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authorIngo Molnar <mingo@elte.hu>2007-08-23 15:18:02 +0200
committerIngo Molnar <mingo@elte.hu>2007-08-23 15:18:02 +0200
commit2aa44d0567ed21b47b87d68819415d48194cb923 (patch)
tree7be2a8a30a23b363e1e2aecd41934e75f581e115 /drivers/acpi
parentb377fd3982ad957c796758a90e2988401a884241 (diff)
sched: sched_clock_idle_[sleep|wakeup]_event()
construct a more or less wall-clock time out of sched_clock(), by using ACPI-idle's existing knowledge about how much time we spent idling. This allows the rq clock to work around TSC-stops-in-C2, TSC-gets-corrupted-in-C3 type of problems. ( Besides the scheduler's statistics this also benefits blktrace and printk-timestamps as well. ) Furthermore, the precise before-C2/C3-sleep and after-C2/C3-wakeup callbacks allow the scheduler to get out the most of the period where the CPU has a reliable TSC. This results in slightly more precise task statistics. the ACPI bits were acked by Len. Signed-off-by: Ingo Molnar <mingo@elte.hu> Acked-by: Len Brown <len.brown@intel.com>
Diffstat (limited to 'drivers/acpi')
-rw-r--r--drivers/acpi/processor_idle.c32
1 files changed, 25 insertions, 7 deletions
diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c
index a8634a0655f..d9b8af763e1 100644
--- a/drivers/acpi/processor_idle.c
+++ b/drivers/acpi/processor_idle.c
@@ -63,6 +63,7 @@
ACPI_MODULE_NAME("processor_idle");
#define ACPI_PROCESSOR_FILE_POWER "power"
#define US_TO_PM_TIMER_TICKS(t) ((t * (PM_TIMER_FREQUENCY/1000)) / 1000)
+#define PM_TIMER_TICK_NS (1000000000ULL/PM_TIMER_FREQUENCY)
#define C2_OVERHEAD 4 /* 1us (3.579 ticks per us) */
#define C3_OVERHEAD 4 /* 1us (3.579 ticks per us) */
static void (*pm_idle_save) (void) __read_mostly;
@@ -462,6 +463,9 @@ static void acpi_processor_idle(void)
* TBD: Can't get time duration while in C1, as resumes
* go to an ISR rather than here. Need to instrument
* base interrupt handler.
+ *
+ * Note: the TSC better not stop in C1, sched_clock() will
+ * skew otherwise.
*/
sleep_ticks = 0xFFFFFFFF;
break;
@@ -469,6 +473,8 @@ static void acpi_processor_idle(void)
case ACPI_STATE_C2:
/* Get start time (ticks) */
t1 = inl(acpi_gbl_FADT.xpm_timer_block.address);
+ /* Tell the scheduler that we are going deep-idle: */
+ sched_clock_idle_sleep_event();
/* Invoke C2 */
acpi_state_timer_broadcast(pr, cx, 1);
acpi_cstate_enter(cx);
@@ -479,17 +485,22 @@ static void acpi_processor_idle(void)
/* TSC halts in C2, so notify users */
mark_tsc_unstable("possible TSC halt in C2");
#endif
+ /* Compute time (ticks) that we were actually asleep */
+ sleep_ticks = ticks_elapsed(t1, t2);
+
+ /* Tell the scheduler how much we idled: */
+ sched_clock_idle_wakeup_event(sleep_ticks*PM_TIMER_TICK_NS);
+
/* Re-enable interrupts */
local_irq_enable();
+ /* Do not account our idle-switching overhead: */
+ sleep_ticks -= cx->latency_ticks + C2_OVERHEAD;
+
current_thread_info()->status |= TS_POLLING;
- /* Compute time (ticks) that we were actually asleep */
- sleep_ticks =
- ticks_elapsed(t1, t2) - cx->latency_ticks - C2_OVERHEAD;
acpi_state_timer_broadcast(pr, cx, 0);
break;
case ACPI_STATE_C3:
-
/*
* disable bus master
* bm_check implies we need ARB_DIS
@@ -518,6 +529,8 @@ static void acpi_processor_idle(void)
t1 = inl(acpi_gbl_FADT.xpm_timer_block.address);
/* Invoke C3 */
acpi_state_timer_broadcast(pr, cx, 1);
+ /* Tell the scheduler that we are going deep-idle: */
+ sched_clock_idle_sleep_event();
acpi_cstate_enter(cx);
/* Get end time (ticks) */
t2 = inl(acpi_gbl_FADT.xpm_timer_block.address);
@@ -531,12 +544,17 @@ static void acpi_processor_idle(void)
/* TSC halts in C3, so notify users */
mark_tsc_unstable("TSC halts in C3");
#endif
+ /* Compute time (ticks) that we were actually asleep */
+ sleep_ticks = ticks_elapsed(t1, t2);
+ /* Tell the scheduler how much we idled: */
+ sched_clock_idle_wakeup_event(sleep_ticks*PM_TIMER_TICK_NS);
+
/* Re-enable interrupts */
local_irq_enable();
+ /* Do not account our idle-switching overhead: */
+ sleep_ticks -= cx->latency_ticks + C3_OVERHEAD;
+
current_thread_info()->status |= TS_POLLING;
- /* Compute time (ticks) that we were actually asleep */
- sleep_ticks =
- ticks_elapsed(t1, t2) - cx->latency_ticks - C3_OVERHEAD;
acpi_state_timer_broadcast(pr, cx, 0);
break;