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Subject: Re: [OMPI devel] Memory hooks change testing
From: Brian W. Barrett (brbarret_at_[hidden])
Date: 2008-06-11 17:50:26

Brad unfortunately figured out I had done something to annoy the gods of
mercurial and the repository below didn't contain all the changes
advertised (and in fact didn't work). I've since rebuilt the repository
and verified it works now. I'd recommend deleting your existing clones of
the repository below and starting over.

Sorry about that,


On Wed, 11 Jun 2008, 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.
> 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