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Subject: Re: [hwloc-devel] [hwloc-svn] svn:hwloc r1333
From: Jeff Squyres (jsquyres_at_[hidden])
Date: 2009-11-12 11:28:32


One thing to not forget is that some (many?) applications don't care a
whit about portability to other OS's. You view feature X as a
portability horror; they view it as a feature.

Hence, they may actually *want* to take advantage of the ability to
pin a specific thread (that is not the current thread).

On Nov 11, 2009, at 4:03 PM, Samuel Thibault wrote:

> Brice Goglin, le Thu 12 Nov 2009 00:31:48 +0100, a écrit :
> > The problem is that our hwloc/Linux does not implement
> > set_proc_cpubind() so far.
>
> But it can implement one that assumes that the target process is
> singlethreaded, i.e. in hwloc_set_proc_cpubind distinguish between
> HWLOC_CPUBIND_PROCESS being set or not, or by just passing the policy
> flag as such to OS hooks.
>
> > * document in hwloc.h that it may bind a single thread if the
> > application (wrongly) passes a tid
>
> I'd really rather avoid even mentioning tids in the hwloc
> documentation
> except saying "don't use that, it's not portable, don't even ask,
> you'd
> be horrified".
>
> > * document that hwloc_plpa_sched_setaffinity now works on processes
> > instead of pids and that application should use thread_t and
> > set_thread_cpubind for local threads
>
> Or pass 0 to express "the current thread", which was already valid for
> plpa_sched_setaffinity, and _is_ portable (and should already have
> been
> the only thing that truly portable applications use).
>
> > * maybe return -ENOSYS on Linux if STRICT is given?
>
> I guess you mean return 0 if STRICT is not given, and mean "it's not
> strict because we haven't actually done it for all the threads, or
> even
> not at all"? I'd really rather not lie like this.
>
> Samuel
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> hwloc-devel_at_[hidden]
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>

-- 
Jeff Squyres
jsquyres_at_[hidden]