On Wed, Mar 15, 2017 at 07:47:20PM +0000, Tvrtko Ursulin wrote: > > On 15/03/2017 14:01, Chris Wilson wrote: > >Check that signaled bit on the request->fence before acquiring a > > "is not set" ^ > > Or "Check that the request has not been signalled before.." ? > > >reference to the request for signaling later in the interrupt handler. > > > >Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> > >Cc: Mika Kuoppala <mika.kuoppala@xxxxxxxxx> > >Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx> > >--- > > drivers/gpu/drm/i915/i915_irq.c | 4 +++- > > 1 file changed, 3 insertions(+), 1 deletion(-) > > > >diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c > >index 31f0d7c8992f..e646c4eba65d 100644 > >--- a/drivers/gpu/drm/i915/i915_irq.c > >+++ b/drivers/gpu/drm/i915/i915_irq.c > >@@ -1056,7 +1056,9 @@ static void notify_ring(struct intel_engine_cs *engine) > > * and many waiters. > > */ > > if (i915_seqno_passed(intel_engine_get_seqno(engine), > >- wait->seqno)) > >+ wait->seqno) && > >+ !test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, > >+ &wait->request->fence.flags)) > > rq = i915_gem_request_get(wait->request); > > > > wake_up_process(wait->tsk); > > > > Is this just to optimize things slightly? Does it happen > sufficiently often for it to be worth it? Even once would be enough. An unlocked read of fence.flags is much cheaper than the locked get/put we go through otherwise. Even if the check is a dud, the load of the cacheline prior to us making it exclusive is "free". I'm mostly thinking about the situations where we have pile of bare breadcrumbs where we may very well get interrupts faster than we can get rid of the intel_wait. Or perhaps a mythical slow device. -Chris -- Chris Wilson, Intel Open Source Technology Centre _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/intel-gfx
