linux-kernel - RE: [RFT][PATCH v7 5/8] cpuidle: Return nohz hint from cpuidle

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Date:   Wed, 21 Mar 2018 11:23:22 -0700
From:   "Doug Smythies" <dsmythies@...us.net>
To:     "'Thomas Ilsche'" <thomas.ilsche@...dresden.de>,
        "'Rafael J. Wysocki'" <rafael@...nel.org>
Cc:     "'Peter Zijlstra'" <peterz@...radead.org>,
        "'Frederic Weisbecker'" <fweisbec@...il.com>,
        "'Thomas Gleixner'" <tglx@...utronix.de>,
        "'Paul McKenney'" <paulmck@...ux.vnet.ibm.com>,
        "'Rik van Riel'" <riel@...riel.com>,
        "'Aubrey Li'" <aubrey.li@...ux.intel.com>,
        "'Mike Galbraith'" <mgalbraith@...e.de>,
        "'LKML'" <linux-kernel@...r.kernel.org>,
        "'Linux PM'" <linux-pm@...r.kernel.org>,
        "Doug Smythies" <dsmythies@...us.net>
Subject: RE: [RFT][PATCH v7 5/8] cpuidle: Return nohz hint from cpuidle_select()

On 2018.03.21 11:00 Thomas Ilsche wrote:
> On 2018-03-21 15:36, Rafael J. Wysocki wrote:
>> 
>> So please disregard this one entirely and take the v7.2 replacement
>> instead of it:https://patchwork.kernel.org/patch/10299429/
>> 
>> The current versions (including the above) is in the git branch at
>> 
>>   git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm.git \
>>   idle-loop-v7.2
>
> With v7.2 (tested on SKL-SP from git) I see similar behavior in idle
> as with v5: several cores which just keep the sched tick enabled.
> Worse yet, some go only in C1 (not even C1E!?) despite sleeping the
> full sched tick.
> The resulting power consumption is ~105 W instead of ~ 70 W.
>
> https://wwwpub.zih.tu-dresden.de/~tilsche/powernightmares/v7_2_skl_sp_idle.png
>
> I have briefly ran v7 and I believe it was also affected.

I am not able to repeat your issues anymore.
Idle powers were fine with V7, on my test computer.
I have not done thorough idle tests with V7.2, but they looked O.K.

As for the high frequency loop stuff, I no longer see any issues there
either. I tried several loops frequencies, and did one for a couple of hours.

I'll try again later today, as there is a test running now (frequency sweep)
that takes about 4 hours.

... Doug