Hi Abhinav, Could you provide more information about the testing scenario? Was it MFC + FIMC, or MFC + DRM, or MFC + FIMC + DRM, or other?
According to the DMABUF spec map/unmap calls should be done just before a buffer is accessed by HW. In case of vb2, dma_buf_map_attachment is called just after passing the buffer to the vb2 queue. IMO, it is too early. The mapping call should be moved to __enqueue_in_driver function one day.
As I understand the DMABUF assumptions, it is exporter code to be responsible for caching mappings for dmabuf attachments.
I applied some caching policy in vb2-dma-contig exporter. The similar treat should be ported to the DRM code. I am waiting for opinions about this solution.
Regards, Tomasz Stanislawski
On 06/14/2012 06:48 PM, Abhinav Kochhar wrote:
Hi Tomasz,Sumit,
We have been doing performance analysis for video playback scenarios. Could get significant improvement in FPS (33% or 8~10 fps) for full HD resolution when the map/unmap sequence is not called. This is a considerable improvement in performance and would be helpful to have some logical way using e.g. "dmabuf hint" to avoid what looks like a bottleneck (map/unmap sequence).
For your reference I have I have copied the changes below. Please note this is a change for verification into the vb2 core to add an additional condition check for avoiding the calls to map/unmap if the buffer has been already mapped once.
diff --git a/drivers/media/video/videobuf2-core.c b/drivers/media/video/videobuf2-core.c index 1e0917d..e48a7fc 100644 --- a/drivers/media/video/videobuf2-core.c +++ b/drivers/media/video/videobuf2-core.c @@ -1098,12 +1098,15 @@ static int __qbuf_dmabuf(struct vb2_buffer *vb, const struct v4l2_buffer *b) * really we want to do this just before the DMA, not while queueing * the buffer(s).. */
- for (plane = 0; plane < vb->num_planes; ++plane) {
ret = call_memop(q, map_dmabuf, vb->planes[plane].mem_priv);if (ret) {dprintk(1, "qbuf: failed mapping dmabuf ""memory for plane %d\n", plane);goto err;
if( vb->planes[plane].dbuf_mapped != 1) {ret = call_memop(q, map_dmabuf, vb->planes[plane].mem_priv);if (ret) {dprintk(1, "qbuf: failed mapping dmabuf ""memory for plane %d\n", plane);goto err;}@@ -1525,14 +1528,6 @@ int vb2_dqbuf(struct vb2_queue *q, struct v4l2_buffer *b, bool nonblocking) * really we want to do this just after DMA, not when the * buffer is dequeued.. */
if (q->memory == V4L2_MEMORY_DMABUF) {
unsigned int i;for (i = 0; i < vb->num_planes; ++i) {call_memop(q, unmap_dmabuf, vb->planes[i].mem_priv);vb->planes[i].dbuf_mapped = 0;}}
switch (vb->state) { case VB2_BUF_STATE_DONE: