graesslin created this revision. Restricted Application added a project: KWin. Restricted Application added subscribers: kwin, plasma-devel.
REVISION SUMMARY The base idea behind this change is to keep the system responsive no matter what other processes do. All input and rendering needs to go through the windowing system, so keeping it responsive is important. Currently KWin competes with all other processes for resources and this can render the system unusable. Consider some processes running amok. In this case the user might not be able to easily close the applications as KWin does not get the cpu time to perform the input tasks requested by the user. Or in the case of playing a demanding game it is important that KWin gets scheduled to forward the pointer input events. The user doesn't want that the game (or another process) wins against the windowing sytem. The disadvantage is that KWin always wins against other processes with real time scheduling. This could result in KWin running amok stalling the system. On the other hand this is no change to the current situation as if KWin runs amok the sytem is unusable. The change uses libcap to set CAP_SYS_NICE on kwin_wayland executable. KWin_wayland on start sets the scheduling policy to SCHED_RR with the lowest possible priority. Thus any other SCHED_RR process will win against KWin. So real time processes are not affected by this change! After adjusting the scheduling (which requires CAP_SYS_NICE) KWin drops this capability again. TEST PLAN Verified that KWin adjusts the scheduler, that it is not passed to child processes, that the capability gets dropped and not passed to child processes. REPOSITORY R108 KWin BRANCH wayland-realtime REVISION DETAIL https://phabricator.kde.org/D7757 AFFECTED FILES CMakeLists.txt cmake/modules/FindLibcap.cmake config-kwin.h.cmake main_wayland.cpp To: graesslin, #kwin, #plasma Cc: plasma-devel, kwin, bwowk, ZrenBot, progwolff, lesliezhai, ali-mohamed, hardening, jensreuterberg, abetts, sebas, apol, mart
