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Re: [Xen-devel] Scheduler follow-up: Design target (was [RFC] Scheduler

To: George Dunlap <George.Dunlap@xxxxxxxxxxxxx>
Subject: Re: [Xen-devel] Scheduler follow-up: Design target (was [RFC] Scheduler work, part 1)
From: Juergen Gross <juergen.gross@xxxxxxxxxxxxxx>
Date: Fri, 17 Apr 2009 14:11:32 +0200
Cc: Ian Pratt <Ian.Pratt@xxxxxxxxxxxxx>, "Tian, Kevin" <kevin.tian@xxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>, Jeremy Fitzhardinge <jeremy@xxxxxxxx>
Delivery-date: Fri, 17 Apr 2009 05:12:01 -0700
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George Dunlap wrote:
> * [Jeremy] Is that forward-looking enough?  That hardware is currently
> available; what's going to be commonplace in 2-3 years?
> I think we need to distinguish between "works optimally" and "works
> well".  Obviously we want the design to be scalable, and we don't want
> to have to do a major revision in a year because 16 logical cpus works
> well but 32 tanks.  And it may be a good idea to "lead" the target, so
> that when we actually ship something it will be right on, rather than
> 6 months behind.

This problem might be less critical if cpupools are supported. On really
large systems it would be possible to limit the number of logical cpus
for a scheduler.

> Still, in 2-3 years, will the vast majority of servers have 32 logical
> cpus, or still only 16 or less?

I think Nehalem-EX will have 16 on one socket (8 cores with 2 HT each).
With 4 sockets this would sum up to 64.

> * [Kevin Tian] How about VM number in total you'd like to support?
> Good question.  I'll do some research for how many VMs a virtual
> desktop system might want to support.
> For servers, I think a reasonable design space would be between 1 VM
> every 3 cores (for a few extremely high-load servers) to 8 VMs every
> core (for highly aggregated servers).  I suppose server farms may want
> more.
> Does anyone else have any thoughts on this subject -- either
> suggestions for different numbers, or other use cases they want
> considered?

For our BS2000 servers we would really appreciate support of cpupools :-)
Or as an alternative correct handling of weights with cpu-pinning.

Another question: do you plan to replace the current credit scheduler or will
the new scheduler be another alternative to credit and sedf?


Juergen Gross                 Principal Developer Operating Systems
TSP ES&S SWE OS6                       Telephone: +49 (0) 89 636 47950
Fujitsu Technolgy Solutions               e-mail: juergen.gross@xxxxxxxxxxxxxx
Otto-Hahn-Ring 6                        Internet: ts.fujitsu.com
D-81739 Muenchen                 Company details: ts.fujitsu.com/imprint.html

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