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SubjectRe: [PATCH 7/8] sched: non-zero lag renice
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On Fri, 2008-10-24 at 11:47 -0600, Chris Friesen wrote:
> Peter Zijlstra wrote:
>
> > Then renicing, esp when lowering nice value (getting heavier), its possible
> > to get into a starvation scenario. If you got too much runtime as a very
> > light task, you get shot way far too the right, which means you'll have to
> > wait for a long time in order to run again.
> >
> > If during that wait you get reniced down, fairness would suggest you get run
> > earlier, because you deserve more time.
> >
> > This can be solved by scaling the vruntime so that we keep the real-time
> > lag invariant.
>
> If we've already been shot way out to the right, presumably that would give us
> a large real-time lag. If we renice to a lower nice level, wouldn't we want
> to reduce the real-time lag rather than make it constant?

Ah, see but a 1ms real-time lag might be gigantic on weight=15, but
nearly nothing on weight=88761.

1e6 * 1024/15 is massively larger than 1e6 * 1024/88761.

1000000*1024/15 = 68266666
1000000*1024/88761 = 11536





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