Quoting r. Roland Dreier <[EMAIL PROTECTED]>: > Subject: Re: Gen2 User verbs usage > > Michael> There currently doesnt seem to exist a way for userspace > Michael> to know when is setting the INLINE flag possible. > > I seem to remember some discussion where we said the inline flag was > just a hint for the low-level driver, so it's always possible to set it.
I'm not against this approach, on principle, what bothers me latency vs cpu utilization tradeoff is involved so the low-level driver may not be the right place to take that decision. There's also the point that for inline you dont need to pass in a valid rkey, so the app may be better off knowing about it. Finally, if its just a hint a separate pass over the s/g list would be needed to calculate the size and check it fits inline, which kind of implies performance penalty. What is your opinion? > Michael> It would seem what we need is another attribute passed to > Michael> create_qp that would specify the max inline buffer size, > Michael> and probably an hca attribute to give the maximum legal > Michael> value for this attribute. > > Do we care enough about this special feature to do this? It seems > Mellanox VAPI worked out OK without that. > > - R. > It may be users are only recently waking to this feature. Latency benefits for small to medium sized messages are significant. -- MST - Michael S. Tsirkin _______________________________________________ openib-general mailing list [email protected] http://openib.org/mailman/listinfo/openib-general To unsubscribe, please visit http://openib.org/mailman/listinfo/openib-general
