From: David Vernet To: "Rafael J. Wysocki" Cc: "Mario Limonciello" , "Gautham R. Shenoy" , linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org, "André Almeida" , "Changwoo Min" Subject: [RFC PATCH 4/4] Documentation: amd-pstate: Document the epp_boost parameter Date: Tue, 28 Jul 2026 02:31:50 -0500 [thread overview] Message-ID: <20260728073150.54964-5-void@manifault.com> (raw) In-Reply-To: <20260728073150.54964-1-void@manifault.com> Document the per-core EPP boost mechanism and its epp_boost module parameter added by the previous patch. Signed-off-by: David Vernet --- Documentation/admin-guide/pm/amd-pstate.rst | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) diff --git a/Documentation/admin-guide/pm/amd-pstate.rst b/Documentation/admin-guide/pm/amd-pstate.rst index a95e2ebce005..004b79ff925c 100644 --- a/Documentation/admin-guide/pm/amd-pstate.rst +++ b/Documentation/admin-guide/pm/amd-pstate.rst @@ -372,6 +372,22 @@ based on the power source and will not react to user desired power state. Attempting to manually write to the ``energy_performance_preference`` sysfs file will fail when ``dynamic_epp`` is enabled. +Energy performance preference boosting +====================================== +On MSR-based systems running in the ``active mode``, the driver can optionally +bias the energy performance preference of a recently-busy CPU toward +performance while leaving all other CPUs at the policy value. C0 residency is +sampled at most every 10 ms; while a CPU has been at least 50% busy within the +last 300 ms, the EPP field of its CPPC request is set to ``performance`` (0). +The policy value is restored once 300 ms pass without a busy sample. + +This behavior is disabled by default. It can be enabled with the module +parameter ``amd_pstate.epp_boost=1`` on the kernel command line, or at runtime +by writing ``1`` to ``/sys/module/amd_pstate/parameters/epp_boost``. The +mechanism only runs while the parameter is enabled and has no overhead when +disabled. It has no effect in the ``passive`` and ``guided`` modes or on +shared-memory (non-MSR) systems. + ``amd-pstate`` vs ``acpi-cpufreq`` ====================================== -- 2.53.0