As I've tracked the issue into the intel driver code and the workarounds for test case A don't help B, we might have to split this bug in two.
** Description changed: Double-buffered compositing performance is poor. Fortunately we don't use double-buffering in our default compositor (mostly), and Ubuntu touch does not use the default compositor either. However, if you make the compositor double-buffered, then it quickly drops down to 30 FPS while not consuming any significant CPU or render time. Test case A: Convert your compositor to double buffering by the code change suggested in bug 1350725. - Test case B: + Test case B (different bug?): Switch all clients to double-buffering using this branch: lp:~vanvugt/mir/double and then start a nested server. Now start a bunch of clients, and you will find they slow down to 30 FPS after only starting a few. This does not happen with the default triple buffered compositor. I've been ignoring this issue for a little while [1] thinking I had simply run out of power, although suspected that can't be right as this is a powerful quad-core i7 and it's slowing down with only 10 clients. [1] https://bugs.launchpad.net/mir/+bug/1350725/comments/1 Now today test case B has revealed (via MIR_CLIENT_PERF_REPORT) that the slowdown happens without using any significant render time (less than 2 ms) and without using any significant CPU (less than 20% of one out of four cores). So the conclusion is our default compositor is probably holding buffers for a little too long somewhere. Because that's the only sensible reason I can think of for my system to bog down to 30 FPS without stressing the CPU or GPU. We've got poor parallelism in our code somewhere. And once that's solved, we'll be able to make further improvements such as resolving bug 1350725. ** Changed in: mir Assignee: Cemil Azizoglu (cemil-azizoglu) => Daniel van Vugt (vanvugt) ** Bug watch added: freedesktop.org Bugzilla #86366 https://bugs.freedesktop.org/show_bug.cgi?id=86366 ** Also affects: mesa via https://bugs.freedesktop.org/show_bug.cgi?id=86366 Importance: Unknown Status: Unknown ** Also affects: mesa (Ubuntu) Importance: Undecided Status: New -- 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