Messages in this thread |  | | | Subject | Re: decaying average for %CPU | | From | Albert Cahalan <> | | Date | 16 Oct 2003 23:00:29 -0400 |
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On Thu, 2003-10-16 at 22:56, Nick Piggin wrote: > Albert Cahalan wrote: > > >The UNIX standard requires that Linux provide > >some measure of a process's "recent" CPU usage. > >Right now, it isn't provided. You might run a > >CPU hog for a year, stop it ("kill -STOP 42") > >for a few hours, and see that "ps" is still > >reporting 99.9% CPU usage. This is because the > >kernel does not provide a decaying average. > > I think the kernel provides enough info for userspace to do > the job, doesn't it?
I'm pretty sure not. Linux provides:
per-process start time current time per-process total (lifetime) CPU usage units of time measurement (awkwardly) boot time
>From that you can compute %CPU over the whole life of the process. This does not meet the requirements of the UNIX standard.
What we do for load average is about right, except that per-process values can't all get updated at the same time. So the algorithm needs to be adjusted a bit to allow for that
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