linux-kernel - Re: Hyperthreading performance oddities

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Message-ID: <47D14526.2070103@gmail.com>
Date:	Fri, 07 Mar 2008 08:37:42 -0500
From:	Andrew Buehler <abuehler.kernel@...il.com>
To:	Frederik Deweerdt <deweerdt@...e.fr>
CC:	belcampo <belcampo@...net.nl>, linux-kernel@...r.kernel.org
Subject: Re: Hyperthreading performance oddities

(I'm aware that this could be considered thread necromancy, but I
haven't yet seen any indication that that is considered a bad thing in
these here parts; if it is, then I apologize, and upon being informed of
the fact will undertake to not commit such again.)

On 2/22/2008 5:06 AM, Frederik Deweerdt wrote:

> Hello Henk,
> 
> On Fri, Feb 22, 2008 at 10:36:01AM +0100, belcampo wrote:
> 
>> Kernel 2.6.22.9 smp hyperthreading
>> BENCHMARKs: VC: 334.042s VO:   0.053s A:   0.000s Sys:   4.049s =  338.143s
>> Kernel 2.6.22.9 nonsmp/hyperthreading
>> BENCHMARKs: VC: 262.008s VO:   0.031s A:   0.000s Sys:   3.528s =  265.567s
>> with 2.6.17 kernel smp/hyperthreading pentium-pro as CPU
>> BENCHMARKs: VC: 245.175s VO:   0.050s A:   0.000s Sys:   2.479s =  247.704s
>> with 2.6.17 kernel smp/hyperthreading pentium4 optimized kernel
>> BENCHMARKs: VC: 227.992s VO:   0.051s A:   0.000s Sys:   2.551s =  230.594s
> 
> I'm not familiar with mplayer benchmarks, what do they actually 
> measure?

I don't know if this discussion got continued privately, but on the
assumption that it didn't, I think I can give at least a basic answer to
this.

The VC: value is the amount of time spent in the video-codec code during
that run, the VO: value is the amount of time spent in the video-output
code, the A: is the amount of time spent in (ISTR) audio processing -
though whether codec or audio-output or audio filters etc. is unclear, I
remember there being separate values for those rather than their being
lumped under one header- and the Sys: value is I believe the amount of
time spent in system calls.

(For the record: I'm a long-time lurker and occasional, largely
non-code, contributor on the MPlayer development lists, but I've never
had occasion to look at the code behind or the logic involved in the
-benchmark output.)

-- 
    Andrew Buehler
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