Mailing List Archive

# HG changeset patch
# User Keir Fraser <keir.fraser@citrix.com>
# Date 1276761085 -3600
# Node ID 919ffe9b60b543c9bb0baae450d994904635b708
# Parent 6fffbb86acae27f5a742884b5d3b5a5c73b4ed15
cpuidle: use stime to count c-state residency in NONSTOP_TSC case

stime is based on tsc, with far less access cost than PM timer. So for
processors w/ NONSTOP_TSC, using stime instead of PM timer. This could
reduce idle overheads and save power.

Signed-off-by: Wei Gang <gang.wei@intel.com>
---
xen/arch/x86/acpi/cpu_idle.c | 51 +++++++++++++++++++++++++++++++++----------
1 files changed, 40 insertions(+), 11 deletions(-)

diff -r 6fffbb86acae -r 919ffe9b60b5 xen/arch/x86/acpi/cpu_idle.c
--- a/xen/arch/x86/acpi/cpu_idle.c Thu Jun 17 08:50:55 2010 +0100
+++ b/xen/arch/x86/acpi/cpu_idle.c Thu Jun 17 08:51:25 2010 +0100
@@ -59,6 +59,11 @@ static void (*lapic_timer_off)(void);
static void (*lapic_timer_off)(void);
static void (*lapic_timer_on)(void);

+static uint64_t (*get_tick)(void);
+static uint64_t (*ticks_elapsed)(uint64_t t1, uint64_t t2);
+static uint64_t (*tick_to_ns)(uint64_t ticks);
+static uint64_t (*ns_to_tick)(uint64_t ticks);
+
extern void (*pm_idle) (void);
extern void (*dead_idle) (void);
extern void menu_get_trace_data(u32 *expected, u32 *pred);
@@ -92,7 +97,7 @@ static void print_acpi_power(uint32_t cp

for ( i = 1; i < power->count; i++ )
{
- res = acpi_pm_tick_to_ns(power->states[i].time);
+ res = tick_to_ns(power->states[i].time);
idle_usage += power->states[i].usage;
idle_res += res;

@@ -133,7 +138,13 @@ static int __init cpu_idle_key_init(void
}
__initcall(cpu_idle_key_init);

-static inline u32 ticks_elapsed(u32 t1, u32 t2)
+static uint64_t get_stime_tick(void) { return (uint64_t)NOW(); }
+static uint64_t stime_ticks_elapsed(uint64_t t1, uint64_t t2) { return t2 - t1; }
+static uint64_t stime_tick_to_ns(uint64_t ticks) { return ticks; }
+static uint64_t ns_to_stime_tick(uint64_t ns) { return ns; }
+
+static uint64_t get_acpi_pm_tick(void) { return (uint64_t)inl(pmtmr_ioport); }
+static uint64_t acpi_pm_ticks_elapsed(uint64_t t1, uint64_t t2)
{
if ( t2 >= t1 )
return (t2 - t1);
@@ -279,8 +290,8 @@ static void acpi_processor_idle(void)
struct acpi_processor_power *power = processor_powers[smp_processor_id()];
struct acpi_processor_cx *cx = NULL;
int next_state;
- int sleep_ticks = 0;
- u32 t1, t2 = 0;
+ int64_t sleep_ticks = 0;
+ uint64_t t1, t2 = 0;
u32 exp = 0, pred = 0;
u32 irq_traced[4] = { 0 };

@@ -338,13 +349,13 @@ static void acpi_processor_idle(void)
if ( cx->type == ACPI_STATE_C1 || local_apic_timer_c2_ok )
{
/* Get start time (ticks) */
- t1 = inl(pmtmr_ioport);
+ t1 = get_tick();
/* Trace cpu idle entry */
TRACE_4D(TRC_PM_IDLE_ENTRY, cx->idx, t1, exp, pred);
/* Invoke C2 */
acpi_idle_do_entry(cx);
/* Get end time (ticks) */
- t2 = inl(pmtmr_ioport);
+ t2 = get_tick();
trace_exit_reason(irq_traced);
/* Trace cpu idle exit */
TRACE_6D(TRC_PM_IDLE_EXIT, cx->idx, t2,
@@ -395,13 +406,13 @@ static void acpi_processor_idle(void)
lapic_timer_off();

/* Get start time (ticks) */
- t1 = inl(pmtmr_ioport);
+ t1 = get_tick();
/* Trace cpu idle entry */
TRACE_4D(TRC_PM_IDLE_ENTRY, cx->idx, t1, exp, pred);
/* Invoke C3 */
acpi_idle_do_entry(cx);
/* Get end time (ticks) */
- t2 = inl(pmtmr_ioport);
+ t2 = get_tick();

/* recovering TSC */
cstate_restore_tsc();
@@ -438,7 +449,7 @@ static void acpi_processor_idle(void)
cx->usage++;
if ( sleep_ticks > 0 )
{
- power->last_residency = acpi_pm_tick_to_ns(sleep_ticks) / 1000UL;
+ power->last_residency = tick_to_ns(sleep_ticks) / 1000UL;
cx->time += sleep_ticks;
}

@@ -751,7 +762,7 @@ static void set_cx(
cx->latency = xen_cx->latency;
cx->power = xen_cx->power;

- cx->latency_ticks = ns_to_acpi_pm_tick(cx->latency * 1000UL);
+ cx->latency_ticks = ns_to_tick(cx->latency * 1000UL);
cx->target_residency = cx->latency * latency_factor;
if ( cx->type == ACPI_STATE_C1 || cx->type == ACPI_STATE_C2 )
acpi_power->safe_state = cx;
@@ -845,6 +856,24 @@ long set_cx_pminfo(uint32_t cpu, struct
return -EFAULT;
}

+ if ( cpu_id == 0 )
+ {
+ if ( boot_cpu_has(X86_FEATURE_NONSTOP_TSC) )
+ {
+ get_tick = get_stime_tick;
+ ticks_elapsed = stime_ticks_elapsed;
+ tick_to_ns = stime_tick_to_ns;
+ ns_to_tick = ns_to_stime_tick;
+ }
+ else
+ {
+ get_tick = get_acpi_pm_tick;
+ ticks_elapsed = acpi_pm_ticks_elapsed;
+ tick_to_ns = acpi_pm_tick_to_ns;
+ ns_to_tick = ns_to_acpi_pm_tick;
+ }
+ }
+
acpi_power = processor_powers[cpu_id];
if ( !acpi_power )
{
@@ -922,7 +951,7 @@ int pmstat_get_cx_stat(uint32_t cpuid, s
if ( i != 0 )
{
usage = power->states[i].usage;
- res = acpi_pm_tick_to_ns(power->states[i].time);
+ res = tick_to_ns(power->states[i].time);
idle_usage += usage;
idle_res += res;
}

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