Messages in this thread | | | From | Con Kolivas <> | Subject | Re: [RFC 2/5] sched: Add CPU rate soft caps | Date | Fri, 26 May 2006 20:48:52 +1000 |
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On Friday 26 May 2006 14:20, Peter Williams wrote: > This patch implements (soft) CPU rate caps per task as a proportion of a > single CPU's capacity expressed in parts per thousand. The CPU usage > of capped tasks is determined by using Kalman filters to calculate the > (recent) average lengths of the task's scheduling cycle and the time > spent on the CPU each cycle and taking the ratio of the latter to the > former. To minimize overhead associated with uncapped tasks these > statistics are not kept for them. > > Notes: > > 1. To minimize the overhead incurred when testing to skip caps processing > for uncapped tasks a new flag PF_HAS_CAP has been added to flags.
[ot]I'm sorry to see an Australian adopt American spelling [/ot]
> 3. Enforcement of caps is not as strict as it could be in order to > reduce the possibility of a task being starved of CPU while holding > an important system resource with resultant overall performance > degradation. In effect, all runnable capped tasks will get some amount > of CPU access every active/expired swap cycle. This will be most > apparent for small or zero soft caps.
The array swap happens very frequently if there are nothing but heavily cpu bound tasks, which is not an infrequent workload. I doubt the zero caps are very effective in that environment.
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