Open MPI logo

Open MPI Development Mailing List Archives

  |   Home   |   Support   |   FAQ   |  

This web mail archive is frozen.

This page is part of a frozen web archive of this mailing list.

You can still navigate around this archive, but know that no new mails have been added to it since July of 2016.

Click here to be taken to the new web archives of this list; it includes all the mails that are in this frozen archive plus all new mails that have been sent to the list since it was migrated to the new archives.

From: Galen Shipman (gshipman_at_[hidden])
Date: 2007-05-11 15:15:40

> As an aside, my personal feeling is that even when running over IB the
> preposting of recvs is worth the small overhead of piggybacking a
> credit
> system on the messages that already cross the wire. If nothing else,
> this avoids adding congestion of RNR-NAKS and the resends they
> trigger.
> Put another way, I favor programming for IB as if it lacked the
> link-level flow control that the current BTL apparently assumes.

We avoid the RNR-NAKS in the Open IB BTL via a credit system.
I would have to review the udapl BTL but I believe it does something
I believe the problem only exists during lazy connection
establishment, when credits are probably initialized to the defaults
on both ends. We should really just set the credits as part of the
handshake (after the receiver has posted the receive buffers).

- Galen

> -Paul
> --
> Paul H. Hargrove PHHargrove_at_[hidden]
> Future Technologies Group
> HPC Research Department Tel: +1-510-495-2352
> Lawrence Berkeley National Laboratory Fax: +1-510-486-6900
> _______________________________________________
> devel mailing list
> devel_at_[hidden]