Quoting Mika Kuoppala (2020-01-14 15:12:03) > Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> writes: > > > Allow the sysadmin to specify whether we should prevent the CPU from > > entering higher C-states while waiting for the CPU, in order to reduce > > s/higher/deeper > s/CPU/GPU > > > the latency of request completions and so speed up client continuations. > > > > The target dma latency can be adjusted per-engine using, > > > > /sys/class/drm/card?/engine/*/dma_latency_ns > > > > (For waiting on a virtual engine, the underlying physical engine is used > > for the wait once the request is active, so set all the physical engines > > in the virtual set to the same target dma latency.) > > > > Note that in most cases, the ratelimiting step does not appear to the > > interrupt latency per se, but secondary effects of avoiding additional > > memory latencies while active. > > > > Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> > > Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxxxxxxxx> > > Cc: Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx> > > Cc: Eero Tamminen <eero.t.tamminen@xxxxxxxxx> > > Cc: Francisco Jerez <currojerez@xxxxxxxxxx> > > Cc: Mika Kuoppala <mika.kuoppala@xxxxxxxxxxxxxxx> > > Cc: Dmitry Rogozhkin <dmitry.v.rogozhkin@xxxxxxxxx> > > --- > > drivers/gpu/drm/i915/Kconfig.profile | 14 ++++++ > > drivers/gpu/drm/i915/gt/intel_breadcrumbs.c | 48 ++++++++++++++++++++ > > drivers/gpu/drm/i915/gt/intel_engine_cs.c | 2 + > > drivers/gpu/drm/i915/gt/intel_engine_sysfs.c | 31 +++++++++++++ > > drivers/gpu/drm/i915/gt/intel_engine_types.h | 9 ++++ > > 5 files changed, 104 insertions(+) > > > > diff --git a/drivers/gpu/drm/i915/Kconfig.profile b/drivers/gpu/drm/i915/Kconfig.profile > > index ba8767fc0d6e..a956f1bb9caf 100644 > > --- a/drivers/gpu/drm/i915/Kconfig.profile > > +++ b/drivers/gpu/drm/i915/Kconfig.profile > > @@ -12,6 +12,20 @@ config DRM_I915_USERFAULT_AUTOSUSPEND > > May be 0 to disable the extra delay and solely use the device level > > runtime pm autosuspend delay tunable. > > > > +config DRM_I915_DMA_LATENCY > > + int "Target CPU-DMA latency while waiting on active requests (ns)" > > + default -1 # nanoseconds > > + help > > + Specify a target latency for DMA wakeup, see /dev/cpu_dma_latency, > > + used while the CPU is waiting for GPU results. > > + > > + This is adjustable via > > + /sys/class/drm/card?/engine/*/dma_latency_ns > > + > > + May be -1 to prevent specifying a target wakeup and let the CPU > > + enter powersaving while waiting. Conversely, 0 may be used to > > + prevent the CPU from entering any C-states while waiting. > > Who will be the target group to touch this tunable if it is default off? It dramatically improves our fake transcode benchmarks, so I think there will be those who find it useful and willing to pay the joules. -Chris _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/intel-gfx
