Messages in this thread | | | Subject | Re: Interesting analysis of linux kernel threading by IBM | Date | Fri, 21 Jan 2000 11:12:50 -0300 | From | Horst von Brand <> |
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"Davide Libenzi" <davidel@maticad.it> said:
[...]
> 300 running processes ( I say running not in runqueue ) > 12 up to 35 in runqueue > I get an 83% performance improvement
I have yet to see a machine capable of such a load. And when I see it, it will be a cluster or a massive SMP machine anyway. Load averages here rarely go to 10 or so, for multiuser machines that do time as servers on the side. Not that this is a large shop, but I'say we are rather on the high side of average around here.
> 2 running processes ( that switch at the same rate of 300 ) > I get 11% up to 15% performance loss
This is a personal workstation scenario. There you have peole that are worried about minimizing latencies (long thread about that recently) for playing MP3s or other not-so-soft realtime tasks, and getting the most performance out of the machine.
> But the fact is that normally 2 tasks switches at a very lower factor then > 300.
Why? That depends mostly on the tasks, and if the tasks are the same, this should not change very much (unless the machine is swamped with interrupts, and then your problem is another one).
I'd like to see hard numbers of _real_ workloads that'd allow me to relate your benchamrk numbers to reality. I'm not too worried about a few percent increase in schedule() time on a mostly idle personal machine, I'm worried about that few percent on a loaded machine (10 or so tasks around here, usually) that is _far_ from your hundreds of running tasks scenarios. -- Dr. Horst H. von Brand mailto:vonbrand@inf.utfsm.cl Departamento de Informatica Fono: +56 32 654431 Universidad Tecnica Federico Santa Maria +56 32 654239 Casilla 110-V, Valparaiso, Chile Fax: +56 32 797513
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