Hi Gibro,<br><br>Thanks for the kind reply. Even I remove the memcpy in v4l2src, the overhead is still there. I guess the overhead is just shifted to another stage that consumes the data. I found the problem was with the coherent buffer used in the driver, since the v4l2 driver I am investigating uses the buffer queue defined in videobuf-dma-contig.c. After I replace the coherent buffers with streaming buffers, the problem goes away. <br> <br>One correction to my previous email. The memory should "contiguous" instead of "contingent"<br><br>Best regards,<br>Yiliang<br><br><div class="gmail_quote">On Fri, Jan 22, 2010 at 11:48 PM, Gibro Vacco <span dir="ltr"><<a href="mailto:gibrovacco@gmail.com">gibrovacco@gmail.com</a>></span> wrote:<br> <blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"><div class="im">Hi,<br> <br> would it ber possible to mmap the memory are from the driver so that<br> v4l2src passes that very buffer to the remaining of the pipeline?<br> <br> The only problem would be that, in case of a circular buffer in the<br> driver, each memory area will remain locked until the pipeline has<br> ended processing it.<br> <br> </div><div class="im">On Thu, Jan 21, 2010 at 12:57 AM, yiliang <<a href="mailto:yiliangb@gmail.com">yiliangb@gmail.com</a>> wrote:<br> ><br> > Hi,<br> ><br> > I am optimizing a V4L2 driver for video capture device. In the v4l2 driver,<br> > the DMA is performed based on frames using contingent memory buffers. After<br> > a frame is captured, the frame data is copied to a application buffer in<br> > v4l2src.<br> ><br> > gst_v4l2src_grab_frame()<br> > -> *buf = gst_buffer_copy (pool_buffer);<br> ><br> > However, the time spent on copying the buffer is very costly, about 0.01<br> > seconds, which is very large considering frame time is only 0.033 seconds.<br> ><br> > I do not know whether this is the right forum. Any suggestions will be<br> > appreciated.<br> ><br> > Thanks,<br> > Yiliang<br> ><br> > --<br> > View this message in context: <a href="http://n4.nabble.com/Help-needed-to-reduce-unusually-high-CPU-utilization-in-v4l2src-caused-by-memory-copy-tp1019508p1019508.html" target="_blank">http://n4.nabble.com/Help-needed-to-reduce-unusually-high-CPU-utilization-in-v4l2src-caused-by-memory-copy-tp1019508p1019508.html</a><br> > Sent from the GStreamer-devel mailing list archive at Nabble.com.<br> ><br> > ------------------------------------------------------------------------------<br> > Throughout its 18-year history, RSA Conference consistently attracts the<br> > world's best and brightest in the field, creating opportunities for Conference<br> > attendees to learn about information security's most important issues through<br> > interactions with peers, luminaries and emerging and established companies.<br> > <a href="http://p.sf.net/sfu/rsaconf-dev2dev" target="_blank">http://p.sf.net/sfu/rsaconf-dev2dev</a><br> > _______________________________________________<br> > gstreamer-devel mailing list<br> </div>> <a href="mailto:gstreamer-devel@lists.sourceforge.net">gstreamer-devel@lists.sourceforge.net</a><br> <div class="im">> <a href="https://lists.sourceforge.net/lists/listinfo/gstreamer-devel" target="_blank">https://lists.sourceforge.net/lists/listinfo/gstreamer-devel</a><br> ><br> <br> ------------------------------------------------------------------------------<br> Throughout its 18-year history, RSA Conference consistently attracts the<br> world's best and brightest in the field, creating opportunities for Conference<br> attendees to learn about information security's most important issues through<br> interactions with peers, luminaries and emerging and established companies.<br> <a href="http://p.sf.net/sfu/rsaconf-dev2dev" target="_blank">http://p.sf.net/sfu/rsaconf-dev2dev</a><br> _______________________________________________<br> gstreamer-devel mailing list<br> </div><a href="mailto:gstreamer-devel@lists.sourceforge.net">gstreamer-devel@lists.sourceforge.net</a><br> <div><div></div><div class="h5"><a href="https://lists.sourceforge.net/lists/listinfo/gstreamer-devel" target="_blank">https://lists.sourceforge.net/lists/listinfo/gstreamer-devel</a><br> </div></div></blockquote></div><br>