Am 23.09.2016 um 17:20 schrieb Chris Wilson: > On Fri, Sep 23, 2016 at 03:50:44PM +0200, Daniel Vetter wrote: >> On Mon, Aug 29, 2016 at 08:08:34AM +0100, Chris Wilson wrote: >>> Currently we install a callback for performing poll on a dma-buf, >>> irrespective of the timeout. This involves taking a spinlock, as well as >>> unnecessary work, and greatly reduces scaling of poll(.timeout=0) across >>> multiple threads. >>> >>> We can query whether the poll will block prior to installing the >>> callback to make the busy-query fast. >>> >>> Single thread: 60% faster >>> 8 threads on 4 (+4 HT) cores: 600% faster >>> >>> Still not quite the perfect scaling we get with a native busy ioctl, but >>> poll(dmabuf) is faster due to the quicker lookup of the object and >>> avoiding drm_ioctl(). >>> >>> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk> >>> Cc: Sumit Semwal <sumit.semwal at linaro.org> >>> Cc: linux-media at vger.kernel.org >>> Cc: dri-devel at lists.freedesktop.org >>> Cc: linaro-mm-sig at lists.linaro.org >>> Reviewed-by: Daniel Vetter <daniel.vetter at ffwll.ch> >> Need to strike the r-b here, since Christian König pointed out that >> objects won't magically switch signalling on. > Oh, it also means that > > commit fb8b7d2b9d80e1e71f379e57355936bd2b024be9 > Author: Jammy Zhou <Jammy.Zhou at amd.com> > Date: Wed Jan 21 18:35:47 2015 +0800 > > reservation: wait only with non-zero timeout specified (v3) > > When the timeout value passed to reservation_object_wait_timeout_rcu > is zero, no wait should be done if the fences are not signaled. > > Return '1' for idle and '0' for busy if the specified timeout is '0' > to keep consistent with the case of non-zero timeout. > > v2: call fence_put if not signaled in the case of timeout==0 > > v3: switch to reservation_object_test_signaled_rcu > > Signed-off-by: Jammy Zhou <Jammy.Zhou at amd.com> > Reviewed-by: Christian König <christian.koenig at amd.com> > Reviewed-by: Alex Deucher <alexander.deucher at amd.com> > Reviewed-By: Maarten Lankhorst <maarten.lankhorst at canonical.com> > Signed-off-by: Sumit Semwal <sumit.semwal at linaro.org> > > is wrong. And reservation_object_test_signaled_rcu() is unreliable.
Ups indeed, that patch is wrong as well. I suggest that we just enable the signaling in this case as well. Regards, Christian. > -Chris >
