From: kashyap.desai@broadcom.com (Kashyap Desai)
Subject: [LSF/MM TOPIC] irq affinity handling for high CPU count machines
Date: Fri, 2 Feb 2018 14:19:01 +0530 [thread overview]
Message-ID: <6754a4c3ed7e1f1ea5473bd97625aa51@mail.gmail.com> (raw)
In-Reply-To: <20180202020235.GE19173@ming.t460p>
> > > > Today I am looking at one megaraid_sas related issue, and found
> > > > pci_alloc_irq_vectors(PCI_IRQ_AFFINITY) is used in the driver, so
> > > > looks each reply queue has been handled by more than one CPU if
> > > > there are more CPUs than MSIx vectors in the system, which is done
> > > > by generic irq affinity code, please see kernel/irq/affinity.c.
> >
> > Yes. That is a problematic area. If CPU and MSI-x(reply queue) is 1:1
> > mapped, we don't have any issue.
>
> I guess the problematic area is similar with the following link:
>
> https://marc.info/?l=linux-kernel&m=151748144730409&w=2
Hi Ming,
Above mentioned link is different discussion and looks like a generic
issue. megaraid_sas/mpt3sas will have same symptoms if irq affinity has
only offline CPUs.
Just for info - "In such condition, we can ask users to disable affinity
hit via module parameter " smp_affinity_enable".
>
> otherwise could you explain a bit about the area?
Please check below post for more details.
https://marc.info/?l=linux-scsi&m=151601833418346&w=2
next prev parent reply other threads:[~2018-02-02 8:49 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-29 9:08 [LSF/MM TOPIC] irq affinity handling for high CPU count machines Hannes Reinecke
2018-01-29 15:41 ` Elliott, Robert (Persistent Memory)
2018-01-29 16:37 ` Bart Van Assche
2018-01-29 16:42 ` Kashyap Desai
2018-02-01 15:05 ` Ming Lei
2018-02-01 16:20 ` Hannes Reinecke
2018-02-01 16:59 ` Kashyap Desai
2018-02-02 2:02 ` Ming Lei
2018-02-02 8:49 ` Kashyap Desai [this message]
2018-02-02 10:20 ` Ming Lei
2018-02-02 1:55 ` Ming Lei
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