Brian is referring to the "rdma" onesided component (OMPI osd
framework) that directly invokes the BTL functions (vs. using the PML
send/receive functions). The osd matching is quite different than
pt2pt matching.
His concern is that that model continues to work -- e.g., if the rdma
osd component sends a message through a BTL that the other side not
try to interpret and match it as a pt2pt message. Hence, the BTL
would need to learn some new things; e.g., that it can match some
(pml) messages but not all (rdma/osd), or perhaps it would need to
learn about rdma/osd matching as well, or ...(something else)...
IIRC, rdma/osd is the only other non-PML component that sends directly
through the BTLs today. But that may change; I know that there are
some who are working on various optimizations that may use the BTLs
underneath (I don't want to cite them on a public list; this is
unpublished research work at this point).
On Jan 21, 2009, at 1:22 AM, Eugene Loh wrote:
Brian Barrett wrote:
I unfortunately don't have time to look in depth at the patch. But
my concern is that currently (today, not at some made up time in
the future, maybe), we use the BTLs for more than just MPI point-
to- point. The rdma one-sided component (which was added for 1.3
and hopefully will be the default for 1.4) sends messages directly
over the btls. It would be interesting to know how that is handled.
I'm not sure I understand what you're saying.
Does it help to point out that existing BTL routines don't change?
The existing sendi is just a function that, if available, can be
used, where appropriate, to send "immediately". Similarly for the
proposed recvi. No existing BTL functionality is removed. Just
new, optional functions added for whoever wants to (and can) use them.
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Jeff Squyres
Cisco Systems
