Andrew Gallatin wrote: > Garrett D'Amore wrote: > > I agree with Dana's sentiments here. > > > > I'll add one thing, from my own experience: in my own experience the > > pain and suffering of dealing with scatter/gather is not justified on > > modern systems with ordinary sized ethernet frames. In fact, experience > > You might want to amend this with "on slow networks." For > 10GbE or faster, (and maybe even 1GbE on old, slow hardware) > s/g is definitely worth it. > > Just this morning I doing some tests on a fairly recent 8-way AMD64 > with uperf. Copying rather than mapping roughly doubles CPU > utilization (20% -> 40%) as reported by vmstat for 8 threads sending > on a 10GbE interface (bandwidth is 10GbE line rate regardless).
FWIW, on a T200 with 32 1GHZ CPUS (8 4-thread SMT) using 8 tx/rx queues, and a uperf with 8 threads and using a 1500b MTU I see: LSO off, tx copy off: 3.8Gb/s (30% CPU) LSO off, tx copy on: 4.2Gb/s (32% CPU) LSO on, tx copy off: 9.1Gb/s (18% CPU) LSO on, tx copy on: 6.5Gb/s (23% CPU) So, it seems like 10GbE, copying is almost a wash without LSO, and a pessimization with LSO even on sparc. Drew _______________________________________________ driver-discuss mailing list [email protected] http://mail.opensolaris.org/mailman/listinfo/driver-discuss
