[systemd-devel] [lennart at kemper.freedesktop.org: [systemd-commits] src/pam-module.c]

[Lennart Poettering]

On Fri, 11.02.11 10:30, fykcee1 at gmail.com (fykcee1 at gmail.com) 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.