Messages in this thread | ![/](/images/icornerl.gif) | | Subject | Re: [RFC 2/5] sched: Add CPU rate soft caps | From | Mike Galbraith <> | Date | Fri, 26 May 2006 13:30:19 +0200 |
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On Fri, 2006-05-26 at 21:17 +1000, Con Kolivas wrote: > On Friday 26 May 2006 21:15, Mike Galbraith wrote: > > On Fri, 2006-05-26 at 20:48 +1000, Con Kolivas wrote: > > > On Friday 26 May 2006 14:20, Peter Williams wrote: > > > > 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. > > > > Hmm. I think that came out kinda back-assward. You meant "the array > > swap happens very frequently _unless_..." No? > > No I didn't. If all you are doing is compiling code then the array swap will > happen often as they will always use up their full timeslice and expire. > Therefore an array swap will follow shortly afterwards.
Afterward being possibly ages. Frequent array switch happens when you have mostly sleepy processes, not cpu bound. But whatever.
> > But anyway, I can't think of any reason to hold back an uncontested > > resource. > > If you are compiling applications it's a contested resource.
These zero capped tasks are at the bottom of the heap. They won't be selected if there's any other runnable task, so it's not contested.
-Mike
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