From: Marc Zyngier <maz@kernel.org>
To: Ming Lei <ming.lei@redhat.com>
Cc: John Garry <john.garry@huawei.com>, <tglx@linutronix.de>,
"chenxiang (M)" <chenxiang66@hisilicon.com>,
<bigeasy@linutronix.de>, <linux-kernel@vger.kernel.org>,
<hare@suse.com>, <hch@lst.de>, <axboe@kernel.dk>,
<bvanassche@acm.org>, <peterz@infradead.org>, <mingo@redhat.com>
Subject: Re: [PATCH RFC 1/1] genirq: Make threaded handler use irq affinity for managed interrupt
Date: Mon, 23 Dec 2019 09:07:39 +0000 [thread overview]
Message-ID: <fffcd23dd8286615b6e2c99620836cb1@www.loen.fr> (raw)
In-Reply-To: <20191220233138.GB12403@ming.t460p>
On 2019-12-20 23:31, Ming Lei wrote:
> On Fri, Dec 20, 2019 at 03:38:24PM +0000, John Garry wrote:
>> > > We've got some more results and it looks promising.
>> > >
>> > > So with your patch we get a performance boost of 3180.1K ->
>> 3294.9K
>> > > IOPS in the D06 SAS env. Then when we change the driver to use
>> > > threaded interrupt handler (mainline currently uses tasklet), we
>> get a
>> > > boost again up to 3415K IOPS.
>> > >
>> > > Now this is essentially the same figure we had with using
>> threaded
>> > > handler + the gen irq change in spreading the handler CPU
>> affinity. We
>> > > did also test your patch + gen irq change and got a performance
>> drop,
>> > > to 3347K IOPS.
>> > >
>> > > So tentatively I'd say your patch may be all we need.
>> >
>> > OK.
>> >
>> > > FYI, here is how the effective affinity is looking for both SAS
>> > > controllers with your patch:
>> > >
>> > > 74:02.0
>> > > irq 81, cpu list 24-29, effective list 24 cq
>> > > irq 82, cpu list 30-35, effective list 30 cq
>> >
>> > Cool.
>> >
>> > [...]
>> >
>> > > As for your patch itself, I'm still concerned of possible
>> regressions
>> > > if we don't apply this effective interrupt affinity spread
>> policy to
>> > > only managed interrupts.
>> >
>> > I'll try and revise that as I post the patch, probably at some
>> point
>> > between now and Christmas. I still think we should find a way to
>> > address this for the D05 SAS driver though, maybe by managing the
>> > affinity yourself in the driver. But this requires
>> experimentation.
>>
>> I've already done something experimental for the driver to manage
>> the
>> affinity, and performance is generally much better:
>>
>>
>> https://github.com/hisilicon/kernel-dev/commit/e15bd404ed1086fed44da34ed3bd37a8433688a7
>>
>> But I still think it's wise to only consider managed interrupts for
>> now.
>>
>> >
>> > > JFYI, about NVMe CPU lockup issue, there are 2 works on going
>> here:
>> > >
>> > >
>> https://lore.kernel.org/linux-nvme/20191209175622.1964-1-kbusch@kernel.org/T/#t
>> > >
>> > >
>> > >
>> https://lore.kernel.org/linux-block/20191218071942.22336-1-ming.lei@redhat.com/T/#t
>> > >
>> >
>> > I've also managed to trigger some of them now that I have access
>> to
>> > a decent box with nvme storage.
>>
>> I only have 2x NVMe SSDs when this occurs - I should not be hitting
>> this...
>>
>> Out of curiosity, have you tried
>> > with the SMMU disabled? I'm wondering whether we hit some livelock
>> > condition on unmapping buffers...
>>
>> No, but I can give it a try. Doing that should lower the CPU usage,
>> though,
>> so maybe masks the issue - probably not.
>
> Lots of CPU lockup can is performance issue if there isn't obvious
> bug.
>
> I am wondering if you may explain it a bit why enabling SMMU may save
> CPU a it?
The other way around. mapping/unmapping IOVAs doesn't comes for free.
I'm trying to find out whether the NVMe map/unmap patterns trigger
something unexpected in the SMMU driver, but that's a very long shot.
M.
--
Jazz is not dead. It just smells funny...
next prev parent reply other threads:[~2019-12-23 9:07 UTC|newest]
Thread overview: 57+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-06 14:35 [PATCH RFC 0/1] Threaded handler uses irq affinity for when the interrupt is managed John Garry
2019-12-06 14:35 ` [PATCH RFC 1/1] genirq: Make threaded handler use irq affinity for managed interrupt John Garry
2019-12-06 15:22 ` Marc Zyngier
2019-12-06 16:16 ` John Garry
2019-12-07 8:03 ` Ming Lei
2019-12-09 14:30 ` John Garry
2019-12-09 15:09 ` Hannes Reinecke
2019-12-09 15:17 ` Marc Zyngier
2019-12-09 15:25 ` Hannes Reinecke
2019-12-09 15:36 ` Marc Zyngier
2019-12-09 15:49 ` Qais Yousef
2019-12-09 15:55 ` Marc Zyngier
2019-12-10 1:43 ` Ming Lei
2019-12-10 9:45 ` John Garry
2019-12-10 10:06 ` Ming Lei
2019-12-10 10:28 ` Marc Zyngier
2019-12-10 10:59 ` John Garry
2019-12-10 11:36 ` Marc Zyngier
2019-12-10 12:05 ` John Garry
2019-12-10 18:32 ` Marc Zyngier
2019-12-11 9:41 ` John Garry
2019-12-13 10:07 ` John Garry
2019-12-13 10:31 ` Marc Zyngier
2019-12-13 12:08 ` John Garry
2019-12-14 10:59 ` Marc Zyngier
2019-12-11 17:09 ` John Garry
2019-12-12 22:38 ` Ming Lei
2019-12-13 11:12 ` John Garry
2019-12-13 13:18 ` Ming Lei
2019-12-13 15:43 ` John Garry
2019-12-13 17:12 ` Ming Lei
2019-12-13 17:50 ` John Garry
2019-12-14 13:56 ` Marc Zyngier
2019-12-16 10:47 ` John Garry
2019-12-16 11:40 ` Marc Zyngier
2019-12-16 14:17 ` John Garry
2019-12-16 18:00 ` Marc Zyngier
2019-12-16 18:50 ` John Garry
2019-12-20 11:30 ` John Garry
2019-12-20 14:43 ` Marc Zyngier
2019-12-20 15:38 ` John Garry
2019-12-20 16:16 ` Marc Zyngier
2019-12-20 23:31 ` Ming Lei
2019-12-23 9:07 ` Marc Zyngier [this message]
2019-12-23 10:26 ` John Garry
2019-12-23 10:47 ` Marc Zyngier
2019-12-23 11:35 ` John Garry
2019-12-24 1:59 ` Ming Lei
2019-12-24 11:20 ` Marc Zyngier
2019-12-25 0:48 ` Ming Lei
2020-01-02 10:35 ` John Garry
2020-01-03 0:46 ` Ming Lei
2020-01-03 10:41 ` John Garry
2020-01-03 11:29 ` Ming Lei
2020-01-03 11:50 ` John Garry
2020-01-04 12:03 ` Ming Lei
2020-05-30 7:46 ` [tip: irq/core] irqchip/gic-v3-its: Balance initial LPI affinity across CPUs tip-bot2 for Marc Zyngier
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