Uclamp exposes 3 sysctl knobs:
* sched_util_clamp_min
* sched_util_clamp_max
* sched_util_clamp_min_rt_default
Document them in sysctl/kernel.rst.
Signed-off-by: Qais Yousef <qais.you...@arm.com>
CC: Jonathan Corbet <cor...@lwn.net>
CC: Juri Lelli <juri.le...@redhat.com>
CC: Vincent Guittot <vincent.guit...@linaro.org>
CC: Dietmar Eggemann <dietmar.eggem...@arm.com>
CC: Steven Rostedt <rost...@goodmis.org>
CC: Ben Segall <bseg...@google.com>
CC: Mel Gorman <mgor...@suse.de>
CC: Luis Chamberlain <mcg...@kernel.org>
CC: Kees Cook <keesc...@chromium.org>
CC: Iurii Zaikin <yzai...@google.com>
CC: Quentin Perret <qper...@google.com>
CC: Valentin Schneider <valentin.schnei...@arm.com>
CC: Patrick Bellasi <patrick.bell...@matbug.net>
CC: Pavan Kondeti <pkond...@codeaurora.org>
CC: linux-...@vger.kernel.org
CC: linux-kernel@vger.kernel.org
CC: linux-fsde...@vger.kernel.org
---
Documentation/admin-guide/sysctl/kernel.rst | 48 +++++++++++++++++++++
1 file changed, 48 insertions(+)
diff --git a/Documentation/admin-guide/sysctl/kernel.rst
b/Documentation/admin-guide/sysctl/kernel.rst
index 0d427fd10941..e7255f71493c 100644
--- a/Documentation/admin-guide/sysctl/kernel.rst
+++ b/Documentation/admin-guide/sysctl/kernel.rst
@@ -940,6 +940,54 @@ Enables/disables scheduler statistics. Enabling this
feature
incurs a small amount of overhead in the scheduler but is
useful for debugging and performance tuning.
+sched_util_clamp_min:
+=====================
+
+Max allowed *minimum* utilization.
+
+Default value is SCHED_CAPACITY_SCALE (1024), which is the maximum possible
+value.
+
+It means that any requested uclamp.min value cannot be greater than
+sched_util_clamp_min, ie: it is restricted to the range
+[0:sched_util_clamp_min].
+
+sched_util_clamp_max:
+=====================
+
+Max allowed *maximum* utilization.
+
+Default value is SCHED_CAPACITY_SCALE (1024), which is the maximum possible
+value.
+
+It means that any requested uclamp.max value cannot be greater than
+sched_util_clamp_max, ie: it is restricted to the range
+[0:sched_util_clamp_max].
+
+sched_util_clamp_min_rt_default:
+================================
+
+By default Linux is tuned for performance. Which means that RT tasks always run
+at the highest frequency and most capable (highest capacity) CPU (in
+heterogeneous systems).
+
+Uclamp achieves this by setting the requested uclamp.min of all RT tasks to
+SCHED_CAPACITY_SCALE (1024) by default. Which effectively boosts the tasks to
+run at the highest frequency and bias them to run on the biggest CPU.
+
+This knob allows admins to change the default behavior when uclamp is being
+used. In battery powered devices particularly, running at the maximum
+capacity and frequency will increase energy consumption and shorten the battery
+life.
+
+This knob is only effective for RT tasks which the user hasn't modified their
+requested uclamp.min value via sched_setattr() syscall.
+
+This knob will not escape the constraint imposed by sched_util_clamp_min
+defined above.
+
+Any modification is applied lazily on the next opportunity the scheduler needs
+to calculate the effective value of uclamp.min of the task.
seccomp
=======
--
2.17.1
