On Wed, Oct 03, 2007 at 11:10:58AM +0200, Ingo Molnar wrote: > > * Jarek Poplawski <[EMAIL PROTECTED]> wrote: > > > On Wed, Oct 03, 2007 at 10:16:13AM +0200, Ingo Molnar wrote: > > > > > > * Jarek Poplawski <[EMAIL PROTECTED]> wrote: > > > > > > > > firstly, there's no notion of "timeslices" in CFS. (in CFS tasks > > > > > "earn" a right to the CPU, and that "right" is not sliced in the > > > > > traditional sense) But we tried a conceptually similar thing [...] > > > > > > > > >From kernel/sched_fair.c: > > > > > > > > "/* > > > > * Targeted preemption latency for CPU-bound tasks: > > > > * (default: 20ms, units: nanoseconds) > > > > * > > > > * NOTE: this latency value is not the same as the concept of > > > > * 'timeslice length' - timeslices in CFS are of variable length. > > > > * (to see the precise effective timeslice length of your workload, > > > > * run vmstat and monitor the context-switches field) > > > > ..." > > > > > > > > So, no notion of something, which are(!) of variable length, and which > > > > precise effective timeslice lenght can be seen in nanoseconds? (But > > > > not timeslice!) > > > > > > You should really read and understand the code you are arguing about :-/ > > > > Maybe you could help me with better comments? IMHO, it would be enough > > to warn new timeslices have different meaning, or stop to use this > > term at all. [...] > > i'm curious, what better do you need than the very detailed comment > quoted above? Which bit of "this latency value is not the same as the > concept of timeslice length" is difficult to understand? The timeslices > of tasks (i.e. the time they spend on a CPU without scheduling away) is > _not_ maintained directly in CFS as a per-task variable that can be > "cleared", it's not the metric that drives scheduling. Yes, of course > CFS too "slices up CPU time", but those slices are not the per-task > variables of traditional schedulers and cannot be 'cleared'.
It's not about this comment alone, but this comment plus "no notion" comment, which appears in sched-design-CFS.txt too. > > > [...] (Btw, in -rc8-mm2 I see new sched_slice() function which seems > > to return... time.) > > wrong again. That is a function, not a variable to be cleared. (Anyway, > the noise/signal ratio is getting increasingly high in this thread with > no progress in sight, so i cannot guarantee any further replies - > possibly others will pick up the tab and explain/discuss any other > questions that might come up. Patches are welcome of course.) I can't see anything about clearing. I think, this was about charging, which should change the key enough, to move a task to, maybe, a better place in a que (tree) than with current ways. Jarek P. PS: Don't you think that a nice argue with some celebrity, like Ingo Molnar himself, is by far more interesting than those dull patches? - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
