Re: 4.3 group scheduling regression

[Peter Zijlstra]

On Tue, Oct 13, 2015 at 03:55:17AM +0800, Yuyang Du wrote:

> I think maybe the real disease is the tg->load_avg is not updated in time.
> I.e., it is after migrate, the source cfs_rq does not decrease its contribution
> to the parent's tg->load_avg fast enough.

No, using the load_avg for shares calculation seems wrong; that would
mean we'd first have to ramp up the avg before you react.

You want to react quickly to actual load changes, esp. going up.

We use the avg to guess the global group load, since that's the best
compromise we have, but locally it doesn't make sense to use the avg if
we have the actual values.
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