incorrect CPU usage readings in 2.2.19prex?

incorrect CPU usage readings in 2.2.19prex?

[safemode]

Is there something generally wrong with how linux determines total cpu
usage (via procmeter3 and top) when dealing with applications that are
threaded?   I routinely get 0% cpu usage when playing mpegs and mp3s and
some avi's even (Divx when using no software enhancement) ... Somehow i
doubt that the decoders are so streamlined that they produce <1% cpu
usage on the computer.  Does anyone know what's going on with this?
ps shows nearly 0% cpu usage in the threads as well.
    i've seen it in these programs
        freeamp
        mplayer

I've seen it in earlier 2.2.19 kernels but i'm using pre14 right now.

Re: incorrect CPU usage readings in 2.2.19prex?

[Jonathan Morton]

\>Is there something generally wrong with how linux determines total cpu
>usage (via procmeter3 and top) when dealing with applications that are
>threaded?   I routinely get 0% cpu usage when playing mpegs and mp3s and
>some avi's even (Divx when using no software enhancement) ... Somehow i
>doubt that the decoders are so streamlined that they produce <1% cpu
>usage on the computer.  Does anyone know what's going on with this?
>ps shows nearly 0% cpu usage in the threads as well.

If you're using a fairly new processor, this isn't at all new or surprising
- and yes, your MP3 decoders are really using under 1% CPU.  In general,
most processors with on-die or 'backside' L2 cache are capable of this.
The reason why older CPUs cannot manage this (eg. 486's and very early
Pentiums) is mostly due to memory bandwidth and thrashing the tiny L1
caches found on those processors - the lack of speed of the 486 itself is
also a factor, but not the only one.  Remember that a 486DX2/66 is
just-about capable of real-time MP3 decoding, and that CPU power has
increased around 50-fold from that point to the present day, not counting
improvements in memory and cache technology.

--------------------------------------------------------------
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mail:     chromi@cyberspace.org  (not for attachments)
big-mail: chromatix@penguinpowered.com
uni-mail: j.d.morton@lancaster.ac.uk

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Re: incorrect CPU usage readings in 2.2.19prex?

[Pavel Machek]

Hi!

> Is there something generally wrong with how linux determines total cpu
> usage (via procmeter3 and top) when dealing with applications that are
> threaded?   I routinely get 0% cpu usage when playing mpegs and mp3s and
> some avi's even (Divx when using no software enhancement) ... Somehow i
> doubt that the decoders are so streamlined that they produce <1% cpu
> usage on the computer.  Does anyone know what's going on with this?
> ps shows nearly 0% cpu usage in the threads as well.

CPU usage of programs that sleep after short computation is incorrectly computed

See badboy examples for code that gets 70% of cpu and is reported as getting
0%.

>     i've seen it in these programs
>         freeamp
>         mplayer
> 
> I've seen it in earlier 2.2.19 kernels but i'm using pre14 right now.
> 
> -
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