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Subject: Re: [OMPI devel] cpu stride and offset for processor binding
From: Jeff Squyres (jsquyres_at_[hidden])
Date: 2008-02-06 10:05:07


I think the goal was to allow manual specification of this stuff
(E.g., in a text file) even though it could be fairly unwieldy in some
cases (specifying every core in every machine). Then use the
experiences learned from that to work on better syntax / specification
mechanisms.

On Feb 6, 2008, at 3:13 AM, Lenny Verkhovsky wrote:

>
> Hi,
> We are working right now on the new RMAPS component to allow rank
> mapping according to the host : socket : core.
> This component will be general and flexible. You will need to
> support the rankmap file in the command line that looks similar to
> hostfile and the component will do the rest.
>
>
> Regards,
> Lenny.
>
>
>
>
> מאת: devel-bounces_at_[hidden] בשם Pak Lui
> נשלח: ד 06/02/2008 02:01
> אל: devel_at_[hidden]
> נושא: [OMPI devel] cpu stride and offset for processor binding
> Hi all,
>
> I am trying to implement something in the paffinity:solaris that would
> allow me to specify the cpu id with striding (aka in a sequence) when
> selecting which cpu ids to bind. e.g. For a cpu set that looks like
> this: { 0 1 2 3 4 5 6 7 }, and stride is to 2, and offset is to 1
> (which
> means start at pos 1), then ranks will bind to the cpus in the
> following
> order: { 1 3 5 7 2 4 6 0 }. The obvious intent is to take advantage of
> the perf by allocating the ranks in a certain order on multi-core
> systems.
>
> But then we realized this may be implemented elsewhere outside the
> solaris paffinity code. I see something in trac #1023 that may allow
> me
> to specify a cpuid or cores in a range but it doesn't seem to allow me
> specify the cpu id to bind in strides. And with that, rank
> specification
> may seem to be doable, but I may end up entering a long list of cpu
> ids
> in strides manually, if the machine happens to have many cpus. Plus
> another down side is that Solaris doesn't seem to have stable
> interface
> for me to extract out the core/socket information from the kernel. So
> striding might be the only way for me to go for now.
>
> Is there some unspoken feature that's coming down the pipe that may
> allow me to specify cpuids in a sequence, or we already have some
> feature like that that I didn't know about? I look around but I don't
> see anything like this.
>
> Thanks in advance for any comments.
>
> --
>
> - Pak Lui
> pak.lui_at_[hidden]
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-- 
Jeff Squyres
Cisco Systems