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/**
* \file
* native threadpool worker
*
* Author:
* Ludovic Henry (ludovic.henry@xamarin.com)
*
* Licensed under the MIT license. See LICENSE file in the project root for full license information.
*/
#include <stdlib.h>
#define _USE_MATH_DEFINES // needed by MSVC to define math constants
#include <math.h>
#include <config.h>
#include <glib.h>
#include <mono/metadata/class-internals.h>
#include <mono/metadata/exception.h>
#include <mono/metadata/gc-internals.h>
#include <mono/metadata/object.h>
#include <mono/metadata/object-internals.h>
#include <mono/metadata/threadpool.h>
#include <mono/metadata/threadpool-worker.h>
#include <mono/metadata/threadpool-io.h>
#include <mono/metadata/w32event.h>
#include <mono/utils/atomic.h>
#include <mono/utils/mono-compiler.h>
#include <mono/utils/mono-complex.h>
#include <mono/utils/mono-logger.h>
#include <mono/utils/mono-logger-internals.h>
#include <mono/utils/mono-proclib.h>
#include <mono/utils/mono-threads.h>
#include <mono/utils/mono-time.h>
#include <mono/utils/mono-rand.h>
#include <mono/utils/refcount.h>
#include <mono/utils/w32api.h>
#define CPU_USAGE_LOW 80
#define CPU_USAGE_HIGH 95
#define MONITOR_INTERVAL 500 // ms
#define MONITOR_MINIMAL_LIFETIME 60 * 1000 // ms
#define WORKER_CREATION_MAX_PER_SEC 10
/* The exponent to apply to the gain. 1.0 means to use linear gain,
* higher values will enhance large moves and damp small ones.
* default: 2.0 */
#define HILL_CLIMBING_GAIN_EXPONENT 2.0
/* The 'cost' of a thread. 0 means drive for increased throughput regardless
* of thread count, higher values bias more against higher thread counts.
* default: 0.15 */
#define HILL_CLIMBING_BIAS 0.15
#define HILL_CLIMBING_WAVE_PERIOD 4
#define HILL_CLIMBING_MAX_WAVE_MAGNITUDE 20
#define HILL_CLIMBING_WAVE_MAGNITUDE_MULTIPLIER 1.0
#define HILL_CLIMBING_WAVE_HISTORY_SIZE 8
#define HILL_CLIMBING_TARGET_SIGNAL_TO_NOISE_RATIO 3.0
#define HILL_CLIMBING_MAX_CHANGE_PER_SECOND 4
#define HILL_CLIMBING_MAX_CHANGE_PER_SAMPLE 20
#define HILL_CLIMBING_SAMPLE_INTERVAL_LOW 10
#define HILL_CLIMBING_SAMPLE_INTERVAL_HIGH 200
#define HILL_CLIMBING_ERROR_SMOOTHING_FACTOR 0.01
#define HILL_CLIMBING_MAX_SAMPLE_ERROR_PERCENT 0.15
typedef enum {
TRANSITION_WARMUP,
TRANSITION_INITIALIZING,
TRANSITION_RANDOM_MOVE,
TRANSITION_CLIMBING_MOVE,
TRANSITION_CHANGE_POINT,
TRANSITION_STABILIZING,
TRANSITION_STARVATION,
TRANSITION_THREAD_TIMED_OUT,
TRANSITION_UNDEFINED,
} ThreadPoolHeuristicStateTransition;
typedef struct {
gint32 wave_period;
gint32 samples_to_measure;
gdouble target_throughput_ratio;
gdouble target_signal_to_noise_ratio;
gdouble max_change_per_second;
gdouble max_change_per_sample;
gint32 max_thread_wave_magnitude;
gint32 sample_interval_low;
gdouble thread_magnitude_multiplier;
gint32 sample_interval_high;
gdouble throughput_error_smoothing_factor;
gdouble gain_exponent;
gdouble max_sample_error;
gdouble current_control_setting;
gint64 total_samples;
gint16 last_thread_count;
gdouble elapsed_since_last_change;
gdouble completions_since_last_change;
gdouble average_throughput_noise;
gdouble *samples;
gdouble *thread_counts;
guint32 current_sample_interval;
gpointer random_interval_generator;
gint32 accumulated_completion_count;
gdouble accumulated_sample_duration;
} ThreadPoolHillClimbing;
typedef union {
struct {
gint16 max_working; /* determined by heuristic */
gint16 starting; /* starting, but not yet in worker_thread */
gint16 working; /* executing worker_thread */
gint16 parked; /* parked */
} _;
gint64 as_gint64;
} ThreadPoolWorkerCounter
#ifdef __GNUC__
__attribute__((aligned(64)))
#endif
;
typedef struct {
MonoRefCount ref;
MonoThreadPoolWorkerCallback callback;
ThreadPoolWorkerCounter counters;
MonoCoopSem parked_threads_sem;
gint32 parked_threads_count;
volatile gint32 work_items_count;
guint32 worker_creation_current_second;
guint32 worker_creation_current_count;
MonoCoopMutex worker_creation_lock;
gint32 heuristic_completions;
gint64 heuristic_sample_start;
gint64 heuristic_last_dequeue; // ms
gint64 heuristic_last_adjustment; // ms
gint64 heuristic_adjustment_interval; // ms
ThreadPoolHillClimbing heuristic_hill_climbing;
MonoCoopMutex heuristic_lock;
gint32 limit_worker_min;
gint32 limit_worker_max;
MonoCpuUsageState *cpu_usage_state;
gint32 cpu_usage;
/* suspended by the debugger */
gboolean suspended;
gint32 monitor_status;
} ThreadPoolWorker;
enum {
MONITOR_STATUS_REQUESTED,
MONITOR_STATUS_WAITING_FOR_REQUEST,
MONITOR_STATUS_NOT_RUNNING,
};
static ThreadPoolWorker worker;
#define COUNTER_CHECK(counter) \
do { \
g_assert (counter._.max_working > 0); \
g_assert (counter._.starting >= 0); \
g_assert (counter._.working >= 0); \
} while (0)
#define COUNTER_ATOMIC(var,block) \
do { \
ThreadPoolWorkerCounter __old; \
do { \
__old = COUNTER_READ (); \
(var) = __old; \
{ block; } \
COUNTER_CHECK (var); \
} while (mono_atomic_cas_i64 (&worker.counters.as_gint64, (var).as_gint64, __old.as_gint64) != __old.as_gint64); \
} while (0)
static inline ThreadPoolWorkerCounter
COUNTER_READ (void)
{
ThreadPoolWorkerCounter counter;
counter.as_gint64 = mono_atomic_load_i64 (&worker.counters.as_gint64);
return counter;
}
static gpointer
rand_create (void)
{
mono_rand_open ();
return mono_rand_init (NULL, 0);
}
static guint32
rand_next (gpointer *handle, guint32 min, guint32 max)
{
ERROR_DECL (error);
guint32 val;
mono_rand_try_get_uint32 (handle, &val, min, max, error);
// FIXME handle error
mono_error_assert_ok (error);
return val;
}
static void
destroy (gpointer data)
{
mono_coop_sem_destroy (&worker.parked_threads_sem);
mono_coop_mutex_destroy (&worker.worker_creation_lock);
mono_coop_mutex_destroy (&worker.heuristic_lock);
g_free (worker.cpu_usage_state);
}
void
mono_threadpool_worker_init (MonoThreadPoolWorkerCallback callback)
{
ThreadPoolHillClimbing *hc;
const char *threads_per_cpu_env;
gint threads_per_cpu;
gint threads_count;
mono_refcount_init (&worker, destroy);
worker.callback = callback;
mono_coop_sem_init (&worker.parked_threads_sem, 0);
worker.parked_threads_count = 0;
worker.worker_creation_current_second = -1;
mono_coop_mutex_init (&worker.worker_creation_lock);
worker.heuristic_adjustment_interval = 10;
mono_coop_mutex_init (&worker.heuristic_lock);
mono_rand_open ();
hc = &worker.heuristic_hill_climbing;
hc->wave_period = HILL_CLIMBING_WAVE_PERIOD;
hc->max_thread_wave_magnitude = HILL_CLIMBING_MAX_WAVE_MAGNITUDE;
hc->thread_magnitude_multiplier = (gdouble) HILL_CLIMBING_WAVE_MAGNITUDE_MULTIPLIER;
hc->samples_to_measure = hc->wave_period * HILL_CLIMBING_WAVE_HISTORY_SIZE;
hc->target_throughput_ratio = (gdouble) HILL_CLIMBING_BIAS;
hc->target_signal_to_noise_ratio = (gdouble) HILL_CLIMBING_TARGET_SIGNAL_TO_NOISE_RATIO;
hc->max_change_per_second = (gdouble) HILL_CLIMBING_MAX_CHANGE_PER_SECOND;
hc->max_change_per_sample = (gdouble) HILL_CLIMBING_MAX_CHANGE_PER_SAMPLE;
hc->sample_interval_low = HILL_CLIMBING_SAMPLE_INTERVAL_LOW;
hc->sample_interval_high = HILL_CLIMBING_SAMPLE_INTERVAL_HIGH;
hc->throughput_error_smoothing_factor = (gdouble) HILL_CLIMBING_ERROR_SMOOTHING_FACTOR;
hc->gain_exponent = (gdouble) HILL_CLIMBING_GAIN_EXPONENT;
hc->max_sample_error = (gdouble) HILL_CLIMBING_MAX_SAMPLE_ERROR_PERCENT;
hc->current_control_setting = 0;
hc->total_samples = 0;
hc->last_thread_count = 0;
hc->average_throughput_noise = 0;
hc->elapsed_since_last_change = 0;
hc->accumulated_completion_count = 0;
hc->accumulated_sample_duration = 0;
hc->samples = g_new0 (gdouble, hc->samples_to_measure);
hc->thread_counts = g_new0 (gdouble, hc->samples_to_measure);
hc->random_interval_generator = rand_create ();
hc->current_sample_interval = rand_next (&hc->random_interval_generator, hc->sample_interval_low, hc->sample_interval_high);
if (!(threads_per_cpu_env = g_getenv ("MONO_THREADS_PER_CPU")))
threads_per_cpu = 1;
else
threads_per_cpu = CLAMP (atoi (threads_per_cpu_env), 1, 50);
threads_count = mono_cpu_count () * threads_per_cpu;
worker.limit_worker_min = threads_count;
#if defined (HOST_ANDROID) || defined (HOST_IOS)
worker.limit_worker_max = CLAMP (threads_count * 100, MIN (threads_count, 200), MAX (threads_count, 200));
#else
worker.limit_worker_max = threads_count * 100;
#endif
worker.counters._.max_working = worker.limit_worker_min;
worker.cpu_usage_state = g_new0 (MonoCpuUsageState, 1);
worker.suspended = FALSE;
worker.monitor_status = MONITOR_STATUS_NOT_RUNNING;
}
void
mono_threadpool_worker_cleanup (void)
{
mono_refcount_dec (&worker);
}
static void
work_item_push (void)
{
gint32 old, new;
do {
old = mono_atomic_load_i32 (&worker.work_items_count);
g_assert (old >= 0);
new = old + 1;
} while (mono_atomic_cas_i32 (&worker.work_items_count, new, old) != old);
}
static gboolean
work_item_try_pop (void)
{
gint32 old, new;
do {
old = mono_atomic_load_i32 (&worker.work_items_count);
g_assert (old >= 0);
if (old == 0)
return FALSE;
new = old - 1;
} while (mono_atomic_cas_i32 (&worker.work_items_count, new, old) != old);
return TRUE;
}
static gint32
work_item_count (void)
{
return mono_atomic_load_i32 (&worker.work_items_count);
}
static void worker_request (void);
void
mono_threadpool_worker_request (void)
{
if (!mono_refcount_tryinc (&worker))
return;
work_item_push ();
worker_request ();
mono_refcount_dec (&worker);
}
/* return TRUE if timeout, FALSE otherwise (worker unpark or interrupt) */
static gboolean
worker_park (void)
{
gboolean timeout = FALSE;
gboolean interrupted = FALSE;
gint32 old, new;
mono_trace (G_LOG_LEVEL_DEBUG, MONO_TRACE_THREADPOOL, "[%p] worker parking",
GUINT_TO_POINTER (MONO_NATIVE_THREAD_ID_TO_UINT (mono_native_thread_id_get ())));
if (!mono_runtime_is_shutting_down ()) {
static gpointer rand_handle = NULL;
ThreadPoolWorkerCounter counter;
if (!rand_handle) {
rand_handle = rand_create ();
g_assert (rand_handle);
}
COUNTER_ATOMIC (counter, {
counter._.working --;
counter._.parked ++;
});
do {
old = mono_atomic_load_i32 (&worker.parked_threads_count);
g_assert (old >= G_MININT32);
new = old + 1;
} while (mono_atomic_cas_i32 (&worker.parked_threads_count, new, old) != old);
switch (mono_coop_sem_timedwait (&worker.parked_threads_sem, rand_next (&rand_handle, 5 * 1000, 60 * 1000), MONO_SEM_FLAGS_ALERTABLE)) {
case MONO_SEM_TIMEDWAIT_RET_SUCCESS:
break;
case MONO_SEM_TIMEDWAIT_RET_ALERTED:
interrupted = TRUE;
break;
case MONO_SEM_TIMEDWAIT_RET_TIMEDOUT:
timeout = TRUE;
break;
default:
g_assert_not_reached ();
}
if (interrupted || timeout) {
/* If the semaphore was posted, then worker.parked_threads_count was decremented in worker_try_unpark */
do {
old = mono_atomic_load_i32 (&worker.parked_threads_count);
g_assert (old > G_MININT32);
new = old - 1;
} while (mono_atomic_cas_i32 (&worker.parked_threads_count, new, old) != old);
}
COUNTER_ATOMIC (counter, {
counter._.working ++;
counter._.parked --;
});
}
mono_trace (G_LOG_LEVEL_DEBUG, MONO_TRACE_THREADPOOL, "[%p] worker unparking, timeout? %s interrupted? %s",
GUINT_TO_POINTER (MONO_NATIVE_THREAD_ID_TO_UINT (mono_native_thread_id_get ())), timeout ? "yes" : "no", interrupted ? "yes" : "no");
return timeout;
}
static gboolean
worker_try_unpark (void)
{
gboolean res = TRUE;
gint32 old, new;
mono_trace (G_LOG_LEVEL_DEBUG, MONO_TRACE_THREADPOOL, "[%p] try unpark worker",
GUINT_TO_POINTER (MONO_NATIVE_THREAD_ID_TO_UINT (mono_native_thread_id_get ())));
do {
old = mono_atomic_load_i32 (&worker.parked_threads_count);
g_assert (old > G_MININT32);
if (old <= 0) {
res = FALSE;
break;
}
new = old - 1;
} while (mono_atomic_cas_i32 (&worker.parked_threads_count, new, old) != old);
if (res)
mono_coop_sem_post (&worker.parked_threads_sem);
mono_trace (G_LOG_LEVEL_DEBUG, MONO_TRACE_THREADPOOL, "[%p] try unpark worker, success? %s",
GUINT_TO_POINTER (MONO_NATIVE_THREAD_ID_TO_UINT (mono_native_thread_id_get ())), res ? "yes" : "no");
return res;
}
static gsize WINAPI
worker_thread (gpointer unused)
{
MonoInternalThread *thread;
ThreadPoolWorkerCounter counter;
mono_trace (G_LOG_LEVEL_DEBUG, MONO_TRACE_THREADPOOL, "[%p] worker starting",
GUINT_TO_POINTER (MONO_NATIVE_THREAD_ID_TO_UINT (mono_native_thread_id_get ())));
if (!mono_refcount_tryinc (&worker))
return 0;
COUNTER_ATOMIC (counter, {
counter._.starting --;
counter._.working ++;
});
thread = mono_thread_internal_current ();
g_assert (thread);
while (!mono_runtime_is_shutting_down ()) {
if (mono_thread_interruption_checkpoint_bool ())
continue;
// If a worker thread is in its native top, not running managed code,
// there is no point in raising thread abort, and no code will clear
// the abort request. As such, the subsequent timedwait, would
// not be interrupted at runtime shutdown, because an abort is already requested.
// Clear the abort request.
// This avoids a shutdown hang in tests thread6 and thread7.
if (thread->state & ThreadState_AbortRequested)
mono_thread_internal_reset_abort (thread);
if (!work_item_try_pop ()) {
gboolean const timeout = worker_park ();
if (timeout)
break;
continue;
}
mono_trace (G_LOG_LEVEL_DEBUG, MONO_TRACE_THREADPOOL, "[%p] worker executing",
GUINT_TO_POINTER (MONO_NATIVE_THREAD_ID_TO_UINT (mono_native_thread_id_get ())));
worker.callback ();
}
COUNTER_ATOMIC (counter, {
counter._.working --;
});
mono_trace (G_LOG_LEVEL_DEBUG, MONO_TRACE_THREADPOOL, "[%p] worker finishing",
GUINT_TO_POINTER (MONO_NATIVE_THREAD_ID_TO_UINT (mono_native_thread_id_get ())));
mono_refcount_dec (&worker);
return 0;
}
static gboolean
worker_try_create (void)
{
ERROR_DECL (error);
MonoInternalThread *thread;
gint64 current_ticks;
gint32 now;
ThreadPoolWorkerCounter counter;
if (mono_runtime_is_shutting_down ())
return FALSE;
mono_coop_mutex_lock (&worker.worker_creation_lock);
mono_trace (G_LOG_LEVEL_DEBUG, MONO_TRACE_THREADPOOL, "[%p] try create worker",
GUINT_TO_POINTER (MONO_NATIVE_THREAD_ID_TO_UINT (mono_native_thread_id_get ())));
current_ticks = mono_100ns_ticks ();
if (0 == current_ticks) {
g_warning ("failed to get 100ns ticks");
} else {
now = current_ticks / (10 * 1000 * 1000);
if (worker.worker_creation_current_second != now) {
worker.worker_creation_current_second = now;
worker.worker_creation_current_count = 0;
} else {
g_assert (worker.worker_creation_current_count <= WORKER_CREATION_MAX_PER_SEC);
if (worker.worker_creation_current_count == WORKER_CREATION_MAX_PER_SEC) {
mono_trace (G_LOG_LEVEL_DEBUG, MONO_TRACE_THREADPOOL, "[%p] try create worker, failed: maximum number of worker created per second reached, current count = %d",
GUINT_TO_POINTER (MONO_NATIVE_THREAD_ID_TO_UINT (mono_native_thread_id_get ())), worker.worker_creation_current_count);
mono_coop_mutex_unlock (&worker.worker_creation_lock);
return FALSE;
}
}
}
COUNTER_ATOMIC (counter, {
if (counter._.working >= counter._.max_working) {
mono_trace (G_LOG_LEVEL_DEBUG, MONO_TRACE_THREADPOOL, "[%p] try create worker, failed: maximum number of working threads reached",
GUINT_TO_POINTER (MONO_NATIVE_THREAD_ID_TO_UINT (mono_native_thread_id_get ())));
mono_coop_mutex_unlock (&worker.worker_creation_lock);
return FALSE;
}
counter._.starting ++;
});
thread = mono_thread_create_internal (mono_get_root_domain (), worker_thread, NULL, MONO_THREAD_CREATE_FLAGS_THREADPOOL, error);
if (!thread) {
mono_trace (G_LOG_LEVEL_DEBUG, MONO_TRACE_THREADPOOL, "[%p] try create worker, failed: could not create thread due to %s",
GUINT_TO_POINTER (MONO_NATIVE_THREAD_ID_TO_UINT (mono_native_thread_id_get ())), mono_error_get_message (error));
mono_error_cleanup (error);
COUNTER_ATOMIC (counter, {
counter._.starting --;
});
mono_coop_mutex_unlock (&worker.worker_creation_lock);
return FALSE;
}
#ifndef DISABLE_PERFCOUNTERS
mono_atomic_inc_i32 (&mono_perfcounters->threadpool_threads);
#endif
worker.worker_creation_current_count += 1;
mono_trace (G_LOG_LEVEL_DEBUG, MONO_TRACE_THREADPOOL, "[%p] try create worker, created %p, now = %d count = %d",
GUINT_TO_POINTER (MONO_NATIVE_THREAD_ID_TO_UINT (mono_native_thread_id_get ())), (gpointer) thread->tid, now, worker.worker_creation_current_count);
mono_coop_mutex_unlock (&worker.worker_creation_lock);
return TRUE;
}
static void monitor_ensure_running (void);
static void
worker_request (void)
{
if (worker.suspended)
return;
monitor_ensure_running ();
if (worker_try_unpark ()) {
mono_trace (G_LOG_LEVEL_DEBUG, MONO_TRACE_THREADPOOL, "[%p] request worker, unparked",
GUINT_TO_POINTER (MONO_NATIVE_THREAD_ID_TO_UINT (mono_native_thread_id_get ())));
return;
}
if (worker_try_create ()) {
mono_trace (G_LOG_LEVEL_DEBUG, MONO_TRACE_THREADPOOL, "[%p] request worker, created",
GUINT_TO_POINTER (MONO_NATIVE_THREAD_ID_TO_UINT (mono_native_thread_id_get ())));
return;
}
mono_trace (G_LOG_LEVEL_DEBUG, MONO_TRACE_THREADPOOL, "[%p] request worker, failed",
GUINT_TO_POINTER (MONO_NATIVE_THREAD_ID_TO_UINT (mono_native_thread_id_get ())));
}
static gboolean
monitor_should_keep_running (void)
{
static gint64 last_should_keep_running = -1;
g_assert (worker.monitor_status == MONITOR_STATUS_WAITING_FOR_REQUEST || worker.monitor_status == MONITOR_STATUS_REQUESTED);
if (mono_atomic_xchg_i32 (&worker.monitor_status, MONITOR_STATUS_WAITING_FOR_REQUEST) == MONITOR_STATUS_WAITING_FOR_REQUEST) {
gboolean should_keep_running = TRUE, force_should_keep_running = FALSE;
if (mono_runtime_is_shutting_down ()) {
should_keep_running = FALSE;
} else {
if (work_item_count () == 0)
should_keep_running = FALSE;
if (!should_keep_running) {
if (last_should_keep_running == -1 || mono_100ns_ticks () - last_should_keep_running < MONITOR_MINIMAL_LIFETIME * 1000 * 10) {
should_keep_running = force_should_keep_running = TRUE;
}
}
}
if (should_keep_running) {
if (last_should_keep_running == -1 || !force_should_keep_running)
last_should_keep_running = mono_100ns_ticks ();
} else {
last_should_keep_running = -1;
if (mono_atomic_cas_i32 (&worker.monitor_status, MONITOR_STATUS_NOT_RUNNING, MONITOR_STATUS_WAITING_FOR_REQUEST) == MONITOR_STATUS_WAITING_FOR_REQUEST)
return FALSE;
}
}
g_assert (worker.monitor_status == MONITOR_STATUS_WAITING_FOR_REQUEST || worker.monitor_status == MONITOR_STATUS_REQUESTED);
return TRUE;
}
static gboolean
monitor_sufficient_delay_since_last_dequeue (void)
{
gint64 threshold;
if (worker.cpu_usage < CPU_USAGE_LOW) {
threshold = MONITOR_INTERVAL;
} else {
threshold = COUNTER_READ ()._.max_working * MONITOR_INTERVAL * 2;
}
return mono_msec_ticks () >= worker.heuristic_last_dequeue + threshold;
}
static void hill_climbing_force_change (gint16 new_thread_count, ThreadPoolHeuristicStateTransition transition);
static gsize WINAPI
monitor_thread (gpointer unused)
{
MonoInternalThread *internal;
guint i;
if (!mono_refcount_tryinc (&worker))
return 0;
internal = mono_thread_internal_current ();
g_assert (internal);
mono_cpu_usage (worker.cpu_usage_state);
// printf ("monitor_thread: start\n");
mono_trace (G_LOG_LEVEL_DEBUG, MONO_TRACE_THREADPOOL, "[%p] monitor thread, started",
GUINT_TO_POINTER (MONO_NATIVE_THREAD_ID_TO_UINT (mono_native_thread_id_get ())));
do {
ThreadPoolWorkerCounter counter;
gboolean limit_worker_max_reached;
gint32 interval_left = MONITOR_INTERVAL;
gint32 awake = 0; /* number of spurious awakes we tolerate before doing a round of rebalancing */
g_assert (worker.monitor_status != MONITOR_STATUS_NOT_RUNNING);
// counter = COUNTER_READ ();
// printf ("monitor_thread: starting = %d working = %d parked = %d max_working = %d\n",
// counter._.starting, counter._.working, counter._.parked, counter._.max_working);
do {
gint64 ts;
gboolean alerted = FALSE;
if (mono_runtime_is_shutting_down ())
break;
ts = mono_msec_ticks ();
if (mono_thread_info_sleep (interval_left, &alerted) == 0)
break;
interval_left -= mono_msec_ticks () - ts;
mono_thread_interruption_checkpoint_void ();
} while (interval_left > 0 && ++awake < 10);
if (mono_runtime_is_shutting_down ())
continue;
if (worker.suspended)
continue;
if (work_item_count () == 0)
continue;
worker.cpu_usage = mono_cpu_usage (worker.cpu_usage_state);
if (!monitor_sufficient_delay_since_last_dequeue ())
continue;
limit_worker_max_reached = FALSE;
COUNTER_ATOMIC (counter, {
if (counter._.max_working >= worker.limit_worker_max) {
limit_worker_max_reached = TRUE;
break;
}
counter._.max_working ++;
});
if (limit_worker_max_reached)
continue;
hill_climbing_force_change (counter._.max_working, TRANSITION_STARVATION);
for (i = 0; i < 5; ++i) {
if (mono_runtime_is_shutting_down ())
break;
if (worker_try_unpark ()) {
mono_trace (G_LOG_LEVEL_DEBUG, MONO_TRACE_THREADPOOL, "[%p] monitor thread, unparked",
GUINT_TO_POINTER (MONO_NATIVE_THREAD_ID_TO_UINT (mono_native_thread_id_get ())));
break;
}
if (worker_try_create ()) {
mono_trace (G_LOG_LEVEL_DEBUG, MONO_TRACE_THREADPOOL, "[%p] monitor thread, created",
GUINT_TO_POINTER (MONO_NATIVE_THREAD_ID_TO_UINT (mono_native_thread_id_get ())));
break;
}
}
} while (monitor_should_keep_running ());
// printf ("monitor_thread: stop\n");
mono_trace (G_LOG_LEVEL_DEBUG, MONO_TRACE_THREADPOOL, "[%p] monitor thread, finished",
GUINT_TO_POINTER (MONO_NATIVE_THREAD_ID_TO_UINT (mono_native_thread_id_get ())));
mono_refcount_dec (&worker);
return 0;
}
static void
monitor_ensure_running (void)
{
ERROR_DECL (error);
for (;;) {
switch (worker.monitor_status) {
case MONITOR_STATUS_REQUESTED:
// printf ("monitor_thread: requested\n");
return;
case MONITOR_STATUS_WAITING_FOR_REQUEST:
// printf ("monitor_thread: waiting for request\n");
mono_atomic_cas_i32 (&worker.monitor_status, MONITOR_STATUS_REQUESTED, MONITOR_STATUS_WAITING_FOR_REQUEST);
break;
case MONITOR_STATUS_NOT_RUNNING:
// printf ("monitor_thread: not running\n");
if (mono_runtime_is_shutting_down ())
return;
if (mono_atomic_cas_i32 (&worker.monitor_status, MONITOR_STATUS_REQUESTED, MONITOR_STATUS_NOT_RUNNING) == MONITOR_STATUS_NOT_RUNNING) {
// printf ("monitor_thread: creating\n");
if (!mono_thread_create_internal (mono_get_root_domain (), monitor_thread, NULL, MONO_THREAD_CREATE_FLAGS_THREADPOOL | MONO_THREAD_CREATE_FLAGS_SMALL_STACK, error)) {
// printf ("monitor_thread: creating failed\n");
worker.monitor_status = MONITOR_STATUS_NOT_RUNNING;
mono_error_cleanup (error);
mono_refcount_dec (&worker);
}
return;
}
break;
default: g_assert_not_reached ();
}
}
}
static void
hill_climbing_change_thread_count (gint16 new_thread_count, ThreadPoolHeuristicStateTransition transition)
{
ThreadPoolHillClimbing *hc;
hc = &worker.heuristic_hill_climbing;
mono_trace (G_LOG_LEVEL_DEBUG, MONO_TRACE_THREADPOOL, "[%p] hill climbing, change max number of threads %d",
GUINT_TO_POINTER (MONO_NATIVE_THREAD_ID_TO_UINT (mono_native_thread_id_get ())), new_thread_count);
hc->last_thread_count = new_thread_count;
hc->current_sample_interval = rand_next (&hc->random_interval_generator, hc->sample_interval_low, hc->sample_interval_high);
hc->elapsed_since_last_change = 0;
hc->completions_since_last_change = 0;
}
static void
hill_climbing_force_change (gint16 new_thread_count, ThreadPoolHeuristicStateTransition transition)
{
ThreadPoolHillClimbing *hc;
hc = &worker.heuristic_hill_climbing;
if (new_thread_count != hc->last_thread_count) {
hc->current_control_setting += new_thread_count - hc->last_thread_count;
hill_climbing_change_thread_count (new_thread_count, transition);
}
}
static double_complex
hill_climbing_get_wave_component (gdouble *samples, guint sample_count, gdouble period)
{
ThreadPoolHillClimbing *hc;
gdouble w, cosine, sine, coeff, q0, q1, q2;
guint i;
g_assert (sample_count >= period);
g_assert (period >= 2);
hc = &worker.heuristic_hill_climbing;
w = 2.0 * M_PI / period;
cosine = cos (w);
sine = sin (w);
coeff = 2.0 * cosine;
q0 = q1 = q2 = 0;
for (i = 0; i < sample_count; ++i) {
q0 = coeff * q1 - q2 + samples [(hc->total_samples - sample_count + i) % hc->samples_to_measure];
q2 = q1;
q1 = q0;
}
return mono_double_complex_scalar_div (mono_double_complex_make (q1 - q2 * cosine, (q2 * sine)), ((gdouble)sample_count));
}
static gint16
hill_climbing_update (gint16 current_thread_count, guint32 sample_duration, gint32 completions, gint64 *adjustment_interval)
{
ThreadPoolHillClimbing *hc;
ThreadPoolHeuristicStateTransition transition;
gdouble throughput;
gdouble throughput_error_estimate;
gdouble confidence;
gdouble move;
gdouble gain;
gint sample_index;
gint sample_count;
gint new_thread_wave_magnitude;
gint new_thread_count;
double_complex thread_wave_component;
double_complex throughput_wave_component;
double_complex ratio;
g_assert (adjustment_interval);
hc = &worker.heuristic_hill_climbing;
/* If someone changed the thread count without telling us, update our records accordingly. */
if (current_thread_count != hc->last_thread_count)
hill_climbing_force_change (current_thread_count, TRANSITION_INITIALIZING);
/* Update the cumulative stats for this thread count */
hc->elapsed_since_last_change += sample_duration;
hc->completions_since_last_change += completions;
/* Add in any data we've already collected about this sample */
sample_duration += hc->accumulated_sample_duration;
completions += hc->accumulated_completion_count;
/* We need to make sure we're collecting reasonably accurate data. Since we're just counting the end
* of each work item, we are goinng to be missing some data about what really happened during the
* sample interval. The count produced by each thread includes an initial work item that may have
* started well before the start of the interval, and each thread may have been running some new
* work item for some time before the end of the interval, which did not yet get counted. So
* our count is going to be off by +/- threadCount workitems.
*
* The exception is that the thread that reported to us last time definitely wasn't running any work
* at that time, and the thread that's reporting now definitely isn't running a work item now. So
* we really only need to consider threadCount-1 threads.
*
* Thus the percent error in our count is +/- (threadCount-1)/numCompletions.
*
* We cannot rely on the frequency-domain analysis we'll be doing later to filter out this error, because
* of the way it accumulates over time. If this sample is off by, say, 33% in the negative direction,
* then the next one likely will be too. The one after that will include the sum of the completions
* we missed in the previous samples, and so will be 33% positive. So every three samples we'll have
* two "low" samples and one "high" sample. This will appear as periodic variation right in the frequency
* range we're targeting, which will not be filtered by the frequency-domain translation. */
if (hc->total_samples > 0 && ((current_thread_count - 1.0) / completions) >= hc->max_sample_error) {
/* Not accurate enough yet. Let's accumulate the data so
* far, and tell the ThreadPoolWorker to collect a little more. */
hc->accumulated_sample_duration = sample_duration;
hc->accumulated_completion_count = completions;
*adjustment_interval = 10;
return current_thread_count;
}
/* We've got enouugh data for our sample; reset our accumulators for next time. */
hc->accumulated_sample_duration = 0;
hc->accumulated_completion_count = 0;
/* Add the current thread count and throughput sample to our history. */
throughput = ((gdouble) completions) / sample_duration;
sample_index = hc->total_samples % hc->samples_to_measure;
hc->samples [sample_index] = throughput;
hc->thread_counts [sample_index] = current_thread_count;
hc->total_samples ++;
/* Set up defaults for our metrics. */
thread_wave_component = mono_double_complex_make(0, 0);
throughput_wave_component = mono_double_complex_make(0, 0);
throughput_error_estimate = 0;
ratio = mono_double_complex_make(0, 0);
confidence = 0;
transition = TRANSITION_WARMUP;
/* How many samples will we use? It must be at least the three wave periods we're looking for, and it must also
* be a whole multiple of the primary wave's period; otherwise the frequency we're looking for will fall between
* two frequency bands in the Fourier analysis, and we won't be able to measure it accurately. */
sample_count = ((gint) MIN (hc->total_samples - 1, hc->samples_to_measure) / hc->wave_period) * hc->wave_period;
if (sample_count > hc->wave_period) {
guint i;
gdouble average_throughput;
gdouble average_thread_count;
gdouble sample_sum = 0;
gdouble thread_sum = 0;
/* Average the throughput and thread count samples, so we can scale the wave magnitudes later. */
for (i = 0; i < sample_count; ++i) {
guint j = (hc->total_samples - sample_count + i) % hc->samples_to_measure;
sample_sum += hc->samples [j];
thread_sum += hc->thread_counts [j];
}
average_throughput = sample_sum / sample_count;
average_thread_count = thread_sum / sample_count;
if (average_throughput > 0 && average_thread_count > 0) {
gdouble noise_for_confidence, adjacent_period_1, adjacent_period_2;
/* Calculate the periods of the adjacent frequency bands we'll be using to
* measure noise levels. We want the two adjacent Fourier frequency bands. */
adjacent_period_1 = sample_count / (((gdouble) sample_count) / ((gdouble) hc->wave_period) + 1);
adjacent_period_2 = sample_count / (((gdouble) sample_count) / ((gdouble) hc->wave_period) - 1);
/* Get the the three different frequency components of the throughput (scaled by average
* throughput). Our "error" estimate (the amount of noise that might be present in the
* frequency band we're really interested in) is the average of the adjacent bands. */
throughput_wave_component = mono_double_complex_scalar_div (hill_climbing_get_wave_component (hc->samples, sample_count, hc->wave_period), average_throughput);
throughput_error_estimate = cabs (mono_double_complex_scalar_div (hill_climbing_get_wave_component (hc->samples, sample_count, adjacent_period_1), average_throughput));
if (adjacent_period_2 <= sample_count) {
throughput_error_estimate = MAX (throughput_error_estimate, cabs (mono_double_complex_scalar_div (hill_climbing_get_wave_component (
hc->samples, sample_count, adjacent_period_2), average_throughput)));
}
/* Do the same for the thread counts, so we have something to compare to. We don't
* measure thread count noise, because there is none; these are exact measurements. */
thread_wave_component = mono_double_complex_scalar_div (hill_climbing_get_wave_component (hc->thread_counts, sample_count, hc->wave_period), average_thread_count);
/* Update our moving average of the throughput noise. We'll use this
* later as feedback to determine the new size of the thread wave. */
if (hc->average_throughput_noise == 0) {
hc->average_throughput_noise = throughput_error_estimate;
} else {
hc->average_throughput_noise = (hc->throughput_error_smoothing_factor * throughput_error_estimate)
+ ((1.0 + hc->throughput_error_smoothing_factor) * hc->average_throughput_noise);
}
if (cabs (thread_wave_component) > 0) {
/* Adjust the throughput wave so it's centered around the target wave,
* and then calculate the adjusted throughput/thread ratio. */
ratio = mono_double_complex_div (mono_double_complex_sub (throughput_wave_component, mono_double_complex_scalar_mul(thread_wave_component, hc->target_throughput_ratio)), thread_wave_component);
transition = TRANSITION_CLIMBING_MOVE;
} else {
ratio = mono_double_complex_make (0, 0);
transition = TRANSITION_STABILIZING;
}
noise_for_confidence = MAX (hc->average_throughput_noise, throughput_error_estimate);
if (noise_for_confidence > 0) {
confidence = cabs (thread_wave_component) / noise_for_confidence / hc->target_signal_to_noise_ratio;
} else {
/* there is no noise! */
confidence = 1.0;
}
}
}
/* We use just the real part of the complex ratio we just calculated. If the throughput signal
* is exactly in phase with the thread signal, this will be the same as taking the magnitude of
* the complex move and moving that far up. If they're 180 degrees out of phase, we'll move
* backward (because this indicates that our changes are having the opposite of the intended effect).
* If they're 90 degrees out of phase, we won't move at all, because we can't tell wether we're
* having a negative or positive effect on throughput. */
move = creal (ratio);
move = CLAMP (move, -1.0, 1.0);
/* Apply our confidence multiplier. */
move *= CLAMP (confidence, -1.0, 1.0);
/* Now apply non-linear gain, such that values around zero are attenuated, while higher values
* are enhanced. This allows us to move quickly if we're far away from the target, but more slowly
* if we're getting close, giving us rapid ramp-up without wild oscillations around the target. */
gain = hc->max_change_per_second * sample_duration;
move = pow (fabs (move), hc->gain_exponent) * (move >= 0.0 ? 1 : -1) * gain;
move = MIN (move, hc->max_change_per_sample);
/* If the result was positive, and CPU is > 95%, refuse the move. */
if (move > 0.0 && worker.cpu_usage > CPU_USAGE_HIGH)
move = 0.0;
/* Apply the move to our control setting. */
hc->current_control_setting += move;
/* Calculate the new thread wave magnitude, which is based on the moving average we've been keeping of the
* throughput error. This average starts at zero, so we'll start with a nice safe little wave at first. */
new_thread_wave_magnitude = (gint)(0.5 + (hc->current_control_setting * hc->average_throughput_noise
* hc->target_signal_to_noise_ratio * hc->thread_magnitude_multiplier * 2.0));
new_thread_wave_magnitude = CLAMP (new_thread_wave_magnitude, 1, hc->max_thread_wave_magnitude);
/* Make sure our control setting is within the ThreadPoolWorker's limits. */
hc->current_control_setting = CLAMP (hc->current_control_setting, worker.limit_worker_min, worker.limit_worker_max - new_thread_wave_magnitude);
/* Calculate the new thread count (control setting + square wave). */
new_thread_count = (gint)(hc->current_control_setting + new_thread_wave_magnitude * ((hc->total_samples / (hc->wave_period / 2)) % 2));
/* Make sure the new thread count doesn't exceed the ThreadPoolWorker's limits. */
new_thread_count = CLAMP (new_thread_count, worker.limit_worker_min, worker.limit_worker_max);
if (new_thread_count != current_thread_count)
hill_climbing_change_thread_count (new_thread_count, transition);
if (creal (ratio) < 0.0 && new_thread_count == worker.limit_worker_min)
*adjustment_interval = (gint)(0.5 + hc->current_sample_interval * (10.0 * MAX (-1.0 * creal (ratio), 1.0)));
else
*adjustment_interval = hc->current_sample_interval;
return new_thread_count;
}
static gboolean
heuristic_should_adjust (void)
{
if (worker.heuristic_last_dequeue > worker.heuristic_last_adjustment + worker.heuristic_adjustment_interval) {
ThreadPoolWorkerCounter const counter = COUNTER_READ ();
if (counter._.working <= counter._.max_working)
return TRUE;
}
return FALSE;
}
static void
heuristic_adjust (void)
{
if (mono_coop_mutex_trylock (&worker.heuristic_lock) == 0) {
gint32 completions = mono_atomic_xchg_i32 (&worker.heuristic_completions, 0);
gint64 sample_end = mono_msec_ticks ();
gint64 sample_duration = sample_end - worker.heuristic_sample_start;
if (sample_duration >= worker.heuristic_adjustment_interval / 2) {
ThreadPoolWorkerCounter counter = COUNTER_READ ();
gint16 const new_thread_count = hill_climbing_update (counter._.max_working, sample_duration, completions, &worker.heuristic_adjustment_interval);
COUNTER_ATOMIC (counter, {
counter._.max_working = new_thread_count;
});
if (new_thread_count > counter._.max_working)
worker_request ();
worker.heuristic_sample_start = sample_end;
worker.heuristic_last_adjustment = mono_msec_ticks ();
}
mono_coop_mutex_unlock (&worker.heuristic_lock);
}
}
static void
heuristic_notify_work_completed (void)
{
mono_atomic_inc_i32 (&worker.heuristic_completions);
worker.heuristic_last_dequeue = mono_msec_ticks ();
if (heuristic_should_adjust ())
heuristic_adjust ();
}
gboolean
mono_threadpool_worker_notify_completed (void)
{
heuristic_notify_work_completed ();
ThreadPoolWorkerCounter const counter = COUNTER_READ ();
return counter._.working <= counter._.max_working;
}
gint32
mono_threadpool_worker_get_min (void)
{
gint32 ret;
if (!mono_refcount_tryinc (&worker))
return 0;
ret = worker.limit_worker_min;
mono_refcount_dec (&worker);
return ret;
}
gboolean
mono_threadpool_worker_set_min (gint32 value)
{
if (value <= 0 || value > worker.limit_worker_max)
return FALSE;
if (!mono_refcount_tryinc (&worker))
return FALSE;
worker.limit_worker_min = value;
mono_refcount_dec (&worker);
return TRUE;
}
gint32
mono_threadpool_worker_get_max (void)
{
gint32 ret;
if (!mono_refcount_tryinc (&worker))
return 0;
ret = worker.limit_worker_max;
mono_refcount_dec (&worker);
return ret;
}
gboolean
mono_threadpool_worker_set_max (gint32 value)
{
gint32 cpu_count;
cpu_count = mono_cpu_count ();
if (value < worker.limit_worker_min || value < cpu_count)
return FALSE;
if (!mono_refcount_tryinc (&worker))
return FALSE;
worker.limit_worker_max = value;
mono_refcount_dec (&worker);
return TRUE;
}
void
mono_threadpool_worker_set_suspended (gboolean suspended)
{
if (!mono_refcount_tryinc (&worker))
return;
worker.suspended = suspended;
if (!suspended)
worker_request ();
mono_refcount_dec (&worker);
}