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Subject: Re: [OMPI devel] cpu stride and offset for processor binding
From: Lenny Verkhovsky (lennyb_at_[hidden])
Date: 2008-02-06 03:13:42



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.










îàú: devel-bounces_at_[hidden] áùí Pak Lui
ðùìç: ã 06/02/2008 02:01
àì: devel_at_[hidden]
ðåùà: [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
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