On 02 Apr 2023 04:40:20 +0200 Mike Galbraith <efault@xxxxxx> > On Sun, 2023-04-02 at 07:23 +0800, Hillf Danton wrote: > > On 31 Mar 2023 17:26:51 +0200 Vincent Guittot <vincent.guittot@xxxxxxxxxx> > > > > > > I wanted to stress this situation with a simple use case but it seems > > > that even without changing the slice, there is a fairness problem: > > > > > > Task A always run > > > Task B loops on : running 1ms then sleeping 1ms > > > default nice and latency nice prio bot both > > > each task should get around 50% of the time. > > > > > > The fairness is ok with tip/sched/core > > > but with eevdf, Task B only gets around 30% > > > > Convincing evidence for glitch in wakeup preempt. > > If you turn on PLACE_BONUS, it'll mimic FAIR_SLEEPERS.. but if you then > do some testing, you'll probably turn it right back off. > > The 50/50 split in current code isn't really any more fair, as soon as > you leave the tiny bubble of fairness, it's not the least bit fair. > Nor is that tiny bubble all rainbows and unicorns, it brought with it > benchmark wins and losses, like everything that changes more than > comments, its price being service latency variance. > > The short term split doesn't really mean all that much, some things > will like the current fair-bubble better, some eevdf virtual deadline > math and its less spiky service. We'll see. > > I'm kinda hoping eevdf works out, FAIR_SLEEPERS is quite annoying to > squabble with. Yeah no matter whatever role FAIR_SLEEPERS could play next week, this paves a brick for Vlastimil Babka to take it over leaving Peter happy to sit back with netflix on.
