From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Pallipadi, Venkatesh" Subject: [PATCH] Add decaying history logic to cpuidle menu idle predictor Date: Tue, 30 Dec 2008 14:46:02 -0800 Message-ID: <20081230224602.GA6898@linux-os.sc.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from mga03.intel.com ([143.182.124.21]:4996 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753259AbYL3WqD (ORCPT ); Tue, 30 Dec 2008 17:46:03 -0500 Content-Disposition: inline Sender: linux-acpi-owner@vger.kernel.org List-Id: linux-acpi@vger.kernel.org To: Len Brown Cc: linux-acpi@vger.kernel.org, yakui.zhao@intel.com Add decaying history of predicted idle time, instead of using the last early wakeup. This logic helps menu governor do better job of predicting idle time. With this change, we also measured noticable (~8%) power savings on a DP server system with CPUs supporting deep C states, when system was lightly loaded. There was no change to power or perf on other load conditions. Signed-off-by: Venkatesh Pallipadi --- drivers/cpuidle/governors/menu.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) Index: linux-2.6/drivers/cpuidle/governors/menu.c =================================================================== --- linux-2.6.orig/drivers/cpuidle/governors/menu.c 2008-11-10 15:27:13.000000000 -0800 +++ linux-2.6/drivers/cpuidle/governors/menu.c 2008-12-30 14:39:15.000000000 -0800 @@ -15,12 +15,14 @@ #include #define BREAK_FUZZ 4 /* 4 us */ +#define PRED_HISTORY_PCT 50 struct menu_device { int last_state_idx; unsigned int expected_us; unsigned int predicted_us; + unsigned int current_predicted_us; unsigned int last_measured_us; unsigned int elapsed_us; }; @@ -47,6 +49,12 @@ static int menu_select(struct cpuidle_de data->expected_us = (u32) ktime_to_ns(tick_nohz_get_sleep_length()) / 1000; + /* Recalculate predicted_us based on prediction_history_pct */ + data->predicted_us *= PRED_HISTORY_PCT; + data->predicted_us += (100 - PRED_HISTORY_PCT) * + data->current_predicted_us; + data->predicted_us /= 100; + /* find the deepest idle state that satisfies our constraints */ for (i = CPUIDLE_DRIVER_STATE_START + 1; i < dev->state_count; i++) { struct cpuidle_state *s = &dev->states[i]; @@ -97,7 +105,7 @@ static void menu_reflect(struct cpuidle_ measured_us = -1; /* Predict time until next break event */ - data->predicted_us = max(measured_us, data->last_measured_us); + data->current_predicted_us = max(measured_us, data->last_measured_us); if (last_idle_us + BREAK_FUZZ < data->expected_us - target->exit_latency) {