Quoting Matthew Auld (2020-11-30 17:17:16) > On 27/11/2020 13:55, Chris Wilson wrote: > > Quoting Matthew Auld (2020-11-27 12:06:40) > >> From: Michel Thierry <michel.thierry@xxxxxxxxx> > > > > Rationale goes here. > > > > Is this wise? HWSP is very frequently read by the CPU, and expected to > > be cached on the CPU. > > > > What do the performance profiles indicate? > > Do you have a recommendation for an existing selftest or IGT to help > measure this? > > Also are you suggesting moving this to system memory, or just using a > different mapping type, if it's placed in local memory? Or maybe try > both? Although I'm pretty sceptical about !wc for local memory. A lot of worries go out of the window if this can be in system memory and snooped. For measuring, I suspect there is a lot of chaff that needs to be removed before individual microbenchmarks like perf/request discern any difference; although that would be a starting point. We do a lot of completion checking during execlists interrupt processing, and there we (cpu profiles at least) are sensitive to uncached reads. We can trivially construct a benchmark that only shows the impact of the WC reads; but the point where I think we would first notice from userspace is client wakeup latency scaling: benchmarks/gem_latency, which was once a point of major concern. Nowadays, we can couple that with a second concern about inducing system latency from interrupt processing time. -Chris _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
