linux-kernel - Re: [PATCH 0/3] cpuidle: small improvements & fixes for menu governor (resend)

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Message-ID: <563C0FE8.8070301@redhat.com>
Date:	Thu, 05 Nov 2015 21:26:48 -0500
From:	Rik van Riel <riel@...hat.com>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>
CC:	linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
	rafael.j.wysocki@...el.com, arjan@...ux.intel.com,
	len.brown@...el.com, daniel.lezcano@...aro.org
Subject: Re: [PATCH 0/3] cpuidle: small improvements & fixes for menu governor
 (resend)

On 11/05/2015 05:34 PM, Rafael J. Wysocki wrote:
> On Tuesday, November 03, 2015 05:34:16 PM riel@...hat.com wrote:
>> While working on a paravirt cpuidle driver for KVM guests, I
>> noticed a number of small logic errors in the menu governor
>> code.
>>
>> These patches should get rid of some artifacts that can break
>> the logic in the menu governor under certain corner cases, and
>> make idle state selection work better on CPUs with long C1 exit
>> latencies.
>>
>> I have not seen any adverse effects with them in my (quick)
>> tests. As expected, they do not seem to do much on systems with
>> many power states and very low C1 exit latencies and target residencies. 
> 
> Thanks!
> 
> The patches look good to me.
> 
> I might apply [1-2/3] right away, but I'm a bit hesitant about the [3/3] (I'd
> like it to spend some time in linux-next before it goes to Linus).  Also, we've
> lived without these changes for quite some time and I don't want to stretch the
> process too much, so I'll queue them up for v4.5 if that's not a problem.

Not a problem at all. I am all for taking these changes carefully,
and seeing what happens.

I did some basic testing with it, but the permutations of what
can happen with cpuidle management are just too many to predict
in advance everything that could happen.

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