Messages in this thread | | | Date | Thu, 19 Dec 2013 14:03:47 -0500 | From | Prarit Bhargava <> | Subject | Re: [PATCH] x86: Add check for number of available vectors before CPU down |
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On 12/19/2013 02:19 AM, rui wang wrote: > On 12/19/13, Prarit Bhargava <prarit@redhat.com> wrote: >> >> >> On 12/03/2013 09:48 PM, rui wang wrote: >>> On 11/20/13, Prarit Bhargava <prarit@redhat.com> wrote: >>> Have you considered the case when an IRQ is destined to more than one CPU? >>> e.g.: >>> >>> bash# cat /proc/irq/89/smp_affinity_list >>> 30,62 >>> bash# >>> >>> In this case offlining CPU30 does not seem to require an empty vector >>> slot. It seems that we only need to change the affinity mask of irq89. >>> Your check_vectors() assumed that each irq on the offlining cpu >>> requires a new vector slot. >>> >> >> Rui, >> >> The smp_affinity_list only indicates a preferred destination of the IRQ, not >> the >> *actual* location of the CPU. So the IRQ is on one of cpu 30 or 62 but not >> both >> simultaneously. >> > > It depends on how IOAPIC (or MSI/MSIx) is configured. An IRQ can be > simultaneously broadcast to all destination CPUs (Fixed Mode) or > delivered to the CPU with the lowest priority task (Lowest Priority > Mode). It's programmed in the Delivery Mode bits of the IOAPIC's IO > Redirection table registers, or the Message Data Register in the case > of MSI/MSIx >
Thanks for clueing me in Rui :). You're right. I do need to do a
if (irq_has_action(irq) || !irqd_is_per_cpu(data) || !cpumask_subset(affinity, cpu_online_mask))
instead of just
if (!irqd_is_per_cpu(data))
I'm going to do some additional testing tonight across various systems and will repost tomorrow if the testing is successful.
P.
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