linux-kernel - Re: [PATCH] genirq/proc: Show percpu irq affinity

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Date:   Sat, 22 Aug 2020 13:35:10 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Yunfeng Ye <yeyunfeng@...wei.com>
Cc:     linux-kernel@...r.kernel.org, Shiyuan Hu <hushiyuan@...wei.com>,
        Hewenliang <hewenliang4@...wei.com>,
        Marc Zyngier <maz@...nel.org>
Subject: Re: [PATCH] genirq/proc: Show percpu irq affinity

On Sat, Aug 22 2020 at 17:33, Yunfeng Ye wrote:
> On 2020/8/13 16:27, Thomas Gleixner wrote:
> For example, the cmdline "irqaffinity=0,1,126,127" on the 128 cores system：
>
> [root@...alhost ~]# cat /proc/irq/4/smp_affinity_list
> 0-1,126-127
>
> The irq 4 is "arch_timer" interrupt, which is a percpu interrupt.
>
> So is it necessary to show the percpu irq affinity correct?

Yes, it makes sense to do so, but you used the wrong check. The correct
one is:

irq_settings_is_per_cpu_devid()

which will not wreckage the output for other per cpu marked interrupts
which never set the percpu_affinity pointer with the obvious
consequences... The pointer would need a NULL check in any case, but it
might be more straight forward to update affinity when percpu_affinity
is initialized. Haven't looked in detail though.

Thanks,

        tglx