linux-kernel - Re: getting processor numbers

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Message-Id: <20070403195846.d03fe3ec.pj@sgi.com>
Date:	Tue, 3 Apr 2007 19:58:46 -0700
From:	Paul Jackson <pj@....com>
To:	Ulrich Drepper <drepper@...hat.com>
Cc:	akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
	ego@...ibm.com, dipankar@...ibm.com
Subject: Re: getting processor numbers

Ulrich wrote:
> But all this of course does not solve the issue sysconf() has.  In
> sysconf we cannot use sched_getaffinity since all the systems CPUs must
> be reported.

Good point.  Yes, sysconf(_SC_NPROCESSORS_CONF) really needs to continue
returning the number of CPUs online, to maintain compatibility with the
current implementation, and because with a name like that, just about
anything else would be "surprising".

And OpenMPI shouldn't be calling sysconf(_SC_NPROCESSORS_CONF), as it does
not want to know how much hardware is there, but rather how much hardware
it is allowed to use.  Something based on sched_getaffinity() would seem
to be ideal for its purposes.

-- 
                  I won't rest till it's the best ...
                  Programmer, Linux Scalability
                  Paul Jackson <pj@....com> 1.925.600.0401
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