linux-kernel - Re: [PATCH RFC 1/1] genirq: Make threaded handler use irq affinity for managed interrupt

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Date:   Sat, 14 Dec 2019 13:56:41 +0000
From:   Marc Zyngier <maz@...nel.org>
To:     John Garry <john.garry@...wei.com>
Cc:     Ming Lei <ming.lei@...hat.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "chenxiang (M)" <chenxiang66@...ilicon.com>,
        "bigeasy@...utronix.de" <bigeasy@...utronix.de>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "hare@...e.com" <hare@...e.com>, "hch@....de" <hch@....de>,
        "axboe@...nel.dk" <axboe@...nel.dk>,
        "bvanassche@....org" <bvanassche@....org>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "mingo@...hat.com" <mingo@...hat.com>
Subject: Re: [PATCH RFC 1/1] genirq: Make threaded handler use irq affinity
 for managed interrupt

On Fri, 13 Dec 2019 15:43:07 +0000
John Garry <john.garry@...wei.com> wrote:

[...]

> john@...ntu:~$ ./dump-io-irq-affinity
> kernel version:
> Linux ubuntu 5.5.0-rc1-00003-g7adc5d7ec1ca-dirty #1440 SMP PREEMPT Fri Dec 13 14:53:19 GMT 2019 aarch64 aarch64 aarch64 GNU/Linux
> PCI name is 04:00.0: nvme0n1
> irq 56, cpu list 75, effective list 5
> irq 60, cpu list 24-28, effective list 10

The NUMA selection code definitely gets in the way. And to be honest,
this NUMA thing is only there for the benefit of a terminally broken
implementation (Cavium ThunderX), which we should have never supported
the first place.

Let's rework this and simply use the managed affinity whenever
available instead. It may well be that it will break TX1, but I care
about it just as much as Cavium/Marvell does...

Please give this new patch a shot on your system (my D05 doesn't have
any managed devices):

https://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms.git/commit/?h=irq/its-balance-mappings&id=1e987d83b8d880d56c9a2d8a86289631da94e55a

Thanks,

	M.

-- 
Jazz is not dead. It just smells funny...