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Subject: Re: [OMPI devel] Memory hooks change testing
From: Pavel Shamis (Pasha) (pasha_at_[hidden])
Date: 2008-06-11 14:20:47

Brian Barrett wrote:
> Did anyone get a chance to test (or think about testing) this? I'd
> like to commit the changes on Friday evening, if I haven't heard any
> negative feedback.
I will run it tomorrow on my cluster.
> Brian
> On Jun 9, 2008, at 8:56 PM, Brian Barrett wrote:
>> Hi all -
>> Per the RFC I sent out last week, I've implemented a revised
>> behavior of the memory hooks for high speed networks. It's a bit
>> different than the RFC proposed, but still very minor and fairly
>> straight foward.
>> The default is to build ptmalloc2 support, but as an almost complete
>> standalone library. If the user wants to use ptmalloc2, he only has
>> to add -lopenmpi-malloc to his link line. Even when standalone and
>> openmpi-malloc is not linked in, we'll still intercept munmap as
>> it's needed for mallopt (below) and we've never had any trouble with
>> that part of ptmalloc2 (it's easy to intercept).
>> As a *CHANGE* in behavior, if leave_pinned support is turned on and
>> there's no ptmalloc2 support, we will automatically enable mallopt.
>> As a *CHANGE* in behavior, if the user disables mallopt or mallopt
>> is not available and leave pinned is requested, we'll abort. I
>> think these both make sense and are closest to expected behavior,
>> but wanted to point them out. It is possible for the user to
>> disable mallopt and enable leave_pinned, but that will *only* work
>> if there is some other mechanism for intercepting free (basically,
>> it allows a way to ensure your using ptmalloc2 instead of mallopt).
>> There is also a new memory component, mallopt, which only intercepts
>> munmap and exists only to allow users to enable mallopt while not
>> building the ptmalloc2 component at all. Previously, our mallopt
>> support was lacking in that it didn't cover the case where users
>> explicitly called munmap in their applications. Now, it does.
>> The changes are fairly small and can be seen/tested in the HG
>> repository bwb/mem-hooks, URL below. I think this would be a good
>> thing to push to 1.3, as it will solve an ongoing problem on Linux
>> (basically, users getting screwed by our ptmalloc2 implementation).
>> Brian
>> --
>> Brian Barrett
>> Open MPI developer