Hello! On 22/05/25 17:06, Shashank Balaji wrote: > Setting the cpu affinity mask of a SCHED_DEADLINE process using the cgroup v1 > cpuset controller is already detailed. Add similar information for cgroup v2's > cpuset controller. Thanks a lot for working on this. Really appreaciated. > Signed-off-by: Shashank Balaji <shashank.mahadasyam@xxxxxxxx> > --- > Documentation/scheduler/sched-deadline.rst | 29 +++++++++++++++++++++++------ > 1 file changed, 23 insertions(+), 6 deletions(-) > > diff --git a/Documentation/scheduler/sched-deadline.rst b/Documentation/scheduler/sched-deadline.rst > index a727827b8dd52710f880c2b92d3a8224c259873c..e3d7968ff6c3c43f87e249dbcb309619dbd616bf 100644 > --- a/Documentation/scheduler/sched-deadline.rst > +++ b/Documentation/scheduler/sched-deadline.rst > @@ -20,7 +20,8 @@ Deadline Task Scheduling > 4.3 Default behavior > 4.4 Behavior of sched_yield() > 5. Tasks CPU affinity > - 5.1 SCHED_DEADLINE and cpusets HOWTO > + 5.1 Using cgroup v1 cpuset controller > + 5.2 Using cgroup v2 cpuset controller > 6. Future plans > A. Test suite > B. Minimal main() > @@ -671,12 +672,15 @@ Deadline Task Scheduling > 5. Tasks CPU affinity > ===================== > > - -deadline tasks cannot have an affinity mask smaller that the entire > - root_domain they are created on. However, affinities can be specified > - through the cpuset facility (Documentation/admin-guide/cgroup-v1/cpusets.rst). > + Deadline tasks cannot have a cpu affinity mask smaller than the root domain they > + are created on. So, using ``sched_setaffinity(2)`` won't work. Instead, the > + the deadline task should be created in a restricted root domain. This can be > + done using the cpuset controller of either cgroup v1 (deprecated) or cgroup v2. > + See :ref:`Documentation/admin-guide/cgroup-v1/cpusets.rst <cpusets>` and > + :ref:`Documentation/admin-guide/cgroup-v2.rst <cgroup-v2>` for more information. > > -5.1 SCHED_DEADLINE and cpusets HOWTO > ------------------------------------- > +5.1 Using cgroup v1 cpuset controller > +------------------------------------- > > An example of a simple configuration (pin a -deadline task to CPU0) > follows (rt-app is used to create a -deadline task):: > @@ -695,6 +699,19 @@ Deadline Task Scheduling > rt-app -t 100000:10000:d:0 -D5 # it is now actually superfluous to specify > # task affinity > > +5.2 Using cgroup v2 cpuset controller > +------------------------------------- > + > + Assuming the cgroup v2 root is mounted at ``/sys/fs/cgroup``. > + > + cd /sys/fs/cgroup > + echo '+cpuset' > cgroup.subtree_control > + mkdir deadline_group > + echo 0 > deadline_group/cpuset.cpus > + echo 'root' > deadline_group/cpuset.cpus.partition > + echo $$ > deadline_group/cgroup.procs > + rt-app -t 100000:10000:d:0 -D5 Sadly, the example with cgroup v1 was made at a time when rt-app still supported command line parameters like the above. I believe nowadays that is not the case anymore and one needs to create a json file describing the task to run it with rt-app. I would say we should update both examples to use something a little more generic, e.g., # chrt --deadline --sched-runtime 10000000 --sched-period 100000000 0 yes >/dev/null & What do you think? Best, Juri
