From: Michael Ellerman <mpe@ellerman•id.au>
To: Gautham R Shenoy <ego@linux•vnet.ibm.com>
Cc: "Gautham R. Shenoy" <ego@linux•vnet.ibm.com>,
"Rafael J. Wysocki" <rjw@rjwysocki•net>,
Daniel Lezcano <daniel.lezcano@linaro•org>,
Stewart Smith <stewart@linux•vnet.ibm.com>,
Michael Neuling <mikey@neuling•org>,
Vaidyanathan Srinivasan <svaidy@linux•vnet.ibm.com>,
Shilpasri G Bhat <shilpa.bhat@linux•vnet.ibm.com>,
Akshay Adiga <akshay.adiga@linux•vnet.ibm.com>,
Nicholas Piggin <npiggin@gmail•com>,
linuxppc-dev@lists•ozlabs.org, linux-kernel@vger•kernel.org,
linux-pm@vger•kernel.org
Subject: Re: [PATCH] cpuidle:powernv: Make the snooze timeout dynamic.
Date: Tue, 05 Jun 2018 22:18:40 +1000 [thread overview]
Message-ID: <87zi09mnof.fsf@concordia.ellerman.id.au> (raw)
In-Reply-To: <20180605084529.GA5656@in.ibm.com>
Gautham R Shenoy <ego@linux•vnet.ibm.com> writes:
> Hello Michael,
>
> On Mon, Jun 04, 2018 at 09:27:40PM +1000, Michael Ellerman wrote:
>> "Gautham R. Shenoy" <ego@linux•vnet.ibm.com> writes:
>>
>> > From: "Gautham R. Shenoy" <ego@linux•vnet.ibm.com>
>> >
>> > The commit 78eaa10f027c ("cpuidle: powernv/pseries: Auto-promotion of
>> > snooze to deeper idle state") introduced a timeout for the snooze idle
>> > state so that it could be eventually be promoted to a deeper idle
>> > state. The snooze timeout value is static and set to the target
>> > residency of the next idle state, which would train the cpuidle
>> > governor to pick the next idle state eventually.
>> >
>> > The unfortunate side-effect of this is that if the next idle state(s)
>> > is disabled, the CPU will forever remain in snooze, despite the fact
>> > that the system is completely idle, and other deeper idle states are
>> > available.
>>
>> That sounds like a bug, I'll add?
>
> Yes, this is a bug-fix for a customer scenario which we encountered
> recently.
OK, the change log could have used some more scary words to make that
clearer ;)
I changed the subject to:
cpuidle: powernv: Fix promotion from snooze if next state disabled
Which hopefully makes sense.
>> Fixes: 78eaa10f027c ("cpuidle: powernv/pseries: Auto-promotion of snooze to deeper idle state")
>> Cc: stable@vger•kernel.org # v4.2+
>
> This patch applies cleanly from v4.13 onwards. Prior to that there are
> some (minor) conflicts.
>
> Should I spin a version separately for the prior stable versions ?
Yes please, that would be great.
You might want to avoid "=====" in the change log too, as patchwork and
possibly other tools will think it's part of the diff.
cheers
next prev parent reply other threads:[~2018-06-05 12:18 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-05-31 12:15 [PATCH] cpuidle:powernv: Make the snooze timeout dynamic Gautham R. Shenoy
2018-05-31 14:51 ` Balbir Singh
2018-06-01 4:54 ` Gautham R Shenoy
2018-06-02 0:16 ` Balbir Singh
2018-06-04 11:27 ` Michael Ellerman
2018-06-05 3:47 ` Stewart Smith
2018-06-05 8:45 ` Gautham R Shenoy
2018-06-05 12:18 ` Michael Ellerman [this message]
2018-06-05 15:19 ` Michael Ellerman
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