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. Propagating a flag through to sync_file is trivial, but not through to the dma_buf->resv. Looks like dma-buf will be without a fast busy query, which I guess in the grand scheme of things (i.e. dma-buf itself is not intended to be used as a fence) is not that important. -Chris -- Chris Wilson, Intel Open Source Technology Centre -- 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
