On Tue, Mar 29, 2011 at 12:59 AM, Marek OlÅÃk <maraeo@xxxxxxxxx> wrote: > On Mon, Mar 28, 2011 at 9:35 AM, Chia-I Wu <olvaffe@xxxxxxxxx> wrote: >> >> 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. ÂIt >> is like doing the following steps repeatedly >> >> 1) process A (the server) allocates a bo >> >> Â 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 >> >> Â radeon_bo_map(bo, 1); >> Â /* ...render with CPU... */ >> Â radeon_bo_unmap(bo); >> >> 3) process A renders to the back buffer using the bo as the texture >> >> Â /* renders with OpenGL followed by a glFinish() */ >> >> 4) process A flips its front and back buffers >> >> Â drmModePageFlip(fd, crtc_id, fb_id_of_the_bo, 0x0, NULL); >> Â drmWaitVBlank(fd, &vbl); /* HACK! wait until the next vblank */ >> >> With this setup, I am seeing glitches frequently. ÂMy hardware is a >> CEDAR. ÂThe kernel is 2.6.38-rc7 and both mesa and drm are from >> master. ÂI 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. ÂHere are my findings/questions >> >> In 1), The bo is initially in the GTT domain because CPU rendering is >> expected. ÂUsing 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. ÂDoes glFlush() suffice here? ÂI think >> that would require page flipping to be pipelined, but I am not sure if >> that is the case with radeon. > > 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). It turned out to be 4) that causes the glitches. It is resolved by using DRM_MODE_PAGE_FLIP_EVENT as mentioned in the last mail. But drmModePageFlip still needs to be fixed to block rendering to the previous scanout buffer until the flip takes place. > Marek > _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/dri-devel
