Hi, > -----Original Message----- > From: Daniel Vetter [mailto:daniel.vetter@xxxxxxxx] On Behalf Of Daniel Vetter > Sent: Wednesday, April 08, 2015 2:40 PM > To: Chris Wilson > Cc: intel-gfx@xxxxxxxxxxxxxxxxxxxxx; Daniel Vetter; Tvrtko Ursulin; Tamminen, > Eero T; Rantala, Valtteri > Subject: Re: [PATCH 17/70] drm/i915: Optimistically spin for the request > completion > > On Tue, Apr 07, 2015 at 04:20:41PM +0100, Chris Wilson wrote: > > This provides a nice boost to mesa in swap bound scenarios (as mesa > > throttles itself to the previous frame and given the scenario that > > will complete shortly). It will also provide a good boost to systems > > running with semaphores disabled and so frequently waiting on the GPU > > as it switches rings. In the most favourable of microbenchmarks, this > > can increase performance by around 15% - though in practice > > improvements will be marginal and rarely noticeable. > > > > v2: Account for user timeouts > > v3: Limit the spinning to a single jiffie (~1us) at most. On an > > otherwise idle system, there is no scheduler contention and so without > > a limit we would spin until the GPU is ready. > > v4: Drop forcewake - the lazy coherent access doesn't require it, and > > we have no reason to believe that the forcewake itself improves seqno > > coherency - it only adds delay. > > > > Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> > > Cc: Daniel Vetter <daniel.vetter@xxxxxxxx> > > Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxxxxxxxx> > > Cc: Eero Tamminen <eero.t.tamminen@xxxxxxxxx> > > Cc: "Rantala, Valtteri" <valtteri.rantala@xxxxxxxxx> > > Eero/Valtterri, do you have perf data for this one? > [Rantala, Valtteri] I have issues with applying this patch to latest night, have to check that out. Can you provide Git/branch that I could use? -- Valtteri > Thanks, Daniel > > > --- > > drivers/gpu/drm/i915/i915_gem.c | 44 > > +++++++++++++++++++++++++++++++++++------ > > 1 file changed, 38 insertions(+), 6 deletions(-) > > > > diff --git a/drivers/gpu/drm/i915/i915_gem.c > > b/drivers/gpu/drm/i915/i915_gem.c index c7d9ee2f708a..47650327204e > > 100644 > > --- a/drivers/gpu/drm/i915/i915_gem.c > > +++ b/drivers/gpu/drm/i915/i915_gem.c > > @@ -1181,6 +1181,29 @@ static bool missed_irq(struct drm_i915_private > *dev_priv, > > return test_bit(ring->id, &dev_priv->gpu_error.missed_irq_rings); > > } > > > > +static int __i915_spin_request(struct drm_i915_gem_request *rq) { > > + unsigned long timeout; > > + > > + if (i915_gem_request_get_ring(rq)->irq_refcount) > > + return -EBUSY; > > + > > + timeout = jiffies + 1; > > + while (!need_resched()) { > > + if (i915_gem_request_completed(rq, true)) > > + return 0; > > + > > + if (time_after_eq(jiffies, timeout)) > > + break; > > + > > + cpu_relax_lowlatency(); > > + } > > + if (i915_gem_request_completed(rq, false)) > > + return 0; > > + > > + return -EAGAIN; > > +} > > + > > /** > > * __i915_wait_request - wait until execution of request has finished > > * @req: duh! > > @@ -1225,12 +1248,20 @@ int __i915_wait_request(struct > drm_i915_gem_request *req, > > if (INTEL_INFO(dev)->gen >= 6) > > gen6_rps_boost(dev_priv, file_priv); > > > > - if (!irq_test_in_progress && WARN_ON(!ring->irq_get(ring))) > > - return -ENODEV; > > - > > /* Record current time in case interrupted by signal, or wedged > */ > > trace_i915_gem_request_wait_begin(req); > > before = ktime_get_raw_ns(); > > + > > + /* Optimistic spin for the next jiffie before touching IRQs */ > > + ret = __i915_spin_request(req); > > + if (ret == 0) > > + goto out; > > + > > + if (!irq_test_in_progress && WARN_ON(!ring->irq_get(ring))) { > > + ret = -ENODEV; > > + goto out; > > + } > > + > > for (;;) { > > struct timer_list timer; > > > > @@ -1279,14 +1310,15 @@ int __i915_wait_request(struct > drm_i915_gem_request *req, > > destroy_timer_on_stack(&timer); > > } > > } > > - now = ktime_get_raw_ns(); > > - trace_i915_gem_request_wait_end(req); > > - > > if (!irq_test_in_progress) > > ring->irq_put(ring); > > > > finish_wait(&ring->irq_queue, &wait); > > > > +out: > > + now = ktime_get_raw_ns(); > > + trace_i915_gem_request_wait_end(req); > > + > > if (timeout) { > > s64 tres = *timeout - (now - before); > > > > -- > > 2.1.4 > > > > -- > Daniel Vetter > Software Engineer, Intel Corporation > http://blog.ffwll.ch --------------------------------------------------------------------- Intel Finland Oy Registered Address: PL 281, 00181 Helsinki Business Identity Code: 0357606 - 4 Domiciled in Helsinki This e-mail and any attachments may contain confidential material for the sole use of the intended recipient(s). Any review or distribution by others is strictly prohibited. If you are not the intended recipient, please contact the sender and delete all copies. _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/intel-gfx
