1. The send path get shorter. The BTL is allowed to return > 0 to specify that the
descriptor was pushed to the networks, and that the memory attached to it is
available again for the upper layer. The MCA_BTL_DES_SEND_ALWAYS_CALLBACK flag
can be used by the PML to force the BTL to always trigger the callback.
Unmodified BTL will continue to work as expected, as they will return OMPI_SUCCESS
which force the PML to have exactly the same behavior as before. Some BTLs have
been modified: self, sm, tcp, mx.
2. Add send immediate interface to BTL.
The idea is to have a mechanism of allowing the BTL to take advantage of
send optimizations such as the ability to deliver data "inline". Some
network APIs such as Portals allow data to be sent using a "thin" event
without packing data into a memory descriptor. This interface change
allows the BTL to use such capabilities and allows for other optimizations
in the future. All existing BTLs except for Portals and sm have this interface
set to NULL.
This commit was SVN r18551.
e361bcb64c