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Message-ID: <20080306092730.4412d085@mjolnir.drzeus.cx>
Date: Thu, 6 Mar 2008 09:27:30 +0100
From: Pierre Ossman <drzeus-list@...eus.cx>
To: unlisted-recipients:; (no To-header on input)
Cc: "Pallipadi, Venkatesh" <venkatesh.pallipadi@...el.com>,
"Dave Jones" <davej@...emonkey.org.uk>,
"Andi Kleen" <andi@...stfloor.org>,
"Alan Stern" <stern@...land.harvard.edu>,
"LKML" <linux-kernel@...r.kernel.org>,
"Adam Belay" <abelay@...ell.com>,
"Lee Revell" <rlrevell@...-job.com>,
linux-pm@...ts.linux-foundation.org, "Pavel Machek" <pavel@....cz>
Subject: Re: [linux-pm] [PATCH] cpuidle: avoid singing capacitors
On Wed, 5 Mar 2008 09:40:23 +0100
Pierre Ossman <drzeus-list@...eus.cx> wrote:
>
> So I need to build some global algorithm instead of one per core. Ideas are welcome.
>
I'm currently trying this variant. No noise yet, but the time spent in C3 seems to take a massive hit. I'll see if I can get around to some kind of power measurement (ideas for doing that in a sane way are still welcome btw).
diff --git a/drivers/cpuidle/governors/menu.c b/drivers/cpuidle/governors/menu.c
index 78d77c5..960aa39 100644
--- a/drivers/cpuidle/governors/menu.c
+++ b/drivers/cpuidle/governors/menu.c
@@ -16,6 +16,11 @@
#define BREAK_FUZZ 4 /* 4 us */
+static unsigned int min_deep_sleep = 0;
+static unsigned int failed_deep = 0;
+
+static unsigned long global_last_deep;
+
struct menu_device {
int last_state_idx;
@@ -23,6 +28,8 @@ struct menu_device {
unsigned int predicted_us;
unsigned int last_measured_us;
unsigned int elapsed_us;
+
+ unsigned long last_deep;
};
static DEFINE_PER_CPU(struct menu_device, menu_devices);
@@ -50,9 +57,51 @@ static int menu_select(struct cpuidle_device *dev)
break;
if (s->exit_latency > pm_qos_requirement(PM_QOS_CPU_DMA_LATENCY))
break;
+
+ /*
+ * In order to avoid the problem of "singing capacitors",
+ * don't enter a deep sleep for short durations (2 ms seems
+ * to do the trick). This will, hopefully, keep the problem
+ * inaudible.
+ */
+ if (min_deep_sleep && (s->flags & CPUIDLE_FLAG_DEEP)) {
+ if (time_before_eq(jiffies, data->last_deep +
+ HZ * min_deep_sleep / USEC_PER_SEC))
+ break;
+
+ rmb();
+
+ if (time_before_eq(jiffies, global_last_deep +
+ HZ * min_deep_sleep / USEC_PER_SEC))
+ break;
+
+#if 0
+ if (min_deep_sleep > data->expected_us)
+ break;
+ if (min_deep_sleep > cpuidle_get_last_residency(dev))
+ break;
+#endif
+#if 0
+ if (min_deep_sleep > data->predicted_us)
+ break;
+ if (min_deep_sleep > data->last_measured_us)
+ break;
+#endif
+ }
}
data->last_state_idx = i - 1;
+
+ if (dev->states[i - 1].flags & CPUIDLE_FLAG_DEEP) {
+#if 0
+ printk("Sleep interval: %ld jiffies\n",
+ jiffies - data->last_deep);
+#endif
+ data->last_deep = jiffies;
+ global_last_deep = jiffies;
+ wmb();
+ }
+
return i - 1;
}
@@ -80,6 +129,15 @@ static void menu_reflect(struct cpuidle_device *dev)
if (!(target->flags & CPUIDLE_FLAG_TIME_VALID))
measured_us = USEC_PER_SEC / HZ;
+ if ((target->flags & CPUIDLE_FLAG_DEEP) &&
+ (cpuidle_get_last_residency(dev) < min_deep_sleep)) {
+#if 0
+ printk("F: %d / %d,%d\n", cpuidle_get_last_residency(dev),
+ data->expected_us,data->predicted_us);
+#endif
+ failed_deep++;
+ }
+
/* Predict time remaining until next break event */
if (measured_us + BREAK_FUZZ < data->expected_us - target->exit_latency) {
data->predicted_us = max(measured_us, data->last_measured_us);
@@ -102,7 +160,14 @@ static int menu_enable_device(struct cpuidle_device *dev)
{
struct menu_device *data = &per_cpu(menu_devices, dev->cpu);
+ printk("Attaching menu governor...\n");
+
memset(data, 0, sizeof(struct menu_device));
+ /*
+ * 0 might be slightly ahead of the current jiffies count, so
+ * it's a bad initial value.
+ */
+ data->last_deep = jiffies;
return 0;
}
@@ -121,6 +186,8 @@ static struct cpuidle_governor menu_governor = {
*/
static int __init init_menu(void)
{
+ global_last_deep = jiffies;
+
return cpuidle_register_governor(&menu_governor);
}
@@ -132,6 +199,11 @@ static void __exit exit_menu(void)
cpuidle_unregister_governor(&menu_governor);
}
+module_param(min_deep_sleep, uint, 0644)
+MODULE_PARM_DESC(min_deep_sleep, "min time (us) to spend in deep sleep to avoid noise")
+
+module_param(failed_deep, uint, 0644)
+
MODULE_LICENSE("GPL");
module_init(init_menu);
module_exit(exit_menu);
Rgds
--
-- Pierre Ossman
Linux kernel, MMC maintainer http://www.kernel.org
PulseAudio, core developer http://pulseaudio.org
rdesktop, core developer http://www.rdesktop.org
--
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