So with the aliasing scheme the code for openib would still under
ompi/mca/btl/openib but you could access it with -mca btl ofrc? Ok,
so when an error happens in the openib btl how does it identify
itself? Does it use openib or ofrc? This seems like there could be
some user confusion by adopting the aliasing scheme.
On 11/22/2011 9:22 AM, Jeff Squyres wrote:
Here's what Nathan and I discussed / decided:
1. Nathan shied away from the name "xpmem" in case some other shared memory scheme basically did the same thing as XPMEM (i.e., single copy techniques). (just FYI: xpmem's setup is a little different from KNEM, though, so they didn't merge in KNEM support to vader) Hence, he wanted a neutral name that could apply to xpmem and others. He and Sam have some possible names that could be suitable ("single copy ...something..."; I don't remember offhand).
2. We've long talked about having an MCA component aliasing scheme. Perhaps now is the time to do it. Such a scheme would do two things:
- provide alias names for components. For example, both of the following
would be equivalent:
mpirun --mca btl openib,self ...
mpirun --mca btl ofrc,self ...
- automatically register alias MCA parameters. For example, both of the
following would be equivalent:
mpirun --mca btl_openib_param 1 ...
mpirun --mca btl_ofrc_param 1 ...
This would solve two problems:
2a. Finally be able to rename the "openib" module to something more sensical; "ofrc", perhaps? ("ofrc" = OpenFabrics reliable connected transport, as opposed to the existing "ofud" = OpenFabrics unreliable datagram transport BTL).
2b. Rename vader to be xpmem, because it only supports xpmem at the moment. If that component is expanded in the future to support other similar single-copy schemes, it can be renamed to some neutral name and have "xpmem" as an alias.
Nathan agreed to look into a module aliasing scheme / vader->xpmem rename after he works the hide-OB1/BTL-descriptor-lengths issue that was previously discussed on the list. This will likely be in early/mid December.
On Nov 17, 2011, at 8:11 AM, Jeff Squyres wrote:
After having to explain to someone at SC for the umpteenth time this week that the "vader" BTL uses the XPMEM transport under the covers, I'd like to put forth an appeal to rename the "vader" BTL to be "xpmem."
Here's my rationale for why:
1. Although we have a history of Star Wars-related names, the "ob1" and "r2" components got their names because they're mainly algorithms that have no obvious name that describes what they do.
2. All other components that tie into some back-end system are named reflecting the back-end system (e.g., tcp, mx, portals, ...etc.). "openib" is the weakest example, but we all know that it was named way back when OFED was named "OpenIB", and the name has kinda stuck.
3. The BTL name "xpmem" follows the law of least astonishment from the user's perspective.
4. Cute names rarely seem so after 6 months.
I'll even volunteer to do the work to rename it (a bunch of file moves and global search-and-replaces).
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