On Tue, 2017-11-14 at 21:30 +0000, Chris Wilson wrote: > I should have admitted defeat long ago as there has been a rare but > persistent error on Sandybridge where semaphore signaling did not > propagate to the waiter, leading to a GPU hang. > > With the work on fence signaling for v4.9, the impact of using CPU driven > signaling was greatly reduced wrt to the latency of GPU semaphores, > though without logical rings support, the benefit of reordering work to > avoid bubbles is not realised (i.e. as it stands fence signaling is just > a slower, more costly version of HW semaphores; but works more > consistently). As a rough indicator of the difference, > > with semaphores: > Sequential (3 engines, 1 processes): average 5.470us per cycle [expected 4.988us] > > w/o semaphores: > Sequential (3 engines, 1 processes): average 15.771us per cycle [expected 4.923us] > > Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=54226 > Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> > Cc: Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx> > Acked-by: Mika Kuoppala <mika.kuoppala@xxxxxxxxxxxxxxx> Might be worth mentioning that the bug casually has 110 duplicates... Reviewed-by: Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx> Regards, Joonas -- Joonas Lahtinen Open Source Technology Center Intel Corporation _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/intel-gfx
