Re: [RESEND PATCH 2/3 v5] sched: Rewrite per entity runnable load average tracking

[Yuyang Du]

On Tue, Oct 21, 2014 at 04:54:35PM +0200, Peter Zijlstra wrote:
> 
> In the thread here: lkml.kernel.org/r/1409094682.29189.23.camel@j-VirtualBox
> there are concerns about the error bounds of such constructs. We can
> basically 'leak' nr_cpus * threshold, which is potentially a very large
> number.
> 
> Do we want to introduce the force updated to combat this?

So introduce a force update here like:

+static inline void update_tg_load_avg(struct cfs_rq *cfs_rq, int force)
...
+	if (force || abs(delta) > cfs_rq->tg_load_avg_contrib / 64) {

That is good. In general, I have been lacking a theory about what threshold
should be concerning overhead vs. accuracy. But I think adding a force here
provides us an option to better comply with the theory if we have it.

Thanks,
Yuyang
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