Re: [ck] [REPORT] cfs-v5 vs sd-0.46

[Michael Gerdau <mgd@technosis.de>]

> > with cfs-v5 finally booting on my machine I have run my daily
> > numbercrunching jobs on both cfs-v5 and sd-0.46, 2.6.21-v7 on
> > top of a stock openSUSE 10.2 (X86_64).
> 
> Thanks for testing.

I actually enjoyed it -- the more extensive test I had promised
two days ago is almost finished. There is just one test I have
yet to (re)run and I will have a slot for it later today so I'll
mail out the results comparing
    2.6.21-rc7 (mainline)
    2.6.21-rc7-sd046
    2.6.21-rc7-cfs-v6-rc2 (X @ nice 0)
    2.6.21-rc7-cfs-v6-rc2 (X @ nice -10)
during the early afternoon (my time).

> You have 3 tasks and only 2 cpus. The %cpu is the percentage of the cpu the 
> task is currently on that it is using; it is not the percentage of 
> the "overall cpu available on the machine". Since you have 3 tasks and 2 
> cpus, the extra task will always be on one or the other cpu taking half of 
> the cpu but never on both cpus.

I had assumed that given the interval of 3 sec the three tasks would
be evenly distributed among the 2 CPUs thus resulting in a CPU% of
66 each because that's what they get in the long run anyway.

Apparently 3 sec is too short an interval to see this.

> What is important is that if all three tasks are fully cpu bound and started 
> at the same time at the same nice level, that they all receive close to the 
> same total cpu time overall showing some fairness is working as well. This 
> should be the case no matter how many cpus you have.

They are started via 'make -j3' which implies they start at the
same time (i.e. within a few msec). They initially load some data
and then perform extensive computations on that data.

Best,
Michael
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