linux-kernel - RE: Performance drop on Baytrail with 4.5-rc2

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Date:	Tue, 2 Feb 2016 18:56:33 +0100 (CET)
From:	Thomas Voegtle <tv@...96.de>
To:	"Longepe, Philippe" <philippe.longepe@...el.com>
cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Gasparini, Stephane" <stephane.gasparini@...el.com>,
	"Wysocki, Rafael J" <rafael.j.wysocki@...el.com>
Subject: RE: Performance drop on Baytrail with 4.5-rc2

On Tue, 2 Feb 2016, Longepe, Philippe wrote:

> Hi Thomas,
>
> Yes, this new algorithm is intented to improve the performance versus power efficiency.
>
> Can you please provide us the exact instructions to reproduce your test ?

Hi,

my benchmark which I used is a little bit weird, so I tried to strip it
down a little.

The sample I used: https://32h.de/tv/test.vdr

I downloaded a static built version from
http://johnvansickle.com/ffmpeg/

I used the 64bit v2.8.6 binary.
   (md5 of ffmpeg binary: 2989d50b4b13cb1e549955522fd7d311)

And then I did:
time -p ./ffmpeg -v 0 -y -i test.vdr -preset veryfast -vf scale=320:208
-strict -2  -f mp4 /dev/null

Very interesting: you only get a difference between 4.5-rc2-with-revert 
and 4.5-rc2 with the downscaling. When you remove "-vf scale=320:208", you 
get the same times on 4.5-rc2-with-revert and the unmodified 4.5-rc2. See 
below:

with downscale
==============
4.5-rc2-with-revert
real 93.16
real 92.96
real 93.24

4.5-rc2
real 100.00
real 99.31
real 99.12

without "-vf scale=320:208"
===========================
4.5-rc2-with-revert
real 157.59
real 157.27
real 157.58

4.5-rc2
real 157.49
real 157.68
real 157.53

I'm confused, but I hope this helps? Do you need anything else?

Thanks in advance.

    Thomas