Hi Lennart, Thanks for the explanation. IMHO, To re-enable user session 'cpu' sorting: a) Desktop distributions disable GROUP_RT in the kernel, then no rt_bandwidth, all RT-apps can be fully administrated under rtkit.
Or b) cpu cgroup controller should default make sub-cgroups share rt_bandwidth with their parent. Internally, kernel uses two separate hierarchies for NORMAL and RT processes, current logic should be changed as: a new cgroup with a cpu controller will add a new level in 'NORMAL hierarchy', but not touch 'RThierarchy' unless set sched_rt_runtime_us. 2011/2/14 Lennart Poettering <[email protected]> > On Fri, 11.02.11 10:30, [email protected] ([email protected]) wrote: > > > Hi Lennart, Andrey, > > > > Some questions about the discuss: > > 1. Does systemd re-enable sorting user sessions into their own cgroups > in > > the 'cpu' hierarchy? > > No, we cannot reenable that before the cpu cgroup controller gets fixed. > > On current kernels doing this kind of sorting means practically that all > processes we sort into a 'cpu' cgroup lose their capability to use RT > scheduling. > > I am not aware of any typical daemon we ship that would use RT > scheduling hence we are keeping the default 'cpu' cgroup sorting for > system daemons enabled. However user applications are more likely to use > RT (for example PA does) and hence we have disabled this for sessions > for now. > > > 2. AIUI, rtkit is a daemon used for doing RT-related privilege > operations. > > It doesn't spawn RT-threads. Am I right? > > It does use RT privs for the implementatin of the canary watchdog. > > > 3. Does rtkit have related systemd service file? Does it run at its own > > cgroup with controller=cpu? If yes, how does the cgroup receive > > rt-bandwidth(period time, run time)? > > rtkit comes with a systemd unit file. In rtkit git this unit file > ensures that rtkit is explicitly moved into the root "cpu" cgroup so > that it can make use of RT scheduling -- if you so will rtkit is the one > exception to what i mentioned above regarding no system daemons using > RT. > > Lennart > > -- > Lennart Poettering - Red Hat, Inc. > -- Regards, - cee1
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