From mboxrd@z Thu Jan 1 00:00:00 1970 From: Srinivas Pandruvada Subject: [PATCH v2 3/3] Documentation: intel_pstate: Add energy performance hint Date: Tue, 6 Dec 2016 13:32:17 -0800 Message-ID: <1481059937-193048-4-git-send-email-srinivas.pandruvada@linux.intel.com> References: <1481059937-193048-1-git-send-email-srinivas.pandruvada@linux.intel.com> Return-path: Received: from mga04.intel.com ([192.55.52.120]:30593 "EHLO mga04.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752037AbcLFVcq (ORCPT ); Tue, 6 Dec 2016 16:32:46 -0500 In-Reply-To: <1481059937-193048-1-git-send-email-srinivas.pandruvada@linux.intel.com> Sender: linux-pm-owner@vger.kernel.org List-Id: linux-pm@vger.kernel.org To: lenb@kernel.org, rjw@rjwysocki.net Cc: linux-pm@vger.kernel.org, Srinivas Pandruvada Updated documentation for the support of energy performance hint. Signed-off-by: Srinivas Pandruvada --- Documentation/cpu-freq/intel-pstate.txt | 24 ++++++++++++++++++++++++ 1 file changed, 24 insertions(+) diff --git a/Documentation/cpu-freq/intel-pstate.txt b/Documentation/cpu-freq/intel-pstate.txt index 198b2ef..012170e 100644 --- a/Documentation/cpu-freq/intel-pstate.txt +++ b/Documentation/cpu-freq/intel-pstate.txt @@ -139,6 +139,30 @@ architecture of the processor permits: - User can read write system wide turbo status /sys/devices/system/cpu/no_turbo +Support of energy performance hint +It is possible to provide hints to the HWP algorithms in the processor +to be more performance centric to more energy centric. When driver is +using HWP, two additional cpufreq sysfs attributes are presented for +each logical CPU. +These attributes are: + - energy_performance_available_preferences + - energy_performance_preference + +To get list of supported hints: +$ cat energy_performance_available_preferences + default performance balance_performance balance_power power + +The current preference can be read or changed via cpufreq sysfs +attribute "energy_performance_preference". Reading from this attribute +will display current effective setting. User can write any of the valid +preference string to this attribute. User can always restore to power-on +default by writing "default". + +Since threads can migrate to different CPUs, this is possible that the +new CPU may have different energy performance preference than the previous +one. To avoid such issues, either threads can be pinned to specific CPUs +or set the same energy performance preference value to all CPUs. + Tuning Intel P-State driver When the performance can be tuned using PID (Proportional Integral -- 2.7.4