Re: [gentoo-user] Top values don't add up

[Alan McKinnon]

On Tuesday 19 August 2008 15:02:34 Håkon Alstadheim wrote:
> Top reports ~70% idle, while at the same time the topmost couple of
> processes are reported as using >70%CPU. Is there anything I could use
> that reports more sensible values ?
>
> I'm running the machine for multi-media-use, and I would like to make
> sure that I tune the media-programs to leave sufficcient cpu to handle
> the odd house-keeping task, while at the same time doing as much
> post-processing for image and sound quality as possible. Is there a way
> to get top to make sense, or are there other tools you good people would
> recommend ?

Let the kernel do what it does best - scheduling. You stay away from this as 
this is the one thing you do worst. Unless you have some weird workload it is 
highly unlikely that you will even remotely approach the kernel's choices for 
scheduler efficiency, much less better them.

The kernel is designed to give every process a fair shot at running, this is a 
process that requires millions of decisions a second.

The reason that top's output does not add up is that top (plus free and most 
of the contents of /proc as well) is basically lying through it's teeth. All 
these tools read the various files in /proc to get their data. By the time top 
has read the last file it wants, the ones before it have changed many 
thousands of times over. So basically you get a snapshot view of what the 
system is averaging, and you are not interested in the exact number you see on 
the screen (because you can't trust it), but you are interested in the general 
trend over time (as you can trust that)

-- 
alan dot mckinnon at gmail dot com