CPU usage confusion

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digid
Posts: 174
Joined: Sat Nov 28, 2009 10:29 pm

CPU usage confusion

Post by digid » Thu Mar 03, 2011 10:26 pm

Just downloaded the latest Live beta (8.2.2b4), and it seems more CPU hungry than ever before.

This means it's very sensitive to other activity on the MacBook Pro, like switching to other programs. This will result in a glitch during playback on my system.

I don't get the CPU usage report at all. Look at the screenshot below. CPU usage in Live says between 22-23%, but then I check the Activity Monitor on my Macbook Pro and it says around 99%!

This doesn't make sense to me. Live is making it look like it's not straining my CPU at all, and that there's plenty of juice left. However, the activity montior is telling me this is about as much power as I can get ...

Look at this image:

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8O
Posts: 5502
Joined: Fri Mar 28, 2008 9:29 am
Location: Berlin

Re: CPU usage confusion

Post by 8O » Thu Mar 03, 2011 10:35 pm

Dunno if this helps... from: http://forum.ableton.com/viewtopic.php? ... 83&start=0
[dfi] wrote:Hi MFSnakes,

check the Live manual on page 502:
The Control Bar’s CPU meter displays how much of the computer’s computational potential is
currently being used. For example, if the displayed percentage is 10 percent, the computer
is just coasting along. If the percentage is 100 percent, the processing is being maxed
out it’s likely that you will hear gaps, clicks or other audio problems.

Note that the CPU meter takes into account only the load from processing audio, not other tasks the computer
performs (e.g., managing Live’s user interface).


best,
dfi
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digid
Posts: 174
Joined: Sat Nov 28, 2009 10:29 pm

Re: CPU usage confusion

Post by digid » Thu Mar 03, 2011 10:50 pm

8O wrote:Dunno if this helps... from: http://forum.ableton.com/viewtopic.php? ... 83&start=0
[dfi] wrote:Hi MFSnakes,

check the Live manual on page 502:
The Control Bar’s CPU meter displays how much of the computer’s computational potential is
currently being used. For example, if the displayed percentage is 10 percent, the computer
is just coasting along. If the percentage is 100 percent, the processing is being maxed
out it’s likely that you will hear gaps, clicks or other audio problems.

Note that the CPU meter takes into account only the load from processing audio, not other tasks the computer
performs (e.g., managing Live’s user interface).


best,
dfi

Hmm, not sure it does. This would mean Live is doing an awful amount of work that is not related to processing audio, and that, of course, would mean LIve has simply been badly/strangely coded.
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steko
Posts: 3350
Joined: Thu Jan 22, 2009 8:29 pm

Re: CPU usage confusion

Post by steko » Thu Mar 03, 2011 11:08 pm

What you see is perfectly normal. I get the same. OS X's Activity Monitor & Live's CPU meter are not comparable.

FromFriedemann (Ableton) in an old thread (in a now closed Live Beta forum):
Friedemann wrote:Hi,

the CPU meter in Live works differently than the usual CPU meters in the operating system.

In Live you see the ratio of the time that was actually needed to compute the audio signal and the time that
is available to compute it. The latter is just determined by the sample rate of the audio interface, i.e. at 48kHz
sample rate you need to compute 48000 samples in one second, if it takes longer, there will be drop-outs.

Therefore, values below 100% mean that the samples were faster calculated
than needed by the audio interface while values above 100% mean that calculating the samples took too long
for being delivered to the audio interface on time. In the multi-processor-case the slowest path, i.e. the processor that has to calculate most, determines that number.

On the OS level you usually see how much time a certain processor (or all together) devotes to a certain process.

Although both meters show '%' values, they are not really comparable.

Best, Friedemann
BTW 98% in OS X's Activity Monitor means one core. With my 8 core, full CPU would be 800.
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