On Fri, Dec 18, 2015 at 02:29:22PM +0000, Chris Wilson wrote: > On Fri, Dec 18, 2015 at 01:51:38PM +0000, Tvrtko Ursulin wrote: > > On 18/12/15 12:28, Chris Wilson wrote: > > >An interesting igt experiement I think would be: > > > > > >thread A, keep queuing batches with just a single MI_STORE_DWORD_IMM *addr > > >thread B, waits on batch from A, reads *addr (asynchronously), measures > > >latency (actual value - expected(batch)) > > > > > >Run for 10s, report min/max/median latency. > > > > > >Repeat for more threads/contexts and more waiters. Ah, that may be the > > >demonstration for the thundering herd I've been looking for! > > > > Hm I'll think about it. > > I'm working on this as I have been trying to get something to measure > the thundering herd issue (I have one benchmark that measures how much > CPU time we steal to handle interrupts, but it is horrible). Remembered that we have timestamp registers. So igt/benchmarks/gem_latency measures the number of engine cycles from the end of a batch to the time the client is woken up (for a variety of producer:consumers). That should be suitable to serve as a basis for measurements. -Chris -- Chris Wilson, Intel Open Source Technology Centre _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/intel-gfx
