[Beowulf] 1.2 us IB latency?

[greg.lindahl at qlogic.com]

On Tue, Mar 27, 2007 at 09:28:53AM -0700, Greg Lindahl wrote:
> On Mon, Mar 26, 2007 at 06:54:58PM -0400, Mark Hahn wrote:
> 
> > or is this an example of message aggregation?
> 
> The message aggregation number is said to be run with MVAPICH 0.9.9;
> message aggregation is in that version, and can't be disabled.

To correct myself: there are 2 implementations of coalescing in
MVAPICH floating around; one was checked into OFED and can't be
disabled, but the one in MVAPICH mainline can be disabled with:

VIADEV_USE_COALESCE=0

So, I encourage everyone to run with and without coalescing and report
back as to whether your app gets any benefit or not.

-- greg