[EMAIL PROTECTED] wrote: > Quoting r. Tom Tucker <[EMAIL PROTECTED]>: >> Subject: RDMA_READ SGE >> >> Roland: >> >> iWARP RNIC's have a different SGE limit for RDMA_READ response then >> they do for other SGE. To support iWARP, we need to add a >> max_read_sge attribute to the ib_device structure. We had originally >> mapped this to max_sge_rd, but someone pointed out that this is not >> for RDMA_READ in general, but for RDMA_READ_ATOMIC in particular. >> >> In any event, we need to add this value to the ib_verbs.h structure >> so that ULP know how to limit sge for the RDMA_READ sink. >> >> Do you want me to submit a patch on top of Steve's, or do you want me >> to wait until you've got the git tree built? >> >> Thanks, >> Tom > > Actually, Mellanox devices also have different SGE limits > depending on the operation kinds and QP types. > So far the approach there has been that the device should > report one value for the best case result. > > Practically I don't see reporting the exact values as a > priority - I think applications really can figure this out > easier by attempting operating with relevant parameters and > fallback to smaller values on failure. > > But assuming that applications really need this information - > it seems we really should generalize this - maybe make the > device provide a function mapping QP attributes and operation > kinds to the max set of values allowed?
That was the consensus in RNIC-PI, report as many distinct values as required so that the chances that a device would end up under- reporting any capability would be minimal. For iWARP, the RDMA Read SGE length is fairly critical, though. It is almost always exactly one. Having to report that you only support a single SGE when in fact *only* RDMA Reads have that restriction would be misleading the application a lot. The other distinctions don't tend to be a severe. _______________________________________________ openib-general mailing list [email protected] http://openib.org/mailman/listinfo/openib-general To unsubscribe, please visit http://openib.org/mailman/listinfo/openib-general
