Messages in this thread |  | | Date | Tue, 27 Jul 2021 15:29:44 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH 1/1] sched/fair: improve yield_to vs fairness |
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On Fri, Jul 23, 2021 at 05:21:37PM +0100, Mel Gorman wrote:
> I'm still not a fan because vruntime gets distorted. From the docs > > Small detail: on "ideal" hardware, at any time all tasks would have the same > p->se.vruntime value --- i.e., tasks would execute simultaneously and no task > would ever get "out of balance" from the "ideal" share of CPU time > > If yield_to impacts this "ideal share" then it could have other > consequences.
Note that we already violate this ideal both subtly and explicitly.
For an example of the latter consider pretty much the entirety of place_entity() with GENTLE_FAIR_SLEEPERS being the most egregious example.
That said; adding to vruntime will only penalize the task itself, while subtracting from vruntime will penalize everyone else. And in that sense addition to vruntime is a safe option.
I've not fully considered the case at hand; just wanted to give some context.
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