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Subject: Re: [OMPI devel] trac ticket 1944 and pending sends
From: Eugene Loh (Eugene.Loh_at_[hidden])
Date: 2009-06-24 10:38:35


Brian Barrett wrote:

> Or go to what I proposed and USE A LINKED LIST! (as I said before,
> not an original idea, but one I think has merit) Then you don't have
> to size the fifo, because there isn't a fifo. Limit the number of
> send fragments any one proc can allocate and the only place memory
> can grow without bound is the OB1 unexpected list. Then use
> SEND_COMPLETE instead of SEND_NORMAL in the collectives without
> barrier semantics (bcast, reduce, gather, scatter) and you
> effectively limit how far ahead any one proc can get to something
> that we can handle, with no performance hit.

I'm still digesting George's mail and trac comments and responses
thereto. Meanwhile, a couple of questions here.

First, I think it'd be helpful if you said a few words about how you
think a linked list should be used here. I can think of a couple of
different ways, and I have questions about each way. Instead of my
enumerating these ways and those questions, how about you just be more
specific? (We used to grow the FIFOs, so sizing them didn't used to be
an issue.)

Second, I'm curious how elaborate of a fix I should be trying for here.
Are we looking for something to fix the problems at hand, or are we
opening the door to rearchitecting a big part of the sm BTL?