linux-kernel - Re: [RFC v3 1/2] powerpc/cpuidle: cpuidle wakeup latency based on IPI and timer events

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Message-ID: <87a5trvw88.fsf@mail.lhotse>
Date:   Wed, 13 Sep 2023 08:54:15 +1000
From:   Michael Ellerman <mpe@...erman.id.au>
To:     Aboorva Devarajan <aboorvad@...ux.vnet.ibm.com>,
        aboorvad@...ux.vnet.ibm.com, npiggin@...il.com,
        rmclure@...ux.ibm.com, arnd@...db.de, joel@....id.au,
        shuah@...nel.org, linux-kselftest@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        pratik.r.sampat@...il.com
Cc:     sshegde@...ux.vnet.ibm.com, srikar@...ux.vnet.ibm.com
Subject: Re: [RFC v3 1/2] powerpc/cpuidle: cpuidle wakeup latency based on
 IPI and timer events

Aboorva Devarajan <aboorvad@...ux.vnet.ibm.com> writes:
> From: Pratik R. Sampat <psampat@...ux.ibm.com>
>
> Introduce a mechanism to fire directed IPIs from a source CPU to a
> specified target CPU and measure the time incurred on waking up the
> target CPU in response.
>
> Also, introduce a mechanism to queue a hrtimer on a specified CPU and
> subsequently measure the time taken to wakeup the CPU.
>
> Define a simple debugfs interface that allows for adjusting the
> settings to trigger IPI and timer events on a designated CPU, and to
> observe the resulting cpuidle wakeup latencies.
>
> Reviewed-by: Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
> Signed-off-by: Pratik R. Sampat <psampat@...ux.ibm.com>
> Signed-off-by: Aboorva Devarajan <aboorvad@...ux.vnet.ibm.com>
> ---
>  arch/powerpc/Kconfig.debug                 |  10 ++
>  arch/powerpc/kernel/Makefile               |   1 +
>  arch/powerpc/kernel/test_cpuidle_latency.c | 154 +++++++++++++++++++++
  
I don't see anything here that's powerpc specific?

Which makes me wonder 1) could this be done with some existing generic
mechanism?, and 2) if not can this test code be made generic.

At the very least this should be Cc'ed to the cpuidle lists &
maintainers given it's a test for cpuidle latency :)

cheers