<div class="gmail_quote">On Mon, Mar 28, 2011 at 9:35 AM, Chia-I Wu <<a href="mailto:olvaffe@gmail.com">olvaffe@gmail.com</a>> wrote: <blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;"> Hi list, I have a simple scenario that there are clients rendering to buffer objects using the CPU, and the display server compositing the buffers using OpenGL and doing page flips to present the final contents. It is like doing the following steps repeatedly 1) process A (the server) allocates a bo bo = radeon_bo_open(info->bufmgr, 0, size, align, RADEON_GEM_DOMAIN_GTT, 0); 2) process B (the client) maps the bo for CPU rendering and unmaps radeon_bo_map(bo, 1); /* ...render with CPU... */ radeon_bo_unmap(bo); 3) process A renders to the back buffer using the bo as the texture /* renders with OpenGL followed by a glFinish() */ 4) process A flips its front and back buffers drmModePageFlip(fd, crtc_id, fb_id_of_the_bo, 0x0, NULL); drmWaitVBlank(fd, &vbl); /* HACK! wait until the next vblank */ With this setup, I am seeing glitches frequently. My hardware is a CEDAR. The kernel is 2.6.38-rc7 and both mesa and drm are from master. I originally ran them on a i965-based machine using libdrm_i915, and it is fine there. I think there are sync issues in how I use libdrm_radeon, but I could not identify them. Here are my findings/questions In 1), The bo is initially in the GTT domain because CPU rendering is expected. Using VRAM domain reduces the glitches greatly, but there are still glitches and the framerate is much lower. In 3), glFinish() is called after rendering to make sure the frame is complete before page flipping. Does glFlush() suffice here? I think that would require page flipping to be pipelined, but I am not sure if that is the case with radeon. </blockquote></div> glFinish uses fences, which are not implemented in r600g (and there is no wait-for-a-fence ioctl), so glFinish=glFlush. Could that be the cause of your problems? The other radeon drivers use bo_wait for glFinish (including r300g). Marek