Launchpad has imported 2 comments from the remote bug at https://bugs.freedesktop.org/show_bug.cgi?id=86366.
If you reply to an imported comment from within Launchpad, your comment will be sent to the remote bug automatically. Read more about Launchpad's inter-bugtracker facilities at https://help.launchpad.net/InterBugTracking. ------------------------------------------------------------------------ On 2014-11-17T03:43:35+00:00 Daniel van Vugt wrote: In the Mir server code (DRI output) we call: 1. eglSwapBuffers() 2. get the new front buffer 3. schedule a page flip: drmModePageFlip() This works well, however if I force it to wait for the page flip immediately: 4. select() on the DRM fd and then drmHandleEvent() then step 4 (under some rare but predictable rendering loads) takes 32ms to complete. I've now confirmed it is just the page flip event that takes almost two frames to arrive. And there are two workarounds that seem to successfully kick the driver into action: 3.5. glFinish() or 0. env INTEL_DEBUG=sync Using either of these workarounds, rendering completes in about 1ms and select then returns the next page flip event (~16ms interval). So it seems the intel batching logic is deferring rendering way too long, or the page flip event delivery is being deferred. However the two workarounds suggest the former. Using: Mesa 10.3.2-0ubuntu1 (Ubuntu 15.04 vivid) Intel® HD Graphics 4600 (Intel(R) Core(TM) i7-4770 CPU @ 3.40GHz) Reply at: https://bugs.launchpad.net/mir/+bug/1377872/comments/5 ------------------------------------------------------------------------ On 2014-11-17T04:04:10+00:00 Daniel van Vugt wrote: I wonder if this is just a race? If the page flip actually completes faster than select() takes to start up then that would explain it. Reply at: https://bugs.launchpad.net/mir/+bug/1377872/comments/7 ** Changed in: mesa Status: Unknown => Confirmed ** Changed in: mesa Importance: Unknown => Medium -- You received this bug notification because you are a member of Ubuntu-X, which is subscribed to mesa in Ubuntu. https://bugs.launchpad.net/bugs/1377872 Title: Double-buffered compositing performance is very poor (30 FPS) To manage notifications about this bug go to: https://bugs.launchpad.net/mesa/+bug/1377872/+subscriptions _______________________________________________ Mailing list: https://launchpad.net/~ubuntu-x-swat Post to : ubuntu-x-swat@lists.launchpad.net Unsubscribe : https://launchpad.net/~ubuntu-x-swat More help : https://help.launchpad.net/ListHelp
