On Wed, Oct 02, 2013 at 03:20:23PM -0700, Jesse Barnes wrote: > On Wed, 2 Oct 2013 15:18:20 -0700 > Jesse Barnes <jbarnes@xxxxxxxxxxxxxxxx> wrote: > > > On Wed, 2 Oct 2013 22:57:41 +0100 > > Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> wrote: > > > No, that is a factor I had not considered. I had been concerned about > > > monitoring latency whilst minimising frequency and using the power gauge > > > as the ultimate measure of success. One thing that is apparent with ivb, > > > is that the power gauge (at least) is dependent upon workload. That is > > > you can set high frequencies, but if the ring is idle (but not in rc6) > > > then it consumes relatively little power. (That still may be 1W on the > > > big GPUs, but it does mean that at low frequencies there is not a lot of > > > difference between rc6 on/off, a few 10s of mW, and we are concerned > > > with a window of about 10ms.) I suspect the difference is likely to be > > > in the noise for an idle desktop workload and would only really show > > > itself in a synthetic benchmark. > > > > Hm are you sure about that? It doesn't match the last measurements I > > had from a long time ago... until RC6 kicked in the GPU burned quite a > > bit (several Watts). > > > > If you're correct though, then I agree, this is quibbling over crumbs, > > so not worth modifying. > > Oh and the other thing that comes to mind is platform power. Even if > RC6 vs no RC6 at low freq is minimally different, entering RC6 allows > the platform to go into a deep sleep state if the CPUs are also idle. > So race to idle as efficiently as possible is probably still the right > answer. Right, I'm basing my judgement purely on the energy msr, I have no idea how that actually relates to instantaneous power consumption from the battery/mains. I only hope the correlation is good (because that msr is so convenient to measure and record in realtime). I've been deferring to Mengmeng for system power measurements - its about time I actually started measuring those for myself. -Chris -- Chris Wilson, Intel Open Source Technology Centre _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/intel-gfx
