linux-kernel - RE: [regression] cross core scheduling frequency drop bisected to 0c313cb20732

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Date:	Sat, 9 Apr 2016 00:17:52 -0700
From:	"Doug Smythies" <dsmythies@...us.net>
To:	"'Mike Galbraith'" <umgwanakikbuti@...il.com>
Cc:	"'Peter Zijlstra'" <peterz@...radead.org>,
	"'Rafael J. Wysocki'" <rafael.j.wysocki@...el.com>,
	"'LKML'" <linux-kernel@...r.kernel.org>,
	"'Linux PM list'" <linux-pm@...r.kernel.org>,
	"'Rik van Riel'" <riel@...hat.com>,
	"'Rafael J. Wysocki'" <rjw@...ysocki.net>
Subject: RE: [regression] cross core scheduling frequency drop bisected to 0c313cb20732

On 2016.04.08 15:19 Doug Smythies wrote:
> On 2016.04.08 14:00 Rafael J. Wysocki wrote:
>> On Friday, April 08, 2016 08:50:54 AM Mike Galbraith wrote:
>>> On Fri, 2016-04-08 at 08:45 +0200, Peter Zijlstra wrote:
>>> 
>>>> Cute, I thought you used governor=performance for your runs?
>>> 
>>> I do, and those numbers are with it thus set.

>> Well, this is a trade-off.
>>
>> 4.5 introduced a power regression here so this one goes back to the previous
>> state of things.

> Mike:
>
> Could you send me, or point me to, the program "pipe-test"?
> So far, I have only found one, but it is both old and not
> the same program you are running (based on print statements).
>
> I realize I might not be to recreate your problem scenario anyhow,
> I just want to try.

I still didn't find the exact same program, but I think I found some
earlier version of the correct test.

I get (long term average):
Kernel 4.4.0-17: Powersave 3.93 usecs/loop ; Performance 3.93 usecs/loop 0.89
Kernel 4.5-rc7: Powersave 3.47 usecs/loop ; Performance 3.51 usecs/loop  1.00
Kernel 4.6-rc1: Powersave 3.84 usecs/loop ; Performance 3.88 usecs/loop  0.90

So, similar results (so far, I didn't try reverted yet).

... Doug