Quoting Mika Kuoppala (2018-05-07 09:54:27) > Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> writes: > > > Quoting Mika Kuoppala (2018-05-07 09:34:24) > >> Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> writes: > >> > >> > We rely on ksoftirqd to run in a timely fashion in order to drain the > >> > execlists queue. Quite frequently, it does not. In some cases we may see > >> > latencies of over 200ms triggering our idle timeouts and forcing us to > >> > declare the driver wedged! > >> > > >> > Thus we can speed up idle detection by bypassing ksoftirqd in these > >> > cases and flush our tasklet to confirm if we are indeed still waiting > >> > for the ELSP to drain. > >> > > >> > v2: Put the execlists.first check back; it is required for handling > >> > reset! > >> > > >> > References: https://bugs.freedesktop.org/show_bug.cgi?id=106373 > >> > Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> > >> > Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx> > >> > Cc: Mika Kuoppala <mika.kuoppala@xxxxxxxxxxxxxxx> > >> > --- > >> > drivers/gpu/drm/i915/intel_engine_cs.c | 15 ++++++++++++--- > >> > 1 file changed, 12 insertions(+), 3 deletions(-) > >> > > >> > diff --git a/drivers/gpu/drm/i915/intel_engine_cs.c b/drivers/gpu/drm/i915/intel_engine_cs.c > >> > index 70325e0824e3..a3111511ea1d 100644 > >> > --- a/drivers/gpu/drm/i915/intel_engine_cs.c > >> > +++ b/drivers/gpu/drm/i915/intel_engine_cs.c > >> > @@ -945,10 +945,19 @@ bool intel_engine_is_idle(struct intel_engine_cs *engine) > >> > return true; > >> > > >> > /* Waiting to drain ELSP? */ > >> > - if (READ_ONCE(engine->execlists.active)) > >> > - return false; > >> > + if (READ_ONCE(engine->execlists.active)) { > >> > + struct intel_engine_execlists *execlists = &engine->execlists; > >> > + > >> > + if (tasklet_trylock(&execlists->tasklet)) { > >> > >> Now that we have the lock, sample active again to catch > >> the late tasklet run and skip running if so? > > > > It becomes a nop in the submission tasklet, it's not dangerous. So it > > comes down to what looks less of a wart! > > The nice side effect of this kick is that now the hangcheck also won't > fall a victim. > > Should we have a test which adds random and long tasklet delays? We do, it's called userspace :) We stumbled across a good way of using a RT hog to delay ksoftirqd arbitrarily; it just has the requirement of forcing the tasklet onto the ksoftirqd for the same cpu... -Chris _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/intel-gfx
