the > cpu > handling the interrupt can be totally saturated handling both the > hard > interrupt and threaded handler parts, limiting throughput. > > For when the interrupt is managed, allow the threaded part to run on > all > cpus in the irq affinity mask. > > Signed-off-by: John Garry <john.garry@huawei.com> > --- > kernel/irq/manage.c | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > > diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c > index 1753486b440c..8e7f8e758a88 100644 > --- a/kernel/irq/manage.c > +++ b/kernel/irq/manage.c > @@ -968,7 +968,11 @@ irq_thread_check_affinity(struct irq_desc *desc, > struct irqaction *action) > if (cpumask_available(desc->irq_common_data.affinity)) { > const struct cpumask *m; > > - m = irq_data_get_effective_affinity_mask(&desc->irq_data); > + if (irqd_affinity_is_managed(&desc->irq_data)) > + m = desc->irq_common_data.affinity; > + else > + m = irq_data_get_effective_affinity_mask( > + &desc->irq_data); > cpumask_copy(mask, m); > } else { > valid = false;
Although I completely understand that there are cases where you really want to let your thread roam all CPUs, I feel like changing this based on a seemingly unrelated property is likely to trigger yet another whack-a-mole episode. I'd feel much more comfortable if there was a way to let the IRQ subsystem know about what is best.
Shouldn't the endpoint driver know better about it? Note that I have no data supporting an approach or the other, hence playing the role of the village idiot here.
Thanks,
M. -- Jazz is not dead. It just smells funny...
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