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Re: [PATCH 0/2] xen: credit2: limit the number of CPUs per runqueue

  • To: Dario Faggioli <dfaggioli@xxxxxxxx>
  • From: George Dunlap <George.Dunlap@xxxxxxxxxx>
  • Date: Fri, 29 May 2020 16:15:35 +0000
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  • Cc: Juergen Gross <jgross@xxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Paul Durrant <paul@xxxxxxx>, Jan Beulich <jbeulich@xxxxxxxx>, Andrew Cooper <Andrew.Cooper3@xxxxxxxxxx>
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  • Thread-topic: [PATCH 0/2] xen: credit2: limit the number of CPUs per runqueue

> On May 29, 2020, at 12:46 PM, Dario Faggioli <dfaggioli@xxxxxxxx> wrote:
> So,
> I felt like providing some additional thoughts about this series, from
> a release point of view (adding Paul).
> Timing is *beyond tight* so if this series, entirely or partly, has any
> chance to go in, it would be through some form of exception, which of
> course comes with some risks, etc.
> I did work hard to submit the full series, because I wanted people to
> be able to see the complete solution. However, I think the series
> itself can be logically split in two parts.
> Basically, if we just consider patches 1 and 4 we will end up, right
> after boot, with a system that has smaller runqueues. They will most
> likely be balanced in terms of how many CPUs each one has, so a good
> setup. This will likely (actual differences seems to depend *quite a
> bit* on the actual workload) be an improvement for very large systems.

Fundamentally, I feel like the reason we have the feature freeze is exactly to 
have to avoid questions like this.  Something very much like patch 4 was posted 
before the last posting date; patches 1-4 received R-b’s before the feature 
freeze.  I think they should probably go in.

The rebalancing patches I’m inclined to say should wait until they’ve had a bit 
more time to be thought about.




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