Messages in this thread | | | Date | Mon, 23 Dec 2019 14:18:51 -0500 | From | Peter Xu <> | Subject | Re: Kernel-managed IRQ affinity (cont) |
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On Thu, Dec 19, 2019 at 01:09:17PM -0500, Peter Xu wrote: > On Fri, Dec 20, 2019 at 12:11:15AM +0800, Ming Lei wrote: > > OK, please try the following patch: > > > > > > diff --git a/include/linux/sched/isolation.h b/include/linux/sched/isolation.h > > index 6c8512d3be88..0fbcbacd1b29 100644 > > --- a/include/linux/sched/isolation.h > > +++ b/include/linux/sched/isolation.h > > @@ -13,6 +13,7 @@ enum hk_flags { > > HK_FLAG_TICK = (1 << 4), > > HK_FLAG_DOMAIN = (1 << 5), > > HK_FLAG_WQ = (1 << 6), > > + HK_FLAG_MANAGED_IRQ = (1 << 7), > > }; > > > > #ifdef CONFIG_CPU_ISOLATION > > diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c > > index 1753486b440c..0a75a09cc4e8 100644 > > --- a/kernel/irq/manage.c > > +++ b/kernel/irq/manage.c > > @@ -20,6 +20,7 @@ > > #include <linux/sched/task.h> > > #include <uapi/linux/sched/types.h> > > #include <linux/task_work.h> > > +#include <linux/sched/isolation.h> > > > > #include "internals.h" > > > > @@ -212,12 +213,33 @@ int irq_do_set_affinity(struct irq_data *data, const struct cpumask *mask, > > { > > struct irq_desc *desc = irq_data_to_desc(data); > > struct irq_chip *chip = irq_data_get_irq_chip(data); > > + const struct cpumask *housekeeping_mask = > > + housekeeping_cpumask(HK_FLAG_MANAGED_IRQ); > > int ret; > > + cpumask_var_t tmp_mask; > > > > if (!chip || !chip->irq_set_affinity) > > return -EINVAL; > > > > - ret = chip->irq_set_affinity(data, mask, force); > > + if (!zalloc_cpumask_var(&tmp_mask, GFP_KERNEL)) > > + return -EINVAL; > > + > > + /* > > + * Userspace can't change managed irq's affinity, make sure > > + * that isolated CPU won't be selected as the effective CPU > > + * if this irq's affinity includes both isolated CPU and > > + * housekeeping CPU. > > + * > > + * This way guarantees that isolated CPU won't be interrupted > > + * by IO submitted from housekeeping CPU. > > + */ > > + if (irqd_affinity_is_managed(data) && > > + cpumask_intersects(mask, housekeeping_mask)) > > + cpumask_and(tmp_mask, mask, housekeeping_mask); > > + else > > + cpumask_copy(tmp_mask, mask); > > + > > + ret = chip->irq_set_affinity(data, tmp_mask, force); > > switch (ret) { > > case IRQ_SET_MASK_OK: > > case IRQ_SET_MASK_OK_DONE: > > @@ -229,6 +251,8 @@ int irq_do_set_affinity(struct irq_data *data, const struct cpumask *mask, > > ret = 0; > > } > > > > + free_cpumask_var(tmp_mask); > > + > > return ret; > > } > > > > diff --git a/kernel/sched/isolation.c b/kernel/sched/isolation.c > > index 9fcb2a695a41..008d6ac2342b 100644 > > --- a/kernel/sched/isolation.c > > +++ b/kernel/sched/isolation.c > > @@ -163,6 +163,12 @@ static int __init housekeeping_isolcpus_setup(char *str) > > continue; > > } > > > > + if (!strncmp(str, "managed_irq,", 12)) { > > + str += 12; > > + flags |= HK_FLAG_MANAGED_IRQ; > > + continue; > > + } > > + > > pr_warn("isolcpus: Error, unknown flag\n"); > > return 0; > > } > > Thanks for the quick patch. I'll test after my current round of tests > finish and update. I'll probably believe this will work for us as > long as it "functionally" works :) (after all it won't even need a RT > environment because it's really about where to put some IRQs). So > IMHO the more important thing is whether such a solution could be > acceptable by the upstream.
I've tested this patch, it works for us. "isolcpus=managed_irq,2-9" gives me:
[root@rt-vm 32]# pwd /proc/irq/32 [root@rt-vm 32]# cat smp_affinity 003 [root@rt-vm 32]# cat effective_affinity 001
Thomas, do you think Ming's solution could be accepted?
Thanks,
-- Peter Xu
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