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SubjectRe: [RFC][PATCH] O(1) Entitlement Based Scheduler
Albert Cahalan wrote:
> John Lee writes:
>
>
>>The usage rates for each task are estimated using Kalman
>>filter techniques, the estimates being similar to those
>>obtained by taking a running average over twice the filter
>>_response half life_ (see below). However, Kalman filter
>>values are cheaper to compute and don't require the
>>maintenance of historical usage data.
>
>
> Linux dearly needs this. Please separate out this part
> of the patch and send it in.

This information can be determined from the SleepAVG: field in the
/proc/<pid>/status and /proc/<tgid>/task/<pid>/status files by
subtracting the value there from 100. Without our patch this value is a
directly calculated estimated of the task's sleep rate which is
available because it used by the O(1) scheduler's heuristics. With our
patches, it is calculated from our estimate of the task's usage because
we dispensed with the sleep average calculations as they are no longer
needed. We decided to still report sleep average in the status file
because we were reluctant to alter the contents of such files in case we
broke user space programs.

>
> Right now, Linux does not report the recent CPU usage
> of a process. The UNIX standard requires that "ps"
> report this; right now ps substitutes CPU usage over
> the whole lifetime of a process.
>
> Both per-task and per-process (tid and tgid) numbers
> are needed. Both percent and permill (1/1000) units
> get reported, so don't convert to integer percent.

I think a modification to fs/proc/array.c to make this field a per
million rather than a percent value would satisfy your needs. It would
be a very small change but there would be concerns about breaking
programs that rely on it being a percentage.

Peter
--
Dr Peter Williams, Chief Scientist peterw@aurema.com
Aurema Pty Limited Tel:+61 2 9698 2322
PO Box 305, Strawberry Hills NSW 2012, Australia Fax:+61 2 9699 9174
79 Myrtle Street, Chippendale NSW 2008, Australia http://www.aurema.com

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