module-rt: enable setting UCLAMP_MIN and UCLAMP_MAX values

Modern heterogenous multiprocessor systems rely increasingly on
scheduler hinting for efficiency gains and system optimisation.
This is especially true on embedded systems, where background
tasks such as audio daemons should be consigned to the most
power-efficient core in the system. Left to its own devices, the
Linux Completely Fair Scheduler tends to migrate Pipewire to
more performant cores, even when this is unnecessary.

Luckily, CFS can be told by a task to clamp its utilisation values.
Coupled with energy-aware scheduling, this allows the scheduler to
make better informed decisions about where tasks should be placed,
and what pstate to set for the CPU it is running on.

Enable the user to configure UCLAMP_MIN and UCLAMP_MAX values via
arguments to libpipewire-module-rt.

Signed-off-by: James Calligeros <jcalligeros99@gmail.com>

src/daemon/pipewire-pulse.conf.in

@@ -31,6 +31,8 @@ context.modules = [
             rt.prio      = 65
             #rt.time.soft = -1
             #rt.time.hard = -1
+            #uclamp.min = 0
+            #uclamp.max = 1024
         }
         flags = [ ifexists nofail ]
     }

src/daemon/pipewire.conf.in

@@ -90,13 +90,16 @@ context.modules = [
 
     # Uses realtime scheduling to boost the audio thread priorities. This uses
     # RTKit if the user doesn't have permission to use regular realtime
-    # scheduling.
+    # scheduling. You can also clamp utilisation values to improve scheduling
+    # on embedded and heterogeneous systems, e.g. Arm big.LITTLE devices.
     { name = libpipewire-module-rt
         args = {
             nice.level    = -11
             #rt.prio      = 88
             #rt.time.soft = -1
             #rt.time.hard = -1
+            #uclamp.min = 0
+            #uclamp.max = 1024
         }
         flags = [ ifexists nofail ]
     }