Re: [Lse-tech] [PATCH] cpusets - big numa cpu and memory placement

Nick Piggin
2004-10-08T10:00:15Z

Erich Focht wrote:
> On Thursday 07 October 2004 20:13, Martin J. Bligh wrote:
>
>>It all just seems like a lot of complexity for a fairly obscure set of
>>requirements for a very limited group of users, to be honest. Some bits
>>(eg partitioning system resources hard in exclusive sets) would seem likely
>>to be used by a much broader audience, and thus are rather more attractive.
>
>
> May I translate the first sentence to: the requirements and usage
> models described by Paul (SGI), Simon (Bull) and myself (NEC) are
> "fairly obscure" and the group of users addressed (those mainly
> running high performance computing (AKA HPC) applications) is "very
> limited"? If this is what you want to say then it's you whose view is
> very limited. Maybe I'm wrong with what you really wanted to say but I
> remember similar arguing from your side when discussing benchmark
> results in the context of the node affine scheduler.
>
> This "very limited group of users" (small part of them listed in
> www.top500.org) is who drives computer technology, processor design,
> network interconnect technology forward since the 1950s. Their
> requirements on the operating system are rather limited and that might
> be the reason why kernel developers tend to ignore them. All that
> counts for HPC is measured in GigaFLOPS or TeraFLOPS, not in elapsed
> seconds for a kernel compile, AIM-7, Spec-SDET or Javabench. The way
> of using these machines IS different from what YOU experience in day
> by day work and Linux is not yet where it should be (though getting
> close). Paul's endurance in this thread is certainly influenced by the
> perspective of having to support soon a 20x512 CPU NUMA cluster at
> NASA...
>
> As a side note: put in the right context your statement on fairly
> obscure requirements for a very limited group of users is a marketing
> argument ... against IBM.
>
> Thanks ;-)
> Erich
>

With all due respect, Linux gets driven as much from the bottom up
as it does from the top down I think. Compared to desktop and small
servers, yes you are obscure :)

My view on it is this, we can do *exclusive* dynamic partitioning
today (we're very close to it - it wouldn't add complexity in the
scheduler to support it). You can also hack up a fair bit of other
functionality with cpu affinity masks.

So with any luck, that will hold you over until everyone working on
this can agree and produce a nice implementation that doesn't add
complexity to the normal case (or can be configured out), and then
pull it into the kernel.