Re: [PATCH v3 0/5] Scan for an idle sibling in a single pass

Mel Gorman
2021-01-26T03:07:36Z

On Mon, Jan 25, 2021 at 07:37:55PM +0800, Li, Aubrey wrote:
> > It's interesting that patch 3 would make any difference on x64 given that
> > it's SMT2. The scan depth should have been similar. It's somewhat expected
> > that it will not be a universal win, particularly once the utilisation
> > is high enough to spill over in sched domains (25%, 50%, 75% utilisation
> > being interesting on 4-socket systems). In such cases, double scanning can
> > still show improvements for workloads that idle rapidly like tbench and
> > hackbench even though it's expensive. The extra scanning gives more time
> > for a CPU to go idle enough to be selected which can improve throughput
> > but at the cost of wake-up latency,
>
> aha, sorry for the confusion. Since you and Vincent discussed to drop
> patch3, I just mentioned I tested 5 patches with patch3, not patch3 alone.
>

Ah, that makes more sense.

> >
> > Hopefully v4 can be tested as well which is now just a single scan.
> >
>
> Sure, may I know the baseline of v4?
>

5.11-rc4.

--
Mel Gorman
SUSE Labs