Messages in this thread | | | Subject | Re: Some ideas about % of CPU for a process | From | Valdis.Kletnieks@vt ... | Date | Fri, 12 Nov 2004 14:30:10 -0500 |
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On Fri, 12 Nov 2004 19:55:33 +0100, Ed Schouten said:
> On Fri 12 Nov 2004 03:47 PM, Diego wrote: > > I'm trying to define a % of cpu for a process, but i don?t have idea > > about how i can do it. For example, i said that my process need 40% of > > CPU during its lifetime, how can i do it in kernel 2.6? > > Thanks for ideas. > > Why don't you 'ps' the process and divide the running time through the > starting time?
I think he's trying to make a 40% *allotment* - as in "this number cruncher is authorized to take 40% of the CPU for the next 6 hours". The devil always ends up being in the details however - things I've seen scheduling systems fail with in the past:
1) Process is allowed to take 40% of the CPU, but so overcommits memory that it can't actually *get* it because 65% of the time, the system is in a page wait from the swap partition. (iterate across any *other* shared resource that isn't directly tied to CPU).
2) Process is allowed to take 40% of the CPU, and no more - and somebody gets torqued off because the system is 60% idle.
3) Process is allowed to take 40% at all times, and more if available - and somebody gets torqued off because it's slow to notice the system has bogged down - so it's still getting 60% for another 2-3 minutes when we're loaded before the scheduler catches up.
4) And you always get the whiner who complains it's getting 39% or 41%. ;)
Saying "40% of the CPU" is easy - the fun is in the corner cases... [unhandled content-type:application/pgp-signature] | |