From: Sagi Grimberg <sagi@grimberg.me>
To: Keith Busch <kbusch@kernel.org>
Cc: bigeasy@linutronix.de, ming.lei@redhat.com, tglx@linutronix.de,
linux-nvme@lists.infradead.org, hch@lst.de
Subject: Re: [PATCHv3 2/4] nvme/pci: Complete commands from primary handler
Date: Wed, 11 Dec 2019 16:40:47 -0800 [thread overview]
Message-ID: <79442e8d-719a-7510-deea-cc23694fdec0@grimberg.me> (raw)
In-Reply-To: <20191211173532.GB493@redsun51.ssa.fujisawa.hgst.com>
>>>> If I have say 24 (or more) devices with a queue mapped to a cpu, and we
>>>> happen to just reap in the primary handler for all devices, all the time,
>>>> are we safe from cpu lockup?
>>>
>>> I can't readily test that scenario, but I'm skeptical a workload
>>> can keep the primary handler running without ever seeing it return
>>> IRQ_WAKE_THREAD. If that is really a problem, we can mitigate it by
>>> limiting the number of CQEs the primary handler may process.
>>
>> Theoretically speaking, even if you limit to 1 cqe, the universe can
>> align such that you will always reap in the primary handler right?
>
> Perhaps theoretically, though testing the limits of reason.
I know, maybe we should handle it when/if this really becomes a
problem...
>> So if we have this optimization, perhaps something else in the irq
>> infrastructure should take care of cpu lockup prevention?
>
> Perhaps we can cycle the effective_affinity through the smp_affinity?
Not sure I follow your thoughts.
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next prev parent reply other threads:[~2019-12-12 0:40 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-09 17:56 [PATCHv3 0/4] nvme pci interrupt handling improvements Keith Busch
2019-12-09 17:56 ` [PATCHv3 1/4] nvme/pci: Disable interrupts for threaded handler Keith Busch
2019-12-10 15:12 ` Daniel Wagner
2019-12-10 15:28 ` Sebastian Andrzej Siewior
2019-12-10 15:54 ` Keith Busch
2019-12-10 16:44 ` Daniel Wagner
2019-12-10 16:57 ` Keith Busch
2019-12-10 17:11 ` Daniel Wagner
2019-12-12 9:09 ` Christoph Hellwig
2019-12-12 15:53 ` Keith Busch
2019-12-09 17:56 ` [PATCHv3 2/4] nvme/pci: Complete commands from primary handler Keith Busch
2019-12-10 20:00 ` Sagi Grimberg
2019-12-10 20:25 ` Keith Busch
2019-12-10 21:14 ` Sagi Grimberg
2019-12-11 17:35 ` Keith Busch
2019-12-12 0:40 ` Sagi Grimberg [this message]
2019-12-12 1:02 ` Keith Busch
2019-12-12 22:55 ` Ming Lei
2019-12-12 23:30 ` Keith Busch
2019-12-13 0:52 ` Ming Lei
2019-12-12 9:14 ` Christoph Hellwig
2019-12-09 17:56 ` [PATCHv3 3/4] nvme/pci: Remove use_threaded_interrupts Keith Busch
2019-12-12 9:14 ` Christoph Hellwig
2019-12-12 15:45 ` Keith Busch
2019-12-18 7:29 ` Ming Lei
2019-12-18 15:50 ` Keith Busch
2019-12-19 1:10 ` Ming Lei
2019-12-09 17:56 ` [PATCHv3 4/4] nvme/pci: Poll threaded completions Keith Busch
2019-12-10 17:43 ` Daniel Wagner
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