Quoting Ankit Navik (2018-12-11 12:14:17) > drm/i915: Context aware user agnostic EU/Slice/Sub-slice control within kernel > > Current GPU configuration code for i915 does not allow us to change > EU/Slice/Sub-slice configuration dynamically. Its done only once while context > is created. > > While particular graphics application is running, if we examine the command > requests from user space, we observe that command density is not consistent. > It means there is scope to change the graphics configuration dynamically even > while context is running actively. This patch series proposes the solution to > find the active pending load for all active context at given time and based on > that, dynamically perform graphics configuration for each context. > > We use a hr (high resolution) timer with i915 driver in kernel to get a > callback every few milliseconds (this timer value can be configured through > debugfs, default is '0' indicating timer is in disabled state i.e. original > system without any intervention).In the timer callback, we examine pending > commands for a context in the queue, essentially, we intercept them before > they are executed by GPU and we update context with required number of EUs. > > Two questions, how did we arrive at right timer value? and what's the right > number of EUs? For the prior one, empirical data to achieve best performance > in least power was considered. For the later one, we roughly categorized > number > of EUs logically based on platform. Now we compare number of pending commands > with a particular threshold and then set number of EUs accordingly with update > context. That threshold is also based on experiments & findings. If GPU is > able > to catch up with CPU, typically there are no pending commands, the EU config > would remain unchanged there. In case there are more pending commands we > reprogram context with higher number of EUs. Please note, here we are changing > EUs even while context is running by examining pending commands every 'x' > milliseconds.
On the overall strategy. This will be unsuitable to be merged as a debugfs interface. So is the idea to evolve into a sysfs interface? As this seems to require tuning for each specific workload, I don't think that would scale too well if you consider a desktop distro? Also, there's the patch series to to enable/disable subslices with VME hardware (the other dynamic slice shutdown/SSEU series) depending on the type of load being run. Certain workloads would hang the system if they're executed with full subslice configuration. In that light, it would make more sense if the applications would be the ones reporting their optimal running configuration. > > With this solution in place, on KBL-GT3 + Android we saw following pnp > benefits, power numbers mentioned here are system power. > > App /KPI | % Power | > | Benefit | > | (mW) | > ---------------------------------| > 3D Mark (Ice storm) | 2.30% | > TRex On screen | 2.49% | > TRex Off screen | 1.32% | > ManhattanOn screen | 3.11% | > Manhattan Off screen | 0.89% | > AnTuTu 6.1.4 | 3.42% | > SynMark2 | 1.70% | Just to verify, these numbers are true while there's no negative effect on the benchmark scores? Regards, Joonas > Note - For KBL (GEN9) we cannot control at sub-slice level, it was always a > constraint. > We always controlled number of EUs rather than sub-slices/slices. > We have also observed GPU core residencies improves by 1.03%. > > Praveen Diwakar (4): > drm/i915: Get active pending request for given context > drm/i915: Update render power clock state configuration for given > context > drm/i915: set optimum eu/slice/sub-slice configuration based on load > type > drm/i915: Predictive governor to control eu/slice/subslice > > drivers/gpu/drm/i915/i915_debugfs.c | 90 > +++++++++++++++++++++++++++++++- > drivers/gpu/drm/i915/i915_drv.c | 4 ++ > drivers/gpu/drm/i915/i915_drv.h | 9 ++++ > drivers/gpu/drm/i915/i915_gem_context.c | 23 ++++++++ > drivers/gpu/drm/i915/i915_gem_context.h | 39 ++++++++++++++ > drivers/gpu/drm/i915/i915_request.c | 2 + > drivers/gpu/drm/i915/intel_device_info.c | 47 ++++++++++++++++- > drivers/gpu/drm/i915/intel_lrc.c | 16 +++++- > 8 files changed, 226 insertions(+), 4 deletions(-) > > -- > 2.7.4 > > _______________________________________________ > Intel-gfx mailing list > Intel-gfx@lists.freedesktop.org > https://lists.freedesktop.org/mailman/listinfo/intel-gfx _______________________________________________ Intel-gfx mailing list Intel-gfx@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/intel-gfx
