On Fri, Sep 23, 2016 at 07:59:44PM +0200, Christian König wrote: > 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@xxxxxxxxxxxxxxxxxx> > > > > Cc: Sumit Semwal <sumit.semwal@xxxxxxxxxx> > > > > Cc: linux-media@xxxxxxxxxxxxxxx > > > > Cc: dri-devel@xxxxxxxxxxxxxxxxxxxxx > > > > Cc: linaro-mm-sig@xxxxxxxxxxxxxxxx > > > > Reviewed-by: Daniel Vetter <daniel.vetter@xxxxxxxx> > > > 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@xxxxxxx> > > 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@xxxxxxx> > > Reviewed-by: Christian König <christian.koenig@xxxxxxx> > > Reviewed-by: Alex Deucher <alexander.deucher@xxxxxxx> > > Reviewed-By: Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxx> > > Signed-off-by: Sumit Semwal <sumit.semwal@xxxxxxxxxx> > > > > 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. Will you/Zhou take care of this corner case? Just so I can't forget about it ;-) Thanks, Daniel -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
