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SubjectRe: [RFC PATCH v3 00/16] Core scheduling v3
On Wed, 2019-08-07 at 10:10 -0700, Tim Chen wrote:
> On 8/7/19 1:58 AM, Dario Faggioli wrote:
> > Since I see that, in this thread, there are various patches being
> > proposed and discussed... should I rerun my benchmarks with them
> > applied? If yes, which ones? And is there, by any chance, one (or
> > maybe
> > more than one) updated git branch(es)?
> >
> Hi Dario,
Hi Tim!

> Having an extra set of eyes are certainly welcomed.
> I'll give my 2 cents on the issues with v3.
Ok, and thanks a lot for this.

> 1) Unfairness between the sibling threads
> -----------------------------------------
> One sibling thread could be suppressing and force idling
> the sibling thread over proportionally. Resulting in
> the force idled CPU not getting run and stall tasks on
> suppressed CPU.
> [...]
> 2) Not rescheduling forced idled CPU
> ------------------------------------
> The forced idled CPU does not get a chance to re-schedule
> itself, and will stall for a long time even though it
> has eligible tasks to run.
> [...]
> 3) Load balancing between CPU cores
> -----------------------------------
> Say if one CPU core's sibling threads get forced idled
> a lot as it has mostly incompatible tasks between the siblings,
> moving the incompatible load to other cores and pulling
> compatible load to the core could help CPU utilization.
> So just considering the load of a task is not enough during
> load balancing, task compatibility also needs to be considered.
> Peter has put in mechanisms to balance compatible tasks between
> CPU thread siblings, but not across cores.
> [...]
Ok. Yes, as said, I've been trying to follow the thread, but thanks a
lot again for this summary.

As said, I'm about to have numbers for the repo/branch I mentioned.

I was considering whether to also re-run the benchmarking campaign with
some of the patches that floated around within this thread. Now, thanks
to your summary, I have an even clearer picture about which patch does
what, and that is indeed very useful.

I'll see about putting something together. I'm thinking of picking:

And maybe even (part of):

If anyone has ideas or suggestions about whether or not this choice
makes sense, feel free to share. :-)

Also, I only have another week before leaving, so let's see what I
manage to actually run, and then share here, by then.

Thanks and Regards
Dario Faggioli, Ph.D
Virtualization Software Engineer
<<This happens because _I_ choose it to happen!>> (Raistlin Majere)

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