Re: Scheduler follow-up: Design target (was [RFC] Scheduler work, part 1)

[Juergen Gross <juergen.gross@ts.fujitsu.com>]

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

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Juergen Gross                 Principal Developer Operating Systems
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