[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-Id: <1336749357-9133-3-git-send-email-youquan.song@intel.com>
Date: Fri, 11 May 2012 11:15:56 -0400
From: Youquan Song <youquan.song@...el.com>
To: linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-pm@...ts.linux-foundation.org, len.brown@...el.com,
akpm@...ux-foundation.org
Cc: arjan@...ux.intel.com, len.brown@...ux.intel.com,
suresh.b.siddha@...el.com,
Youquan Song <youquan.song@...ux.intel.com>,
Youquan Song <youquan.song@...el.com>
Subject: [PATCH 2/3] x86,idle: Quickly notice prediction failure in general case
The patch extends the patch to enhance the prediction for repeat mode by add a
timer when menu governor choose a shallow C-state.
The timer is set to time out in 50 milli-seconds by default. It is special twist
that there are no power saving gains even sleep longer than it.
When C-state is waken up prior to the adding timer, the timer will be cancelled
initiatively. When the timer is triggered and menu governor will quickly notice
prediction failure and re-evaluates deeper C-states possibility.
Signed-off-by: Youquan Song <youquan.song@...el.com>
---
drivers/cpuidle/governors/menu.c | 48 ++++++++++++++++++++++++++------------
1 files changed, 33 insertions(+), 15 deletions(-)
diff --git a/drivers/cpuidle/governors/menu.c b/drivers/cpuidle/governors/menu.c
index 8c23fbd..9f92dd4 100644
--- a/drivers/cpuidle/governors/menu.c
+++ b/drivers/cpuidle/governors/menu.c
@@ -113,6 +113,13 @@ static DEFINE_PER_CPU(int, hrtimer_started);
* represented in the system load average.
*
*/
+
+/*
+ * Default set to 50 milliseconds based on special twist mentioned above that
+ * there are no power gains sleep longer than it.
+ */
+static unsigned int perfect_cstate_ms __read_mostly = 50;
+module_param(perfect_cstate_ms, uint, 0000);
struct menu_device {
int last_state_idx;
@@ -343,26 +350,37 @@ static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev)
data->exit_us = s->exit_latency;
}
}
-
+
+ /* not deepest C-state chosen */
if (data->last_state_idx < drv->state_count - 1) {
+ unsigned int repeat_us = 0;
+ unsigned int perfect_us = 0;
+
+ /*
+ * Set enough timer to recognize the repeat mode broken.
+ * If the timer is time out, the repeat mode prediction
+ * fails,then re-evaluate deeper C-states possibility.
+ * If the timer is not triggered, the timer will be
+ * cancelled when CPU waken up.
+ */
+ repeat_us =
+ (repeat ? (2 * data->predicted_us + MAX_DEVIATION) : 0);
+ perfect_us = perfect_cstate_ms * 1000;
/* Repeat mode detected */
- if (repeat) {
- unsigned int repeat_us = 0;
- /*
- * Set enough timer to recognize the repeat mode broken.
- * If the timer is time out, the repeat mode prediction
- * fails,then re-evaluate deeper C-states possibility.
- * If the timer is not triggered, the timer will be
- * cancelled when CPU waken up.
- */
- repeat_us = 2 * data->predicted_us + MAX_DEVIATION;
- hrtimer_start(hrtmr, ns_to_ktime(1000 * repeat_us),
- HRTIMER_MODE_REL_PINNED);
+ if (repeat && (repeat_us < perfect_us)) {
+ hrtimer_start(hrtmr, ns_to_ktime(1000 * repeat_us),
+ HRTIMER_MODE_REL_PINNED);
+ /* menu hrtimer is started */
+ per_cpu(hrtimer_started, cpu) = 1;
+ } else if (perfect_us < data->expected_us) {
+ /* expected time is larger than adding timer time */
+ hrtimer_start(hrtmr, ns_to_ktime(1000 * perfect_us),
+ HRTIMER_MODE_REL_PINNED);
/* menu hrtimer is started */
per_cpu(hrtimer_started, cpu) = 1;
- }
- }
+ }
+ }
return data->last_state_idx;
}
--
1.6.4.2
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists