* [RFC][PATCH] cpuidle: Use nanoseconds as the unit of time
@ 2019-09-05 16:34 Rafael J. Wysocki
2019-09-05 18:07 ` Peter Zijlstra
2019-09-20 16:14 ` Doug Smythies
0 siblings, 2 replies; 3+ messages in thread
From: Rafael J. Wysocki @ 2019-09-05 16:34 UTC (permalink / raw)
To: Linux PM; +Cc: Peter Zijlstra, Daniel Lezcano
From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Currently, the cpuidle subsystem uses microseconds as the unit of
time which (among other things) causes the idle loop to incur some
integer division overhead for no clear benefit.
In order to allow cpuidle to measure time in nanoseconds, add two
additional fields, exit_latency_ns and target_residency_ns, to
represent the exit latency and target residency of an idle state
in nanoseconds, respectively, to struct cpuidle_state_usage and
initialize them with the help of the corresponding valuse in
microseconds provided by drivers. In addition to that, change
cpuidle_governor_latency_req() to return the idle state exit
latency constraint in nanoseconds.
With that, meeasure idle state residency (last_residency_ns in
struct cpuidle_device and time_ns in struct cpuidle_driver) in
nanoseconds and update the cpuidle core and governors accordingly.
However, the menu governor still computes typical intervals in
microseconds to avoid integer overflows.
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
---
Again, not tested yet, posted for feedback mostly, applies on top of
https://patchwork.kernel.org/patch/11129867/
The patch is rather large, but mostly straightforward. There is a rather ugly piece
in the menu governor that first computes the expected idle duration in ns and
then converts it to us just in order to compute the typical interval value, and in
case that is less than the original expected idle duration value, converts it to ns
again. However, if there is a nicer way to do it, I haven't found it so far.
---
drivers/cpuidle/cpuidle.c | 36 +++++------
drivers/cpuidle/driver.c | 29 ++++++---
drivers/cpuidle/governor.c | 7 +-
drivers/cpuidle/governors/haltpoll.c | 7 --
drivers/cpuidle/governors/ladder.c | 25 ++++----
drivers/cpuidle/governors/menu.c | 106 +++++++++++++++++------------------
drivers/cpuidle/governors/teo.c | 72 +++++++++++------------
drivers/cpuidle/sysfs.c | 8 ++
include/linux/cpuidle.h | 8 +-
kernel/sched/idle.c | 2
10 files changed, 158 insertions(+), 142 deletions(-)
Index: linux-pm/include/linux/cpuidle.h
===================================================================
--- linux-pm.orig/include/linux/cpuidle.h
+++ linux-pm/include/linux/cpuidle.h
@@ -35,7 +35,7 @@ struct cpuidle_driver;
struct cpuidle_state_usage {
unsigned long long disable;
unsigned long long usage;
- unsigned long long time; /* in US */
+ u64 time_ns;
unsigned long long above; /* Number of times it's been too deep */
unsigned long long below; /* Number of times it's been too shallow */
#ifdef CONFIG_SUSPEND
@@ -48,6 +48,8 @@ struct cpuidle_state {
char name[CPUIDLE_NAME_LEN];
char desc[CPUIDLE_DESC_LEN];
+ u64 exit_latency_ns;
+ u64 target_residency_ns;
unsigned int flags;
unsigned int exit_latency; /* in US */
int power_usage; /* in mW */
@@ -89,7 +91,7 @@ struct cpuidle_device {
ktime_t next_hrtimer;
int last_state_idx;
- int last_residency;
+ u64 last_residency_ns;
u64 poll_limit_ns;
struct cpuidle_state_usage states_usage[CPUIDLE_STATE_MAX];
struct cpuidle_state_kobj *kobjs[CPUIDLE_STATE_MAX];
@@ -260,7 +262,7 @@ struct cpuidle_governor {
#ifdef CONFIG_CPU_IDLE
extern int cpuidle_register_governor(struct cpuidle_governor *gov);
-extern int cpuidle_governor_latency_req(unsigned int cpu);
+extern s64 cpuidle_governor_latency_req(unsigned int cpu);
#else
static inline int cpuidle_register_governor(struct cpuidle_governor *gov)
{return 0;}
Index: linux-pm/drivers/cpuidle/driver.c
===================================================================
--- linux-pm.orig/drivers/cpuidle/driver.c
+++ linux-pm/drivers/cpuidle/driver.c
@@ -166,16 +166,27 @@ static void __cpuidle_driver_init(struct
if (!drv->cpumask)
drv->cpumask = (struct cpumask *)cpu_possible_mask;
- /*
- * Look for the timer stop flag in the different states, so that we know
- * if the broadcast timer has to be set up. The loop is in the reverse
- * order, because usually one of the deeper states have this flag set.
- */
- for (i = drv->state_count - 1; i >= 0 ; i--) {
- if (drv->states[i].flags & CPUIDLE_FLAG_TIMER_STOP) {
+ for (i = 0; i < drv->state_count; i++) {
+ struct cpuidle_state *s = &drv->states[i];
+
+ /*
+ * Look for the timer stop flag in the different states and if
+ * it is found, indicate that the broadcast timer has to be set
+ * up.
+ */
+ if (s->flags & CPUIDLE_FLAG_TIMER_STOP)
drv->bctimer = 1;
- break;
- }
+
+ /*
+ * The core will use the target residency and exit latency
+ * values in nanoseconds, but allow drivers to provide them in
+ * microseconds too.
+ */
+ if (s->target_residency > 0)
+ s->target_residency_ns = s->target_residency * NSEC_PER_USEC;
+
+ if (s->exit_latency > 0)
+ s->exit_latency_ns = s->exit_latency * NSEC_PER_USEC;
}
}
Index: linux-pm/drivers/cpuidle/cpuidle.c
===================================================================
--- linux-pm.orig/drivers/cpuidle/cpuidle.c
+++ linux-pm/drivers/cpuidle/cpuidle.c
@@ -75,24 +75,24 @@ int cpuidle_play_dead(void)
static int find_deepest_state(struct cpuidle_driver *drv,
struct cpuidle_device *dev,
- unsigned int max_latency,
+ u64 max_latency_ns,
unsigned int forbidden_flags,
bool s2idle)
{
- unsigned int latency_req = 0;
+ u64 latency_req = 0;
int i, ret = 0;
for (i = 1; i < drv->state_count; i++) {
struct cpuidle_state *s = &drv->states[i];
if (dev->states_usage[i].disable ||
- s->exit_latency <= latency_req ||
- s->exit_latency > max_latency ||
+ s->exit_latency_ns <= latency_req ||
+ s->exit_latency_ns > max_latency_ns ||
(s->flags & forbidden_flags) ||
(s2idle && !s->enter_s2idle))
continue;
- latency_req = s->exit_latency;
+ latency_req = s->exit_latency_ns;
ret = i;
}
return ret;
@@ -124,7 +124,7 @@ void cpuidle_use_deepest_state(bool enab
int cpuidle_find_deepest_state(struct cpuidle_driver *drv,
struct cpuidle_device *dev)
{
- return find_deepest_state(drv, dev, UINT_MAX, 0, false);
+ return find_deepest_state(drv, dev, U64_MAX, 0, false);
}
#ifdef CONFIG_SUSPEND
@@ -180,7 +180,7 @@ int cpuidle_enter_s2idle(struct cpuidle_
* that interrupts won't be enabled when it exits and allows the tick to
* be frozen safely.
*/
- index = find_deepest_state(drv, dev, UINT_MAX, 0, true);
+ index = find_deepest_state(drv, dev, U64_MAX, 0, true);
if (index > 0)
enter_s2idle_proper(drv, dev, index);
@@ -209,7 +209,7 @@ int cpuidle_enter_state(struct cpuidle_d
* CPU as a broadcast timer, this call may fail if it is not available.
*/
if (broadcast && tick_broadcast_enter()) {
- index = find_deepest_state(drv, dev, target_state->exit_latency,
+ index = find_deepest_state(drv, dev, target_state->exit_latency_ns,
CPUIDLE_FLAG_TIMER_STOP, false);
if (index < 0) {
default_idle_call();
@@ -247,7 +247,7 @@ int cpuidle_enter_state(struct cpuidle_d
local_irq_enable();
if (entered_state >= 0) {
- s64 diff, delay = drv->states[entered_state].exit_latency;
+ s64 diff, delay = drv->states[entered_state].exit_latency_ns;
int i;
/*
@@ -255,15 +255,13 @@ int cpuidle_enter_state(struct cpuidle_d
* This can be moved to within driver enter routine,
* but that results in multiple copies of same code.
*/
- diff = ktime_us_delta(time_end, time_start);
- if (diff > INT_MAX)
- diff = INT_MAX;
+ diff = ktime_sub(time_end, time_start);
- dev->last_residency = (int)diff;
- dev->states_usage[entered_state].time += dev->last_residency;
+ dev->last_residency_ns = diff;
+ dev->states_usage[entered_state].time_ns += diff;
dev->states_usage[entered_state].usage++;
- if (diff < drv->states[entered_state].target_residency) {
+ if (diff < drv->states[entered_state].target_residency_ns) {
for (i = entered_state - 1; i >= 0; i--) {
if (dev->states_usage[i].disable)
continue;
@@ -281,14 +279,14 @@ int cpuidle_enter_state(struct cpuidle_d
* Update if a deeper state would have been a
* better match for the observed idle duration.
*/
- if (diff - delay >= drv->states[i].target_residency)
+ if (diff - delay >= drv->states[i].target_residency_ns)
dev->states_usage[entered_state].below++;
break;
}
}
} else {
- dev->last_residency = 0;
+ dev->last_residency_ns = 0;
}
return entered_state;
@@ -381,7 +379,7 @@ u64 cpuidle_poll_time(struct cpuidle_dri
if (dev->states_usage[i].disable)
continue;
- limit_ns = (u64)drv->states[i].target_residency * NSEC_PER_USEC;
+ limit_ns = (u64)drv->states[i].target_residency_ns;
}
dev->poll_limit_ns = limit_ns;
@@ -552,7 +550,7 @@ static void __cpuidle_unregister_device(
static void __cpuidle_device_init(struct cpuidle_device *dev)
{
memset(dev->states_usage, 0, sizeof(dev->states_usage));
- dev->last_residency = 0;
+ dev->last_residency_ns = 0;
dev->next_hrtimer = 0;
}
Index: linux-pm/drivers/cpuidle/sysfs.c
===================================================================
--- linux-pm.orig/drivers/cpuidle/sysfs.c
+++ linux-pm/drivers/cpuidle/sysfs.c
@@ -277,13 +277,19 @@ define_show_state_function(exit_latency)
define_show_state_function(target_residency)
define_show_state_function(power_usage)
define_show_state_ull_function(usage)
-define_show_state_ull_function(time)
define_show_state_str_function(name)
define_show_state_str_function(desc)
define_show_state_ull_function(disable)
define_show_state_ull_function(above)
define_show_state_ull_function(below)
+static ssize_t show_state_time(struct cpuidle_state *state,
+ struct cpuidle_state_usage *state_usage,
+ char *buf)
+{
+ return sprintf(buf, "%llu\n", ktime_to_us(state_usage->time_ns));
+}
+
static ssize_t store_state_disable(struct cpuidle_state *state,
struct cpuidle_state_usage *state_usage,
const char *buf, size_t size)
Index: linux-pm/drivers/cpuidle/governor.c
===================================================================
--- linux-pm.orig/drivers/cpuidle/governor.c
+++ linux-pm/drivers/cpuidle/governor.c
@@ -106,11 +106,14 @@ int cpuidle_register_governor(struct cpu
* cpuidle_governor_latency_req - Compute a latency constraint for CPU
* @cpu: Target CPU
*/
-int cpuidle_governor_latency_req(unsigned int cpu)
+s64 cpuidle_governor_latency_req(unsigned int cpu)
{
int global_req = pm_qos_request(PM_QOS_CPU_DMA_LATENCY);
struct device *device = get_cpu_device(cpu);
int device_req = dev_pm_qos_raw_resume_latency(device);
- return device_req < global_req ? device_req : global_req;
+ if (device_req < global_req)
+ device_req = global_req;
+
+ return (s64)device_req * NSEC_PER_USEC;
}
Index: linux-pm/drivers/cpuidle/governors/ladder.c
===================================================================
--- linux-pm.orig/drivers/cpuidle/governors/ladder.c
+++ linux-pm/drivers/cpuidle/governors/ladder.c
@@ -27,8 +27,8 @@ struct ladder_device_state {
struct {
u32 promotion_count;
u32 demotion_count;
- u32 promotion_time;
- u32 demotion_time;
+ u64 promotion_time_ns;
+ u64 demotion_time_ns;
} threshold;
struct {
int promotion_count;
@@ -68,9 +68,10 @@ static int ladder_select_state(struct cp
{
struct ladder_device *ldev = this_cpu_ptr(&ladder_devices);
struct ladder_device_state *last_state;
- int last_residency, last_idx = dev->last_state_idx;
+ int last_idx = dev->last_state_idx;
int first_idx = drv->states[0].flags & CPUIDLE_FLAG_POLLING ? 1 : 0;
- int latency_req = cpuidle_governor_latency_req(dev->cpu);
+ s64 latency_req = cpuidle_governor_latency_req(dev->cpu);
+ s64 last_residency;
/* Special case when user has set very strict latency requirement */
if (unlikely(latency_req == 0)) {
@@ -80,13 +81,13 @@ static int ladder_select_state(struct cp
last_state = &ldev->states[last_idx];
- last_residency = dev->last_residency - drv->states[last_idx].exit_latency;
+ last_residency = dev->last_residency_ns - drv->states[last_idx].exit_latency_ns;
/* consider promotion */
if (last_idx < drv->state_count - 1 &&
!dev->states_usage[last_idx + 1].disable &&
- last_residency > last_state->threshold.promotion_time &&
- drv->states[last_idx + 1].exit_latency <= latency_req) {
+ last_residency > last_state->threshold.promotion_time_ns &&
+ drv->states[last_idx + 1].exit_latency_ns <= latency_req) {
last_state->stats.promotion_count++;
last_state->stats.demotion_count = 0;
if (last_state->stats.promotion_count >= last_state->threshold.promotion_count) {
@@ -98,11 +99,11 @@ static int ladder_select_state(struct cp
/* consider demotion */
if (last_idx > first_idx &&
(dev->states_usage[last_idx].disable ||
- drv->states[last_idx].exit_latency > latency_req)) {
+ drv->states[last_idx].exit_latency_ns > latency_req)) {
int i;
for (i = last_idx - 1; i > first_idx; i--) {
- if (drv->states[i].exit_latency <= latency_req)
+ if (drv->states[i].exit_latency_ns <= latency_req)
break;
}
ladder_do_selection(dev, ldev, last_idx, i);
@@ -110,7 +111,7 @@ static int ladder_select_state(struct cp
}
if (last_idx > first_idx &&
- last_residency < last_state->threshold.demotion_time) {
+ last_residency < last_state->threshold.demotion_time_ns) {
last_state->stats.demotion_count++;
last_state->stats.promotion_count = 0;
if (last_state->stats.demotion_count >= last_state->threshold.demotion_count) {
@@ -150,9 +151,9 @@ static int ladder_enable_device(struct c
lstate->threshold.demotion_count = DEMOTION_COUNT;
if (i < drv->state_count - 1)
- lstate->threshold.promotion_time = state->exit_latency;
+ lstate->threshold.promotion_time_ns = state->exit_latency_ns;
if (i > first_idx)
- lstate->threshold.demotion_time = state->exit_latency;
+ lstate->threshold.demotion_time_ns = state->exit_latency_ns;
}
return 0;
Index: linux-pm/drivers/cpuidle/governors/menu.c
===================================================================
--- linux-pm.orig/drivers/cpuidle/governors/menu.c
+++ linux-pm/drivers/cpuidle/governors/menu.c
@@ -33,7 +33,7 @@
#define INTERVALS (1UL << INTERVAL_SHIFT)
#define RESOLUTION 1024
#define DECAY 8
-#define MAX_INTERESTING 50000
+#define MAX_INTERESTING (50000 * NSEC_PER_USEC)
/*
@@ -120,14 +120,14 @@ struct menu_device {
int needs_update;
int tick_wakeup;
- unsigned int next_timer_us;
+ u64 next_timer_ns;
unsigned int bucket;
unsigned int correction_factor[BUCKETS];
unsigned int intervals[INTERVALS];
int interval_ptr;
};
-static inline int which_bucket(unsigned int duration, unsigned long nr_iowaiters)
+static inline int which_bucket(u64 duration_ns, unsigned long nr_iowaiters)
{
int bucket = 0;
@@ -140,15 +140,15 @@ static inline int which_bucket(unsigned
if (nr_iowaiters)
bucket = BUCKETS/2;
- if (duration < 10)
+ if (duration_ns < 10ULL * NSEC_PER_USEC)
return bucket;
- if (duration < 100)
+ if (duration_ns < 100ULL * NSEC_PER_USEC)
return bucket + 1;
- if (duration < 1000)
+ if (duration_ns < 1000ULL * NSEC_PER_USEC)
return bucket + 2;
- if (duration < 10000)
+ if (duration_ns < 10000ULL * NSEC_PER_USEC)
return bucket + 3;
- if (duration < 100000)
+ if (duration_ns < 100000ULL * NSEC_PER_USEC)
return bucket + 4;
return bucket + 5;
}
@@ -276,11 +276,12 @@ static int menu_select(struct cpuidle_dr
bool *stop_tick)
{
struct menu_device *data = this_cpu_ptr(&menu_devices);
- int latency_req = cpuidle_governor_latency_req(dev->cpu);
+ s64 latency_req = cpuidle_governor_latency_req(dev->cpu);
int i;
int idx;
- unsigned int interactivity_req;
- unsigned int predicted_us;
+ u64 predicted_ns;
+ unsigned int predicted_us, typical_us;
+ u64 interactivity_req;
unsigned long nr_iowaiters;
ktime_t delta_next;
@@ -290,14 +291,14 @@ static int menu_select(struct cpuidle_dr
}
/* determine the expected residency time, round up */
- data->next_timer_us = ktime_to_us(tick_nohz_get_sleep_length(&delta_next));
+ data->next_timer_ns = tick_nohz_get_sleep_length(&delta_next);
nr_iowaiters = nr_iowait_cpu(dev->cpu);
- data->bucket = which_bucket(data->next_timer_us, nr_iowaiters);
+ data->bucket = which_bucket(data->next_timer_ns, nr_iowaiters);
if (unlikely(drv->state_count <= 1 || latency_req == 0) ||
- ((data->next_timer_us < drv->states[1].target_residency ||
- latency_req < drv->states[1].exit_latency) &&
+ ((data->next_timer_ns < drv->states[1].target_residency_ns ||
+ latency_req < drv->states[1].exit_latency_ns) &&
!dev->states_usage[0].disable)) {
/*
* In this case state[0] will be used no matter what, so return
@@ -308,18 +309,18 @@ static int menu_select(struct cpuidle_dr
return 0;
}
- /*
- * Force the result of multiplication to be 64 bits even if both
- * operands are 32 bits.
- * Make sure to round up for half microseconds.
- */
- predicted_us = DIV_ROUND_CLOSEST_ULL((uint64_t)data->next_timer_us *
- data->correction_factor[data->bucket],
- RESOLUTION * DECAY);
+ predicted_ns = div64_u64(data->next_timer_ns *
+ data->correction_factor[data->bucket],
+ RESOLUTION * DECAY);
+ predicted_us = ktime_to_us(predicted_ns);
/*
* Use the lowest expected idle interval to pick the idle state.
*/
- predicted_us = min(predicted_us, get_typical_interval(data, predicted_us));
+ typical_us = get_typical_interval(data, predicted_us);
+ if (typical_us < predicted_us) {
+ predicted_us = typical_us;
+ predicted_ns = (u64)typical_us * NSEC_PER_USEC;
+ }
if (tick_nohz_tick_stopped()) {
/*
@@ -330,14 +331,15 @@ static int menu_select(struct cpuidle_dr
* the known time till the closest timer event for the idle
* state selection.
*/
- if (predicted_us < TICK_USEC)
- predicted_us = ktime_to_us(delta_next);
+ if (predicted_ns < TICK_NSEC)
+ predicted_ns = delta_next;
} else {
/*
* Use the performance multiplier and the user-configurable
* latency_req to determine the maximum exit latency.
*/
- interactivity_req = predicted_us / performance_multiplier(nr_iowaiters);
+ interactivity_req = div64_u64(predicted_ns,
+ performance_multiplier(nr_iowaiters));
if (latency_req > interactivity_req)
latency_req = interactivity_req;
}
@@ -356,15 +358,15 @@ static int menu_select(struct cpuidle_dr
if (idx == -1)
idx = i; /* first enabled state */
- if (s->target_residency > predicted_us) {
+ if (s->target_residency_ns > predicted_ns) {
/*
* Use a physical idle state, not busy polling, unless
* a timer is going to trigger soon enough.
*/
if ((drv->states[idx].flags & CPUIDLE_FLAG_POLLING) &&
- s->exit_latency <= latency_req &&
- s->target_residency <= data->next_timer_us) {
- predicted_us = s->target_residency;
+ s->exit_latency_ns <= latency_req &&
+ s->target_residency_ns <= data->next_timer_ns) {
+ predicted_ns = s->target_residency_ns;
idx = i;
break;
}
@@ -378,7 +380,7 @@ static int menu_select(struct cpuidle_dr
* tick in that case and let the governor run
* again in the next iteration of the loop.
*/
- predicted_us = drv->states[idx].target_residency;
+ predicted_ns = drv->states[idx].target_residency_ns;
break;
}
@@ -388,13 +390,13 @@ static int menu_select(struct cpuidle_dr
* closest timer event, select this one to avoid getting
* stuck in the shallow one for too long.
*/
- if (drv->states[idx].target_residency < TICK_USEC &&
- s->target_residency <= ktime_to_us(delta_next))
+ if (drv->states[idx].target_residency_ns < TICK_NSEC &&
+ s->target_residency_ns <= delta_next)
idx = i;
return idx;
}
- if (s->exit_latency > latency_req)
+ if (s->exit_latency_ns > latency_req_ns)
break;
idx = i;
@@ -408,12 +410,10 @@ static int menu_select(struct cpuidle_dr
* expected idle duration is shorter than the tick period length.
*/
if (((drv->states[idx].flags & CPUIDLE_FLAG_POLLING) ||
- predicted_us < TICK_USEC) && !tick_nohz_tick_stopped()) {
- unsigned int delta_next_us = ktime_to_us(delta_next);
-
+ predicted_ns < TICK_NSEC) && !tick_nohz_tick_stopped()) {
*stop_tick = false;
- if (idx > 0 && drv->states[idx].target_residency > delta_next_us) {
+ if (idx > 0 && drv->states[idx].target_residency_ns > delta_next) {
/*
* The tick is not going to be stopped and the target
* residency of the state to be returned is not within
@@ -425,7 +425,7 @@ static int menu_select(struct cpuidle_dr
continue;
idx = i;
- if (drv->states[i].target_residency <= delta_next_us)
+ if (drv->states[i].target_residency_ns <= delta_next)
break;
}
}
@@ -461,7 +461,7 @@ static void menu_update(struct cpuidle_d
struct menu_device *data = this_cpu_ptr(&menu_devices);
int last_idx = dev->last_state_idx;
struct cpuidle_state *target = &drv->states[last_idx];
- unsigned int measured_us;
+ u64 measured_ns;
unsigned int new_factor;
/*
@@ -479,7 +479,7 @@ static void menu_update(struct cpuidle_d
* assume the state was never reached and the exit latency is 0.
*/
- if (data->tick_wakeup && data->next_timer_us > TICK_USEC) {
+ if (data->tick_wakeup && data->next_timer_ns > TICK_NSEC) {
/*
* The nohz code said that there wouldn't be any events within
* the tick boundary (if the tick was stopped), but the idle
@@ -489,7 +489,7 @@ static void menu_update(struct cpuidle_d
* have been idle long (but not forever) to help the idle
* duration predictor do a better job next time.
*/
- measured_us = 9 * MAX_INTERESTING / 10;
+ measured_ns = 9 * MAX_INTERESTING / 10;
} else if ((drv->states[last_idx].flags & CPUIDLE_FLAG_POLLING) &&
dev->poll_time_limit) {
/*
@@ -499,28 +499,28 @@ static void menu_update(struct cpuidle_d
* the CPU might have been woken up from idle by the next timer.
* Assume that to be the case.
*/
- measured_us = data->next_timer_us;
+ measured_ns = data->next_timer_ns;
} else {
/* measured value */
- measured_us = dev->last_residency;
+ measured_ns = dev->last_residency_ns;
/* Deduct exit latency */
- if (measured_us > 2 * target->exit_latency)
- measured_us -= target->exit_latency;
+ if (measured_ns > 2 * target->exit_latency_ns)
+ measured_ns -= target->exit_latency_ns;
else
- measured_us /= 2;
+ measured_ns /= 2;
}
/* Make sure our coefficients do not exceed unity */
- if (measured_us > data->next_timer_us)
- measured_us = data->next_timer_us;
+ if (measured_ns > data->next_timer_ns)
+ measured_ns = data->next_timer_ns;
/* Update our correction ratio */
new_factor = data->correction_factor[data->bucket];
new_factor -= new_factor / DECAY;
- if (data->next_timer_us > 0 && measured_us < MAX_INTERESTING)
- new_factor += RESOLUTION * measured_us / data->next_timer_us;
+ if (data->next_timer_ns > 0 && measured_ns < MAX_INTERESTING)
+ new_factor += RESOLUTION * div64_u64(measured_ns, data->next_timer_ns);
else
/*
* we were idle so long that we count it as a perfect
@@ -540,7 +540,7 @@ static void menu_update(struct cpuidle_d
data->correction_factor[data->bucket] = new_factor;
/* update the repeating-pattern data */
- data->intervals[data->interval_ptr++] = measured_us;
+ data->intervals[data->interval_ptr++] = ktime_to_us(measured_ns);
if (data->interval_ptr >= INTERVALS)
data->interval_ptr = 0;
}
Index: linux-pm/drivers/cpuidle/governors/teo.c
===================================================================
--- linux-pm.orig/drivers/cpuidle/governors/teo.c
+++ linux-pm/drivers/cpuidle/governors/teo.c
@@ -104,7 +104,7 @@ struct teo_cpu {
u64 sleep_length_ns;
struct teo_idle_state states[CPUIDLE_STATE_MAX];
int interval_idx;
- unsigned int intervals[INTERVALS];
+ u64 intervals[INTERVALS];
};
static DEFINE_PER_CPU(struct teo_cpu, teo_cpus);
@@ -117,9 +117,8 @@ static DEFINE_PER_CPU(struct teo_cpu, te
static void teo_update(struct cpuidle_driver *drv, struct cpuidle_device *dev)
{
struct teo_cpu *cpu_data = per_cpu_ptr(&teo_cpus, dev->cpu);
- unsigned int sleep_length_us = ktime_to_us(cpu_data->sleep_length_ns);
int i, idx_hit = -1, idx_timer = -1;
- unsigned int measured_us;
+ u64 measured_ns;
if (cpu_data->time_span_ns >= cpu_data->sleep_length_ns) {
/*
@@ -127,23 +126,21 @@ static void teo_update(struct cpuidle_dr
* enough to the closest timer event expected at the idle state
* selection time to be discarded.
*/
- measured_us = UINT_MAX;
+ measured_ns = U64_MAX;
} else {
- unsigned int lat;
+ u64 lat_ns = drv->states[dev->last_state_idx].exit_latency_ns;
- lat = drv->states[dev->last_state_idx].exit_latency;
-
- measured_us = ktime_to_us(cpu_data->time_span_ns);
+ measured_ns = cpu_data->time_span_ns;
/*
* The delay between the wakeup and the first instruction
* executed by the CPU is not likely to be worst-case every
* time, so take 1/2 of the exit latency as a very rough
* approximation of the average of it.
*/
- if (measured_us >= lat)
- measured_us -= lat / 2;
+ if (measured_ns >= lat_ns)
+ measured_ns -= lat_ns / 2;
else
- measured_us /= 2;
+ measured_ns /= 2;
}
/*
@@ -155,9 +152,9 @@ static void teo_update(struct cpuidle_dr
cpu_data->states[i].early_hits -= early_hits >> DECAY_SHIFT;
- if (drv->states[i].target_residency <= sleep_length_us) {
+ if (drv->states[i].target_residency_ns <= cpu_data->sleep_length_ns) {
idx_timer = i;
- if (drv->states[i].target_residency <= measured_us)
+ if (drv->states[i].target_residency_ns <= measured_ns)
idx_hit = i;
}
}
@@ -193,7 +190,7 @@ static void teo_update(struct cpuidle_dr
* Save idle duration values corresponding to non-timer wakeups for
* pattern detection.
*/
- cpu_data->intervals[cpu_data->interval_idx++] = measured_us;
+ cpu_data->intervals[cpu_data->interval_idx++] = measured_ns;
if (cpu_data->interval_idx > INTERVALS)
cpu_data->interval_idx = 0;
}
@@ -203,11 +200,11 @@ static void teo_update(struct cpuidle_dr
* @drv: cpuidle driver containing state data.
* @dev: Target CPU.
* @state_idx: Index of the capping idle state.
- * @duration_us: Idle duration value to match.
+ * @duration_ns: Idle duration value to match.
*/
static int teo_find_shallower_state(struct cpuidle_driver *drv,
struct cpuidle_device *dev, int state_idx,
- unsigned int duration_us)
+ u64 duration_ns)
{
int i;
@@ -216,7 +213,7 @@ static int teo_find_shallower_state(stru
continue;
state_idx = i;
- if (drv->states[i].target_residency <= duration_us)
+ if (drv->states[i].target_residency_ns <= duration_ns)
break;
}
return state_idx;
@@ -232,8 +229,9 @@ static int teo_select(struct cpuidle_dri
bool *stop_tick)
{
struct teo_cpu *cpu_data = per_cpu_ptr(&teo_cpus, dev->cpu);
- int latency_req = cpuidle_governor_latency_req(dev->cpu);
- unsigned int duration_us, count;
+ s64 latency_req = cpuidle_governor_latency_req(dev->cpu);
+ u64 duration_ns;
+ unsigned int count;
int max_early_idx, constraint_idx, idx, i;
ktime_t delta_tick;
@@ -244,8 +242,8 @@ static int teo_select(struct cpuidle_dri
cpu_data->time_span_ns = local_clock();
- cpu_data->sleep_length_ns = tick_nohz_get_sleep_length(&delta_tick);
- duration_us = ktime_to_us(cpu_data->sleep_length_ns);
+ duration_ns = tick_nohz_get_sleep_length(&delta_tick);
+ cpu_data->sleep_length_ns = duration_ns;
count = 0;
max_early_idx = -1;
@@ -275,17 +273,17 @@ static int teo_select(struct cpuidle_dri
if (idx < 0)
idx = i; /* first enabled state */
- if (s->target_residency > duration_us)
+ if (s->target_residency_ns > duration_ns)
break;
- if (s->exit_latency > latency_req && constraint_idx > i)
+ if (s->exit_latency_ns > latency_req && constraint_idx > i)
constraint_idx = i;
idx = i;
if (count < cpu_data->states[i].early_hits &&
!(tick_nohz_tick_stopped() &&
- drv->states[i].target_residency < TICK_USEC)) {
+ drv->states[i].target_residency_ns < TICK_NSEC)) {
count = cpu_data->states[i].early_hits;
max_early_idx = i;
}
@@ -302,7 +300,7 @@ static int teo_select(struct cpuidle_dri
if (cpu_data->states[idx].hits <= cpu_data->states[idx].misses &&
max_early_idx >= 0) {
idx = max_early_idx;
- duration_us = drv->states[idx].target_residency;
+ duration_ns = drv->states[idx].target_residency_ns;
}
/*
@@ -324,9 +322,9 @@ static int teo_select(struct cpuidle_dri
* the current expected idle duration value.
*/
for (i = 0; i < INTERVALS; i++) {
- unsigned int val = cpu_data->intervals[i];
+ u64 val = cpu_data->intervals[i];
- if (val >= duration_us)
+ if (val >= duration_ns)
continue;
count++;
@@ -338,17 +336,17 @@ static int teo_select(struct cpuidle_dri
* values are in the interesting range.
*/
if (count > INTERVALS / 2) {
- unsigned int avg_us = div64_u64(sum, count);
+ u64 avg_ns = div64_u64(sum, count);
/*
* Avoid spending too much time in an idle state that
* would be too shallow.
*/
- if (!(tick_nohz_tick_stopped() && avg_us < TICK_USEC)) {
- duration_us = avg_us;
- if (drv->states[idx].target_residency > avg_us)
+ if (!(tick_nohz_tick_stopped() && avg_ns < TICK_NSEC)) {
+ duration_ns = avg_ns;
+ if (drv->states[idx].target_residency_ns > avg_ns)
idx = teo_find_shallower_state(drv, dev,
- idx, avg_us);
+ idx, avg_ns);
}
}
}
@@ -358,9 +356,7 @@ static int teo_select(struct cpuidle_dri
* expected idle duration is shorter than the tick period length.
*/
if (((drv->states[idx].flags & CPUIDLE_FLAG_POLLING) ||
- duration_us < TICK_USEC) && !tick_nohz_tick_stopped()) {
- unsigned int delta_tick_us = ktime_to_us(delta_tick);
-
+ duration_ns < TICK_NSEC) && !tick_nohz_tick_stopped()) {
*stop_tick = false;
/*
@@ -369,8 +365,8 @@ static int teo_select(struct cpuidle_dri
* till the closest timer including the tick, try to correct
* that.
*/
- if (idx > 0 && drv->states[idx].target_residency > delta_tick_us)
- idx = teo_find_shallower_state(drv, dev, idx, delta_tick_us);
+ if (idx > 0 && drv->states[idx].target_residency_ns > delta_tick)
+ idx = teo_find_shallower_state(drv, dev, idx, delta_tick);
}
return idx;
@@ -414,7 +410,7 @@ static int teo_enable_device(struct cpui
memset(cpu_data, 0, sizeof(*cpu_data));
for (i = 0; i < INTERVALS; i++)
- cpu_data->intervals[i] = UINT_MAX;
+ cpu_data->intervals[i] = U64_MAX;
return 0;
}
Index: linux-pm/drivers/cpuidle/governors/haltpoll.c
===================================================================
--- linux-pm.orig/drivers/cpuidle/governors/haltpoll.c
+++ linux-pm/drivers/cpuidle/governors/haltpoll.c
@@ -49,7 +49,7 @@ static int haltpoll_select(struct cpuidl
struct cpuidle_device *dev,
bool *stop_tick)
{
- int latency_req = cpuidle_governor_latency_req(dev->cpu);
+ s64 latency_req = cpuidle_governor_latency_req(dev->cpu);
if (!drv->state_count || latency_req == 0) {
*stop_tick = false;
@@ -75,10 +75,9 @@ static int haltpoll_select(struct cpuidl
return 0;
}
-static void adjust_poll_limit(struct cpuidle_device *dev, unsigned int block_us)
+static void adjust_poll_limit(struct cpuidle_device *dev, u64 block_ns)
{
unsigned int val;
- u64 block_ns = block_us*NSEC_PER_USEC;
/* Grow cpu_halt_poll_us if
* cpu_halt_poll_us < block_ns < guest_halt_poll_us
@@ -115,7 +114,7 @@ static void haltpoll_reflect(struct cpui
dev->last_state_idx = index;
if (index != 0)
- adjust_poll_limit(dev, dev->last_residency);
+ adjust_poll_limit(dev, dev->last_residency_ns);
}
/**
Index: linux-pm/kernel/sched/idle.c
===================================================================
--- linux-pm.orig/kernel/sched/idle.c
+++ linux-pm/kernel/sched/idle.c
@@ -104,7 +104,7 @@ static int call_cpuidle(struct cpuidle_d
* update no idle residency and return.
*/
if (current_clr_polling_and_test()) {
- dev->last_residency = 0;
+ dev->last_residency_ns = 0;
local_irq_enable();
return -EBUSY;
}
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [RFC][PATCH] cpuidle: Use nanoseconds as the unit of time
2019-09-05 16:34 [RFC][PATCH] cpuidle: Use nanoseconds as the unit of time Rafael J. Wysocki
@ 2019-09-05 18:07 ` Peter Zijlstra
2019-09-20 16:14 ` Doug Smythies
1 sibling, 0 replies; 3+ messages in thread
From: Peter Zijlstra @ 2019-09-05 18:07 UTC (permalink / raw)
To: Rafael J. Wysocki; +Cc: Linux PM, Daniel Lezcano
On Thu, Sep 05, 2019 at 06:34:49PM +0200, Rafael J. Wysocki wrote:
> The patch is rather large, but mostly straightforward. There is a rather ugly piece
> in the menu governor that first computes the expected idle duration in ns and
> then converts it to us just in order to compute the typical interval value, and in
> case that is less than the original expected idle duration value, converts it to ns
> again. However, if there is a nicer way to do it, I haven't found it so far.
predicted_ns = div64_u64(data->next_timer_ns *
data->correction_factor[data->bucket],
RESOLUTION * DECAY);
predicted_us = ktime_to_us(predicted_ns);
/*
* Use the lowest expected idle interval to pick the idle state.
*/
typical_us = get_typical_interval(data, predicted_us);
if (typical_us < predicted_us) {
predicted_us = typical_us;
predicted_ns = (u64)typical_us * NSEC_PER_USEC;
}
Yeah, that is a bit yuck.
The first part:
predicted_ns = div64_u64(data->next_timer_ns *
data->correction_factor[data->bucket],
RESOLUTION * DECAY);
predicted_us = ktime_to_us(predicted_ns);
can of course be written like:
predicted_us = div_u64(data->next_timer_ns * data->correction_factor[data->bucket],
RESOLUTION * DECAY * NSEC_PER_USEC);
Since RESOLUTION * DECAY * NSEC_PER_USEC is only 8e6, that doesn't need
to be a u64, so u64 / u32 is sufficient and cheaper.
(looking at the original, you did loose the ROUND_CLOSEST bit, which can
trivially be restored like:
predicted_us = div_u64(data->next_timer_ns * data->correction_factor[data->bucket] +
(RESOLUTION * DECAY * NSEC_PER_USEC) / 2, RESOLUTION * DECAY * NSEC_PER_USEC);
So that reduces from: u64/u64 + u64/32 to u64/32, which should be lots
on 32bit.
After that it then becomes:
predicted_ns = (u64)min(predicted_us, get_typical_interval(data, predicted_us)) * NSEC_PER_USEC;
Which is an unconditional multiplication with a constant, which is loads
better than divisions.
Granted, it's still not pretty, but it should be faster than it was.
(this all assumes the initial multiplication doesn't overflow due to now
using ->next_timer_ns of course)
^ permalink raw reply [flat|nested] 3+ messages in thread
* RE: [RFC][PATCH] cpuidle: Use nanoseconds as the unit of time
2019-09-05 16:34 [RFC][PATCH] cpuidle: Use nanoseconds as the unit of time Rafael J. Wysocki
2019-09-05 18:07 ` Peter Zijlstra
@ 2019-09-20 16:14 ` Doug Smythies
1 sibling, 0 replies; 3+ messages in thread
From: Doug Smythies @ 2019-09-20 16:14 UTC (permalink / raw)
To: 'Rafael J. Wysocki'
Cc: 'Peter Zijlstra', 'Daniel Lezcano', 'Linux PM'
Hi Rafael,
To be able to try this patch (and the idle disable consolidation one),
I simply waited until it would apply properly in the main git tree, which it now does.
However it does not compile:
On 2019.09.05 09:35 Rafael J. Wysocki wrote:
...
> In addition to that, change
> cpuidle_governor_latency_req() to return the idle state exit
> latency constraint in nanoseconds.
...
> Index: linux-pm/drivers/cpuidle/governors/menu.c
...
> @@ -388,13 +390,13 @@ static int menu_select(struct cpuidle_dr
> * closest timer event, select this one to avoid getting
> * stuck in the shallow one for too long.
> */
> - if (drv->states[idx].target_residency < TICK_USEC &&
> - s->target_residency <= ktime_to_us(delta_next))
> + if (drv->states[idx].target_residency_ns < TICK_NSEC &&
> + s->target_residency_ns <= delta_next)
> idx = i;
>
> return idx;
> }
> - if (s->exit_latency > latency_req)
> + if (s->exit_latency_ns > latency_req_ns)
^^^^^^^^^^^^^^^
Should be (I think):
+ if (s->exit_latency_ns > latency_req)
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2019-09-20 16:15 UTC | newest]
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2019-09-05 16:34 [RFC][PATCH] cpuidle: Use nanoseconds as the unit of time Rafael J. Wysocki
2019-09-05 18:07 ` Peter Zijlstra
2019-09-20 16:14 ` Doug Smythies
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