Re: How to increase maximum user cpu usage allowed on a multi core system?

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On 11.03.2015, stan wrote: 

> I don't see why this is necessary.  The system is showing 470%
> idle.  So the kernel cpu scheduler shouldn't need to limit the job to a
> single core maximum usage.

I just tried a simple "make" on an 8-core machine. There was exactly one
compile process, and it's 100% load was distributed over 3 cores. So nothing
wrong with that one. If you run 100% on one core or 100% distributed over
multiple cores is, in terms of efficacy, the same.

> Even if it leaves some margin for error, it
> should still be using more than a single core equivalent.  The kernel
> programmers are smart folks.  Not to mention that they do large
> compilations on multi-core machines often.  I doubt that they hard
> coded this kind of behavior into the kernel.

It's the limiting to one process which causes what you observe. 1 process can
not get more resources that 100%. The CPU scheduler handles how they are
distributed.

> So there must be a setting that is limiting the kernel scheduler in some way.
> Maybe it's the scheduler that is being used.  I'm using 'on demand' rather than
> 'performance'.

Ondemand and performance affect the cpufreq, not the load balancing or the
involvement of different cores.

> 'Performance' sounds like it keeps everything at full
> rev all the time.

No. It keeps every core running at full speed all the way, which has nothing to
do with how the load is balanced between different cores. 

> I'll keep plugging away, reading and experimenting, until I get it or
> give up.

Use "make -j" when compiling and be happy :-)

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