linux-kernel - Re: [PATCH v3 03/16] arm64: Allow IPIs to be handled as normal interrupts

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Date:   Mon, 19 Oct 2020 17:00:09 +0100
From:   Valentin Schneider <valentin.schneider@....com>
To:     Vincent Guittot <vincent.guittot@...aro.org>
Cc:     Marc Zyngier <maz@...nel.org>,
        LAK <linux-arm-kernel@...ts.infradead.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Will Deacon <will@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Russell King <linux@....linux.org.uk>,
        Thomas Gleixner <tglx@...utronix.de>,
        Jason Cooper <jason@...edaemon.net>,
        Sumit Garg <sumit.garg@...aro.org>,
        Florian Fainelli <f.fainelli@...il.com>,
        Gregory Clement <gregory.clement@...tlin.com>,
        Andrew Lunn <andrew@...n.ch>,
        Saravana Kannan <saravanak@...gle.com>,
        Android Kernel Team <kernel-team@...roid.com>
Subject: Re: [PATCH v3 03/16] arm64: Allow IPIs to be handled as normal interrupts

Hi,

On 19/10/20 16:43, Vincent Guittot wrote:
> On Mon, 19 Oct 2020 at 15:04, Marc Zyngier <maz@...nel.org> wrote:
>> Since you are running perf, can you spot where the overhead occurs?
>
> hmm... Difficult to say because tracing the bench decreases a lot the
> result. I have pasted the perf reports.
>

<snip>

> I have only put symbol with overhead above 1%
>
> so _raw_spin_unlock_irq, schedule and __schedule seem the most
> impacted but i can't get any conclusion
>

AFAICT on TX2 you should be able to run these and get some more details
within IRQ-disabled regions:

https://lore.kernel.org/linux-arm-kernel/20200924110706.254996-1-alexandru.elisei@arm.com/

(they should be on linux-next)

> I can sent you perf.data files if you want
>
>
>>
>> Thanks,
>>
>>          M.
>> --
>> Jazz is not dead. It just smells funny...