mono/metadata/threadpool-worker-default.c

   1 /*
   2  * threadpool-worker.c: native threadpool worker
   3  *
   4  * Author:
   5  *      Ludovic Henry (ludovic.henry@xamarin.com)
   6  *
   7  * Licensed under the MIT license. See LICENSE file in the project root for full license information.
   8  */
   9
  10 #include <stdlib.h>
  11 #define _USE_MATH_DEFINES // needed by MSVC to define math constants
  12 #include <math.h>
  13 #include <config.h>
  14 #include <glib.h>
  15
  16 #include <mono/metadata/class-internals.h>
  17 #include <mono/metadata/exception.h>
  18 #include <mono/metadata/gc-internals.h>
  19 #include <mono/metadata/object.h>
  20 #include <mono/metadata/object-internals.h>
  21 #include <mono/metadata/threadpool.h>
  22 #include <mono/metadata/threadpool-worker.h>
  23 #include <mono/metadata/threadpool-io.h>
  24 #include <mono/metadata/w32event.h>
  25 #include <mono/utils/atomic.h>
  26 #include <mono/utils/mono-compiler.h>
  27 #include <mono/utils/mono-complex.h>
  28 #include <mono/utils/mono-logger.h>
  29 #include <mono/utils/mono-logger-internals.h>
  30 #include <mono/utils/mono-proclib.h>
  31 #include <mono/utils/mono-threads.h>
  32 #include <mono/utils/mono-time.h>
  33 #include <mono/utils/mono-rand.h>
  34 #include <mono/utils/refcount.h>
  35 #include <mono/utils/w32api.h>
  36
  37 #define CPU_USAGE_LOW 80
  38 #define CPU_USAGE_HIGH 95
  39
  40 #define MONITOR_INTERVAL 500 // ms
  41 #define MONITOR_MINIMAL_LIFETIME 60 * 1000 // ms
  42
  43 #define WORKER_CREATION_MAX_PER_SEC 10
  44
  45 /* The exponent to apply to the gain. 1.0 means to use linear gain,
  46  * higher values will enhance large moves and damp small ones.
  47  * default: 2.0 */
  48 #define HILL_CLIMBING_GAIN_EXPONENT 2.0
  49
  50 /* The 'cost' of a thread. 0 means drive for increased throughput regardless
  51  * of thread count, higher values bias more against higher thread counts.
  52  * default: 0.15 */
  53 #define HILL_CLIMBING_BIAS 0.15
  54
  55 #define HILL_CLIMBING_WAVE_PERIOD 4
  56 #define HILL_CLIMBING_MAX_WAVE_MAGNITUDE 20
  57 #define HILL_CLIMBING_WAVE_MAGNITUDE_MULTIPLIER 1.0
  58 #define HILL_CLIMBING_WAVE_HISTORY_SIZE 8
  59 #define HILL_CLIMBING_TARGET_SIGNAL_TO_NOISE_RATIO 3.0
  60 #define HILL_CLIMBING_MAX_CHANGE_PER_SECOND 4
  61 #define HILL_CLIMBING_MAX_CHANGE_PER_SAMPLE 20
  62 #define HILL_CLIMBING_SAMPLE_INTERVAL_LOW 10
  63 #define HILL_CLIMBING_SAMPLE_INTERVAL_HIGH 200
  64 #define HILL_CLIMBING_ERROR_SMOOTHING_FACTOR 0.01
  65 #define HILL_CLIMBING_MAX_SAMPLE_ERROR_PERCENT 0.15
  66
  67 typedef enum {
  68         TRANSITION_WARMUP,
  69         TRANSITION_INITIALIZING,
  70         TRANSITION_RANDOM_MOVE,
  71         TRANSITION_CLIMBING_MOVE,
  72         TRANSITION_CHANGE_POINT,
  73         TRANSITION_STABILIZING,
  74         TRANSITION_STARVATION,
  75         TRANSITION_THREAD_TIMED_OUT,
  76         TRANSITION_UNDEFINED,
  77 } ThreadPoolHeuristicStateTransition;
  78
  79 typedef struct {
  80         gint32 wave_period;
  81         gint32 samples_to_measure;
  82         gdouble target_throughput_ratio;
  83         gdouble target_signal_to_noise_ratio;
  84         gdouble max_change_per_second;
  85         gdouble max_change_per_sample;
  86         gint32 max_thread_wave_magnitude;
  87         gint32 sample_interval_low;
  88         gdouble thread_magnitude_multiplier;
  89         gint32 sample_interval_high;
  90         gdouble throughput_error_smoothing_factor;
  91         gdouble gain_exponent;
  92         gdouble max_sample_error;
  93
  94         gdouble current_control_setting;
  95         gint64 total_samples;
  96         gint16 last_thread_count;
  97         gdouble elapsed_since_last_change;
  98         gdouble completions_since_last_change;
  99
 100         gdouble average_throughput_noise;
 101
 102         gdouble *samples;
 103         gdouble *thread_counts;
 104
 105         guint32 current_sample_interval;
 106         gpointer random_interval_generator;
 107
 108         gint32 accumulated_completion_count;
 109         gdouble accumulated_sample_duration;
 110 } ThreadPoolHillClimbing;
 111
 112 typedef struct {
 113         MonoThreadPoolWorkerCallback callback;
 114         gpointer data;
 115 } ThreadPoolWorkItem;
 116
 117 typedef union {
 118         struct {
 119                 gint16 max_working; /* determined by heuristic */
 120                 gint16 starting; /* starting, but not yet in worker_thread */
 121                 gint16 working; /* executing worker_thread */
 122                 gint16 parked; /* parked */
 123         } _;
 124         gint64 as_gint64;
 125 } ThreadPoolWorkerCounter;
 126
 127 typedef MonoInternalThread ThreadPoolWorkerThread;
 128
 129 typedef struct {
 130         MonoRefCount ref;
 131
 132         ThreadPoolWorkerCounter counters;
 133
 134         GPtrArray *threads; // ThreadPoolWorkerThread* []
 135         MonoCoopMutex threads_lock; /* protect access to working_threads and parked_threads */
 136         gint32 parked_threads_count;
 137         MonoCoopCond parked_threads_cond;
 138         MonoCoopCond threads_exit_cond;
 139
 140         ThreadPoolWorkItem *work_items; // ThreadPoolWorkItem []
 141         gint32 work_items_count;
 142         gint32 work_items_size;
 143         MonoCoopMutex work_items_lock;
 144
 145         guint32 worker_creation_current_second;
 146         guint32 worker_creation_current_count;
 147         MonoCoopMutex worker_creation_lock;
 148
 149         gint32 heuristic_completions;
 150         gint64 heuristic_sample_start;
 151         gint64 heuristic_last_dequeue; // ms
 152         gint64 heuristic_last_adjustment; // ms
 153         gint64 heuristic_adjustment_interval; // ms
 154         ThreadPoolHillClimbing heuristic_hill_climbing;
 155         MonoCoopMutex heuristic_lock;
 156
 157         gint32 limit_worker_min;
 158         gint32 limit_worker_max;
 159
 160         MonoCpuUsageState *cpu_usage_state;
 161         gint32 cpu_usage;
 162
 163         /* suspended by the debugger */
 164         gboolean suspended;
 165
 166         gint32 monitor_status;
 167 } ThreadPoolWorker;
 168
 169 enum {
 170         MONITOR_STATUS_REQUESTED,
 171         MONITOR_STATUS_WAITING_FOR_REQUEST,
 172         MONITOR_STATUS_NOT_RUNNING,
 173 };
 174
 175 static ThreadPoolWorker worker;
 176
 177 #define COUNTER_CHECK(counter) \
 178         do { \
 179                 g_assert (counter._.max_working > 0); \
 180                 g_assert (counter._.starting >= 0); \
 181                 g_assert (counter._.working >= 0); \
 182         } while (0)
 183
 184 #define COUNTER_ATOMIC(var,block) \
 185         do { \
 186                 ThreadPoolWorkerCounter __old; \
 187                 do { \
 188                         __old = COUNTER_READ (); \
 189                         (var) = __old; \
 190                         { block; } \
 191                         COUNTER_CHECK (var); \
 192                 } while (InterlockedCompareExchange64 (&worker.counters.as_gint64, (var).as_gint64, __old.as_gint64) != __old.as_gint64); \
 193         } while (0)
 194
 195 static inline ThreadPoolWorkerCounter
 196 COUNTER_READ (void)
 197 {
 198         ThreadPoolWorkerCounter counter;
 199         counter.as_gint64 = InterlockedRead64 (&worker.counters.as_gint64);
 200         return counter;
 201 }
 202
 203 static gpointer
 204 rand_create (void)
 205 {
 206         mono_rand_open ();
 207         return mono_rand_init (NULL, 0);
 208 }
 209
 210 static guint32
 211 rand_next (gpointer *handle, guint32 min, guint32 max)
 212 {
 213         MonoError error;
 214         guint32 val;
 215         mono_rand_try_get_uint32 (handle, &val, min, max, &error);
 216         // FIXME handle error
 217         mono_error_assert_ok (&error);
 218         return val;
 219 }
 220
 221 static void
 222 destroy (gpointer data)
 223 {
 224 #if 0
 225         mono_coop_mutex_destroy (&worker.threads_lock);
 226         mono_coop_cond_destroy (&worker.parked_threads_cond);
 227
 228         mono_coop_mutex_destroy (&worker.work_items_lock);
 229
 230         mono_coop_mutex_destroy (&worker.worker_creation_lock);
 231
 232         mono_coop_mutex_destroy (&worker.heuristic_lock);
 233
 234         g_free (worker.cpu_usage_state);
 235 #endif
 236 }
 237
 238 void
 239 mono_threadpool_worker_init (void)
 240 {
 241         ThreadPoolHillClimbing *hc;
 242         const char *threads_per_cpu_env;
 243         gint threads_per_cpu;
 244         gint threads_count;
 245
 246         mono_refcount_init (&worker, destroy);
 247
 248         worker.threads = g_ptr_array_new ();
 249         mono_coop_mutex_init (&worker.threads_lock);
 250         worker.parked_threads_count = 0;
 251         mono_coop_cond_init (&worker.parked_threads_cond);
 252         mono_coop_cond_init (&worker.threads_exit_cond);
 253
 254         /* worker.work_items_size is inited to 0 */
 255         mono_coop_mutex_init (&worker.work_items_lock);
 256
 257         worker.worker_creation_current_second = -1;
 258         mono_coop_mutex_init (&worker.worker_creation_lock);
 259
 260         worker.heuristic_adjustment_interval = 10;
 261         mono_coop_mutex_init (&worker.heuristic_lock);
 262
 263         mono_rand_open ();
 264
 265         hc = &worker.heuristic_hill_climbing;
 266
 267         hc->wave_period = HILL_CLIMBING_WAVE_PERIOD;
 268         hc->max_thread_wave_magnitude = HILL_CLIMBING_MAX_WAVE_MAGNITUDE;
 269         hc->thread_magnitude_multiplier = (gdouble) HILL_CLIMBING_WAVE_MAGNITUDE_MULTIPLIER;
 270         hc->samples_to_measure = hc->wave_period * HILL_CLIMBING_WAVE_HISTORY_SIZE;
 271         hc->target_throughput_ratio = (gdouble) HILL_CLIMBING_BIAS;
 272         hc->target_signal_to_noise_ratio = (gdouble) HILL_CLIMBING_TARGET_SIGNAL_TO_NOISE_RATIO;
 273         hc->max_change_per_second = (gdouble) HILL_CLIMBING_MAX_CHANGE_PER_SECOND;
 274         hc->max_change_per_sample = (gdouble) HILL_CLIMBING_MAX_CHANGE_PER_SAMPLE;
 275         hc->sample_interval_low = HILL_CLIMBING_SAMPLE_INTERVAL_LOW;
 276         hc->sample_interval_high = HILL_CLIMBING_SAMPLE_INTERVAL_HIGH;
 277         hc->throughput_error_smoothing_factor = (gdouble) HILL_CLIMBING_ERROR_SMOOTHING_FACTOR;
 278         hc->gain_exponent = (gdouble) HILL_CLIMBING_GAIN_EXPONENT;
 279         hc->max_sample_error = (gdouble) HILL_CLIMBING_MAX_SAMPLE_ERROR_PERCENT;
 280         hc->current_control_setting = 0;
 281         hc->total_samples = 0;
 282         hc->last_thread_count = 0;
 283         hc->average_throughput_noise = 0;
 284         hc->elapsed_since_last_change = 0;
 285         hc->accumulated_completion_count = 0;
 286         hc->accumulated_sample_duration = 0;
 287         hc->samples = g_new0 (gdouble, hc->samples_to_measure);
 288         hc->thread_counts = g_new0 (gdouble, hc->samples_to_measure);
 289         hc->random_interval_generator = rand_create ();
 290         hc->current_sample_interval = rand_next (&hc->random_interval_generator, hc->sample_interval_low, hc->sample_interval_high);
 291
 292         if (!(threads_per_cpu_env = g_getenv ("MONO_THREADS_PER_CPU")))
 293                 threads_per_cpu = 1;
 294         else
 295                 threads_per_cpu = CLAMP (atoi (threads_per_cpu_env), 1, 50);
 296
 297         threads_count = mono_cpu_count () * threads_per_cpu;
 298
 299         worker.limit_worker_min = threads_count;
 300
 301 #if defined (PLATFORM_ANDROID) || defined (HOST_IOS)
 302         worker.limit_worker_max = CLAMP (threads_count * 100, MIN (threads_count, 200), MAX (threads_count, 200));
 303 #else
 304         worker.limit_worker_max = threads_count * 100;
 305 #endif
 306
 307         worker.counters._.max_working = worker.limit_worker_min;
 308
 309         worker.cpu_usage_state = g_new0 (MonoCpuUsageState, 1);
 310
 311         worker.suspended = FALSE;
 312
 313         worker.monitor_status = MONITOR_STATUS_NOT_RUNNING;
 314 }
 315
 316 void
 317 mono_threadpool_worker_cleanup (void)
 318 {
 319         MonoInternalThread *current;
 320
 321         /* we make the assumption along the code that we are
 322          * cleaning up only if the runtime is shutting down */
 323         g_assert (mono_runtime_is_shutting_down ());
 324
 325         current = mono_thread_internal_current ();
 326
 327         while (worker.monitor_status != MONITOR_STATUS_NOT_RUNNING)
 328                 mono_thread_info_sleep (1, NULL);
 329
 330         mono_coop_mutex_lock (&worker.threads_lock);
 331
 332         /* unpark all worker.parked_threads */
 333         mono_coop_cond_broadcast (&worker.parked_threads_cond);
 334
 335 #if 0
 336         for (;;) {
 337                 ThreadPoolWorkerCounter counter;
 338
 339                 counter = COUNTER_READ ();
 340                 if (counter._.starting + counter._.working + counter._.parked == 0)
 341                         break;
 342
 343                 if (counter._.starting + counter._.working + counter._.parked == 1) {
 344                         if (worker.threads->len == 1 && g_ptr_array_index (worker.threads, 0) == current) {
 345                                 /* We are waiting on ourselves */
 346                                 break;
 347                         }
 348                 }
 349
 350                 mono_coop_cond_wait (&worker.threads_exit_cond, &worker.threads_lock);
 351         }
 352 #endif
 353
 354         mono_coop_mutex_unlock (&worker.threads_lock);
 355
 356         mono_refcount_dec (&worker);
 357 }
 358
 359 static void
 360 work_item_lock (void)
 361 {
 362         mono_coop_mutex_lock (&worker.work_items_lock);
 363 }
 364
 365 static void
 366 work_item_unlock (void)
 367 {
 368         mono_coop_mutex_unlock (&worker.work_items_lock);
 369 }
 370
 371 static void
 372 work_item_push (MonoThreadPoolWorkerCallback callback, gpointer data)
 373 {
 374         ThreadPoolWorkItem work_item;
 375
 376         g_assert (callback);
 377
 378         work_item.callback = callback;
 379         work_item.data = data;
 380
 381         work_item_lock ();
 382
 383         g_assert (worker.work_items_count <= worker.work_items_size);
 384
 385         if (G_UNLIKELY (worker.work_items_count == worker.work_items_size)) {
 386                 worker.work_items_size += 64;
 387                 worker.work_items = g_renew (ThreadPoolWorkItem, worker.work_items, worker.work_items_size);
 388         }
 389
 390         g_assert (worker.work_items);
 391
 392         worker.work_items [worker.work_items_count ++] = work_item;
 393
 394         // printf ("[push] worker.work_items = %p, worker.work_items_count = %d, worker.work_items_size = %d\n",
 395         //      worker.work_items, worker.work_items_count, worker.work_items_size);
 396
 397         work_item_unlock ();
 398 }
 399
 400 static gboolean
 401 work_item_try_pop (ThreadPoolWorkItem *work_item)
 402 {
 403         g_assert (work_item);
 404
 405         work_item_lock ();
 406
 407         // printf ("[pop]  worker.work_items = %p, worker.work_items_count = %d, worker.work_items_size = %d\n",
 408         //      worker.work_items, worker.work_items_count, worker.work_items_size);
 409
 410         if (worker.work_items_count == 0) {
 411                 work_item_unlock ();
 412                 return FALSE;
 413         }
 414
 415         *work_item = worker.work_items [-- worker.work_items_count];
 416
 417         if (G_UNLIKELY (worker.work_items_count >= 64 * 3 && worker.work_items_count < worker.work_items_size / 2)) {
 418                 worker.work_items_size -= 64;
 419                 worker.work_items = g_renew (ThreadPoolWorkItem, worker.work_items, worker.work_items_size);
 420         }
 421
 422         work_item_unlock ();
 423
 424         return TRUE;
 425 }
 426
 427 static gint32
 428 work_item_count (void)
 429 {
 430         gint32 count;
 431
 432         work_item_lock ();
 433         count = worker.work_items_count;
 434         work_item_unlock ();
 435
 436         return count;
 437 }
 438
 439 static void worker_request (void);
 440
 441 void
 442 mono_threadpool_worker_enqueue (MonoThreadPoolWorkerCallback callback, gpointer data)
 443 {
 444         work_item_push (callback, data);
 445
 446         worker_request ();
 447 }
 448
 449 static void
 450 worker_wait_interrupt (gpointer unused)
 451 {
 452         mono_coop_mutex_lock (&worker.threads_lock);
 453         mono_coop_cond_signal (&worker.parked_threads_cond);
 454         mono_coop_mutex_unlock (&worker.threads_lock);
 455
 456         mono_refcount_dec (&worker);
 457 }
 458
 459 /* return TRUE if timeout, FALSE otherwise (worker unpark or interrupt) */
 460 static gboolean
 461 worker_park (void)
 462 {
 463         gboolean timeout = FALSE;
 464
 465         mono_trace (G_LOG_LEVEL_DEBUG, MONO_TRACE_THREADPOOL, "[%p] worker parking", mono_native_thread_id_get ());
 466
 467         mono_coop_mutex_lock (&worker.threads_lock);
 468
 469         if (!mono_runtime_is_shutting_down ()) {
 470                 static gpointer rand_handle = NULL;
 471                 MonoInternalThread *thread;
 472                 gboolean interrupted = FALSE;
 473                 ThreadPoolWorkerCounter counter;
 474
 475                 if (!rand_handle)
 476                         rand_handle = rand_create ();
 477                 g_assert (rand_handle);
 478
 479                 thread = mono_thread_internal_current ();
 480                 g_assert (thread);
 481
 482                 COUNTER_ATOMIC (counter, {
 483                         counter._.working --;
 484                         counter._.parked ++;
 485                 });
 486
 487                 worker.parked_threads_count += 1;
 488
 489                 mono_refcount_inc (&worker);
 490                 mono_thread_info_install_interrupt (worker_wait_interrupt, NULL, &interrupted);
 491                 if (interrupted) {
 492                         mono_refcount_dec (&worker);
 493                         goto done;
 494                 }
 495
 496                 if (mono_coop_cond_timedwait (&worker.parked_threads_cond, &worker.threads_lock, rand_next (&rand_handle, 5 * 1000, 60 * 1000)) != 0)
 497                         timeout = TRUE;
 498
 499                 mono_thread_info_uninstall_interrupt (&interrupted);
 500                 if (!interrupted)
 501                         mono_refcount_dec (&worker);
 502
 503 done:
 504                 worker.parked_threads_count -= 1;
 505
 506                 COUNTER_ATOMIC (counter, {
 507                         counter._.working ++;
 508                         counter._.parked --;
 509                 });
 510         }
 511
 512         mono_coop_mutex_unlock (&worker.threads_lock);
 513
 514         mono_trace (G_LOG_LEVEL_DEBUG, MONO_TRACE_THREADPOOL, "[%p] worker unparking, timeout? %s", mono_native_thread_id_get (), timeout ? "yes" : "no");
 515
 516         return timeout;
 517 }
 518
 519 static gboolean
 520 worker_try_unpark (void)
 521 {
 522         gboolean res = FALSE;
 523
 524         mono_trace (G_LOG_LEVEL_DEBUG, MONO_TRACE_THREADPOOL, "[%p] try unpark worker", mono_native_thread_id_get ());
 525
 526         mono_coop_mutex_lock (&worker.threads_lock);
 527         if (worker.parked_threads_count > 0) {
 528                 mono_coop_cond_signal (&worker.parked_threads_cond);
 529                 res = TRUE;
 530         }
 531         mono_coop_mutex_unlock (&worker.threads_lock);
 532
 533         mono_trace (G_LOG_LEVEL_DEBUG, MONO_TRACE_THREADPOOL, "[%p] try unpark worker, success? %s", mono_native_thread_id_get (), res ? "yes" : "no");
 534
 535         return res;
 536 }
 537
 538 static gsize WINAPI
 539 worker_thread (gpointer unused)
 540 {
 541         MonoInternalThread *thread;
 542         ThreadPoolWorkerCounter counter;
 543
 544         mono_trace (G_LOG_LEVEL_INFO, MONO_TRACE_THREADPOOL, "[%p] worker starting", mono_native_thread_id_get ());
 545
 546         COUNTER_ATOMIC (counter, {
 547                 counter._.starting --;
 548                 counter._.working ++;
 549         });
 550
 551         thread = mono_thread_internal_current ();
 552         g_assert (thread);
 553
 554         mono_coop_mutex_lock (&worker.threads_lock);
 555         g_ptr_array_add (worker.threads, thread);
 556         mono_coop_mutex_unlock (&worker.threads_lock);
 557
 558         while (!mono_runtime_is_shutting_down ()) {
 559                 ThreadPoolWorkItem work_item;
 560
 561                 if (mono_thread_interruption_checkpoint ())
 562                         continue;
 563
 564                 if (!work_item_try_pop (&work_item)) {
 565                         gboolean timeout;
 566
 567                         timeout = worker_park ();
 568                         if (timeout)
 569                                 break;
 570
 571                         continue;
 572                 }
 573
 574                 mono_trace (G_LOG_LEVEL_DEBUG, MONO_TRACE_THREADPOOL, "[%p] worker executing %p (%p)",
 575                         mono_native_thread_id_get (), work_item.callback, work_item.data);
 576
 577                 work_item.callback (work_item.data);
 578         }
 579
 580         mono_coop_mutex_lock (&worker.threads_lock);
 581
 582         COUNTER_ATOMIC (counter, {
 583                 counter._.working --;
 584         });
 585
 586         g_ptr_array_remove (worker.threads, thread);
 587
 588         mono_coop_cond_signal (&worker.threads_exit_cond);
 589
 590         mono_coop_mutex_unlock (&worker.threads_lock);
 591
 592         mono_trace (G_LOG_LEVEL_INFO, MONO_TRACE_THREADPOOL, "[%p] worker finishing", mono_native_thread_id_get ());
 593
 594         mono_refcount_dec (&worker);
 595
 596         return 0;
 597 }
 598
 599 static gboolean
 600 worker_try_create (void)
 601 {
 602         MonoError error;
 603         MonoInternalThread *thread;
 604         gint64 current_ticks;
 605         gint32 now;
 606         ThreadPoolWorkerCounter counter;
 607
 608         if (mono_runtime_is_shutting_down ())
 609                 return FALSE;
 610
 611         mono_coop_mutex_lock (&worker.worker_creation_lock);
 612
 613         mono_trace (G_LOG_LEVEL_DEBUG, MONO_TRACE_THREADPOOL, "[%p] try create worker", mono_native_thread_id_get ());
 614
 615         current_ticks = mono_100ns_ticks ();
 616         if (0 == current_ticks) {
 617                 g_warning ("failed to get 100ns ticks");
 618         } else {
 619                 now = current_ticks / (10 * 1000 * 1000);
 620                 if (worker.worker_creation_current_second != now) {
 621                         worker.worker_creation_current_second = now;
 622                         worker.worker_creation_current_count = 0;
 623                 } else {
 624                         g_assert (worker.worker_creation_current_count <= WORKER_CREATION_MAX_PER_SEC);
 625                         if (worker.worker_creation_current_count == WORKER_CREATION_MAX_PER_SEC) {
 626                                 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",
 627                                         mono_native_thread_id_get (), worker.worker_creation_current_count);
 628                                 mono_coop_mutex_unlock (&worker.worker_creation_lock);
 629                                 return FALSE;
 630                         }
 631                 }
 632         }
 633
 634         COUNTER_ATOMIC (counter, {
 635                 if (counter._.working >= counter._.max_working) {
 636                         mono_trace (G_LOG_LEVEL_DEBUG, MONO_TRACE_THREADPOOL, "[%p] try create worker, failed: maximum number of working threads reached",
 637                                 mono_native_thread_id_get ());
 638                         mono_coop_mutex_unlock (&worker.worker_creation_lock);
 639                         return FALSE;
 640                 }
 641                 counter._.starting ++;
 642         });
 643
 644         mono_refcount_inc (&worker);
 645         thread = mono_thread_create_internal (mono_get_root_domain (), worker_thread, NULL, TRUE, 0, &error);
 646         if (!thread) {
 647                 mono_trace (G_LOG_LEVEL_DEBUG, MONO_TRACE_THREADPOOL, "[%p] try create worker, failed: could not create thread due to %s", mono_native_thread_id_get (), mono_error_get_message (&error));
 648                 mono_error_cleanup (&error);
 649
 650                 COUNTER_ATOMIC (counter, {
 651                         counter._.starting --;
 652                 });
 653
 654                 mono_coop_mutex_unlock (&worker.worker_creation_lock);
 655
 656                 mono_refcount_dec (&worker);
 657
 658                 return FALSE;
 659         }
 660
 661         worker.worker_creation_current_count += 1;
 662
 663         mono_trace (G_LOG_LEVEL_DEBUG, MONO_TRACE_THREADPOOL, "[%p] try create worker, created %p, now = %d count = %d",
 664                 mono_native_thread_id_get (), (gpointer) thread->tid, now, worker.worker_creation_current_count);
 665
 666         mono_coop_mutex_unlock (&worker.worker_creation_lock);
 667         return TRUE;
 668 }
 669
 670 static void monitor_ensure_running (void);
 671
 672 static void
 673 worker_request (void)
 674 {
 675         if (worker.suspended)
 676                 return;
 677
 678         monitor_ensure_running ();
 679
 680         if (worker_try_unpark ()) {
 681                 mono_trace (G_LOG_LEVEL_DEBUG, MONO_TRACE_THREADPOOL, "[%p] request worker, unparked", mono_native_thread_id_get ());
 682                 return;
 683         }
 684
 685         if (worker_try_create ()) {
 686                 mono_trace (G_LOG_LEVEL_DEBUG, MONO_TRACE_THREADPOOL, "[%p] request worker, created", mono_native_thread_id_get ());
 687                 return;
 688         }
 689
 690         mono_trace (G_LOG_LEVEL_DEBUG, MONO_TRACE_THREADPOOL, "[%p] request worker, failed", mono_native_thread_id_get ());
 691 }
 692
 693 static gboolean
 694 monitor_should_keep_running (void)
 695 {
 696         static gint64 last_should_keep_running = -1;
 697
 698         g_assert (worker.monitor_status == MONITOR_STATUS_WAITING_FOR_REQUEST || worker.monitor_status == MONITOR_STATUS_REQUESTED);
 699
 700         if (InterlockedExchange (&worker.monitor_status, MONITOR_STATUS_WAITING_FOR_REQUEST) == MONITOR_STATUS_WAITING_FOR_REQUEST) {
 701                 gboolean should_keep_running = TRUE, force_should_keep_running = FALSE;
 702
 703                 if (mono_runtime_is_shutting_down ()) {
 704                         should_keep_running = FALSE;
 705                 } else {
 706                         if (work_item_count () == 0)
 707                                 should_keep_running = FALSE;
 708
 709                         if (!should_keep_running) {
 710                                 if (last_should_keep_running == -1 || mono_100ns_ticks () - last_should_keep_running < MONITOR_MINIMAL_LIFETIME * 1000 * 10) {
 711                                         should_keep_running = force_should_keep_running = TRUE;
 712                                 }
 713                         }
 714                 }
 715
 716                 if (should_keep_running) {
 717                         if (last_should_keep_running == -1 || !force_should_keep_running)
 718                                 last_should_keep_running = mono_100ns_ticks ();
 719                 } else {
 720                         last_should_keep_running = -1;
 721                         if (InterlockedCompareExchange (&worker.monitor_status, MONITOR_STATUS_NOT_RUNNING, MONITOR_STATUS_WAITING_FOR_REQUEST) == MONITOR_STATUS_WAITING_FOR_REQUEST)
 722                                 return FALSE;
 723                 }
 724         }
 725
 726         g_assert (worker.monitor_status == MONITOR_STATUS_WAITING_FOR_REQUEST || worker.monitor_status == MONITOR_STATUS_REQUESTED);
 727
 728         return TRUE;
 729 }
 730
 731 static gboolean
 732 monitor_sufficient_delay_since_last_dequeue (void)
 733 {
 734         gint64 threshold;
 735
 736         if (worker.cpu_usage < CPU_USAGE_LOW) {
 737                 threshold = MONITOR_INTERVAL;
 738         } else {
 739                 ThreadPoolWorkerCounter counter;
 740                 counter = COUNTER_READ ();
 741                 threshold = counter._.max_working * MONITOR_INTERVAL * 2;
 742         }
 743
 744         return mono_msec_ticks () >= worker.heuristic_last_dequeue + threshold;
 745 }
 746
 747 static void hill_climbing_force_change (gint16 new_thread_count, ThreadPoolHeuristicStateTransition transition);
 748
 749 static gsize WINAPI
 750 monitor_thread (gpointer unused)
 751 {
 752         MonoInternalThread *internal;
 753         guint i;
 754
 755         internal = mono_thread_internal_current ();
 756         g_assert (internal);
 757
 758         mono_cpu_usage (worker.cpu_usage_state);
 759
 760         // printf ("monitor_thread: start\n");
 761
 762         mono_trace (G_LOG_LEVEL_DEBUG, MONO_TRACE_THREADPOOL, "[%p] monitor thread, started", mono_native_thread_id_get ());
 763
 764         do {
 765                 ThreadPoolWorkerCounter counter;
 766                 gboolean limit_worker_max_reached;
 767                 gint32 interval_left = MONITOR_INTERVAL;
 768                 gint32 awake = 0; /* number of spurious awakes we tolerate before doing a round of rebalancing */
 769
 770                 g_assert (worker.monitor_status != MONITOR_STATUS_NOT_RUNNING);
 771
 772                 // counter = COUNTER_READ ();
 773                 // printf ("monitor_thread: starting = %d working = %d parked = %d max_working = %d\n",
 774                 //      counter._.starting, counter._.working, counter._.parked, counter._.max_working);
 775
 776                 do {
 777                         gint64 ts;
 778                         gboolean alerted = FALSE;
 779
 780                         if (mono_runtime_is_shutting_down ())
 781                                 break;
 782
 783                         ts = mono_msec_ticks ();
 784                         if (mono_thread_info_sleep (interval_left, &alerted) == 0)
 785                                 break;
 786                         interval_left -= mono_msec_ticks () - ts;
 787
 788                         g_assert (!(internal->state & ThreadState_StopRequested));
 789                         mono_thread_interruption_checkpoint ();
 790                 } while (interval_left > 0 && ++awake < 10);
 791
 792                 if (mono_runtime_is_shutting_down ())
 793                         continue;
 794
 795                 if (worker.suspended)
 796                         continue;
 797
 798                 if (work_item_count () == 0)
 799                         continue;
 800
 801                 worker.cpu_usage = mono_cpu_usage (worker.cpu_usage_state);
 802
 803                 if (!monitor_sufficient_delay_since_last_dequeue ())
 804                         continue;
 805
 806                 limit_worker_max_reached = FALSE;
 807
 808                 COUNTER_ATOMIC (counter, {
 809                         if (counter._.max_working >= worker.limit_worker_max) {
 810                                 limit_worker_max_reached = TRUE;
 811                                 break;
 812                         }
 813                         counter._.max_working ++;
 814                 });
 815
 816                 if (limit_worker_max_reached)
 817                         continue;
 818
 819                 hill_climbing_force_change (counter._.max_working, TRANSITION_STARVATION);
 820
 821                 for (i = 0; i < 5; ++i) {
 822                         if (mono_runtime_is_shutting_down ())
 823                                 break;
 824
 825                         if (worker_try_unpark ()) {
 826                                 mono_trace (G_LOG_LEVEL_DEBUG, MONO_TRACE_THREADPOOL, "[%p] monitor thread, unparked", mono_native_thread_id_get ());
 827                                 break;
 828                         }
 829
 830                         if (worker_try_create ()) {
 831                                 mono_trace (G_LOG_LEVEL_DEBUG, MONO_TRACE_THREADPOOL, "[%p] monitor thread, created", mono_native_thread_id_get ());
 832                                 break;
 833                         }
 834                 }
 835         } while (monitor_should_keep_running ());
 836
 837         // printf ("monitor_thread: stop\n");
 838
 839         mono_trace (G_LOG_LEVEL_DEBUG, MONO_TRACE_THREADPOOL, "[%p] monitor thread, finished", mono_native_thread_id_get ());
 840
 841         return 0;
 842 }
 843
 844 static void
 845 monitor_ensure_running (void)
 846 {
 847         MonoError error;
 848         for (;;) {
 849                 switch (worker.monitor_status) {
 850                 case MONITOR_STATUS_REQUESTED:
 851                         // printf ("monitor_thread: requested\n");
 852                         return;
 853                 case MONITOR_STATUS_WAITING_FOR_REQUEST:
 854                         // printf ("monitor_thread: waiting for request\n");
 855                         InterlockedCompareExchange (&worker.monitor_status, MONITOR_STATUS_REQUESTED, MONITOR_STATUS_WAITING_FOR_REQUEST);
 856                         break;
 857                 case MONITOR_STATUS_NOT_RUNNING:
 858                         // printf ("monitor_thread: not running\n");
 859                         if (mono_runtime_is_shutting_down ())
 860                                 return;
 861                         if (InterlockedCompareExchange (&worker.monitor_status, MONITOR_STATUS_REQUESTED, MONITOR_STATUS_NOT_RUNNING) == MONITOR_STATUS_NOT_RUNNING) {
 862                                 // printf ("monitor_thread: creating\n");
 863                                 if (!mono_thread_create_internal (mono_get_root_domain (), monitor_thread, NULL, TRUE, SMALL_STACK, &error)) {
 864                                         // printf ("monitor_thread: creating failed\n");
 865                                         worker.monitor_status = MONITOR_STATUS_NOT_RUNNING;
 866                                         mono_error_cleanup (&error);
 867                                 }
 868                                 return;
 869                         }
 870                         break;
 871                 default: g_assert_not_reached ();
 872                 }
 873         }
 874 }
 875
 876 static void
 877 hill_climbing_change_thread_count (gint16 new_thread_count, ThreadPoolHeuristicStateTransition transition)
 878 {
 879         ThreadPoolHillClimbing *hc;
 880
 881         hc = &worker.heuristic_hill_climbing;
 882
 883         mono_trace (G_LOG_LEVEL_INFO, MONO_TRACE_THREADPOOL, "[%p] hill climbing, change max number of threads %d", mono_native_thread_id_get (), new_thread_count);
 884
 885         hc->last_thread_count = new_thread_count;
 886         hc->current_sample_interval = rand_next (&hc->random_interval_generator, hc->sample_interval_low, hc->sample_interval_high);
 887         hc->elapsed_since_last_change = 0;
 888         hc->completions_since_last_change = 0;
 889 }
 890
 891 static void
 892 hill_climbing_force_change (gint16 new_thread_count, ThreadPoolHeuristicStateTransition transition)
 893 {
 894         ThreadPoolHillClimbing *hc;
 895
 896         hc = &worker.heuristic_hill_climbing;
 897
 898         if (new_thread_count != hc->last_thread_count) {
 899                 hc->current_control_setting += new_thread_count - hc->last_thread_count;
 900                 hill_climbing_change_thread_count (new_thread_count, transition);
 901         }
 902 }
 903
 904 static double_complex
 905 hill_climbing_get_wave_component (gdouble *samples, guint sample_count, gdouble period)
 906 {
 907         ThreadPoolHillClimbing *hc;
 908         gdouble w, cosine, sine, coeff, q0, q1, q2;
 909         guint i;
 910
 911         g_assert (sample_count >= period);
 912         g_assert (period >= 2);
 913
 914         hc = &worker.heuristic_hill_climbing;
 915
 916         w = 2.0 * M_PI / period;
 917         cosine = cos (w);
 918         sine = sin (w);
 919         coeff = 2.0 * cosine;
 920         q0 = q1 = q2 = 0;
 921
 922         for (i = 0; i < sample_count; ++i) {
 923                 q0 = coeff * q1 - q2 + samples [(hc->total_samples - sample_count + i) % hc->samples_to_measure];
 924                 q2 = q1;
 925                 q1 = q0;
 926         }
 927
 928         return mono_double_complex_scalar_div (mono_double_complex_make (q1 - q2 * cosine, (q2 * sine)), ((gdouble)sample_count));
 929 }
 930
 931 static gint16
 932 hill_climbing_update (gint16 current_thread_count, guint32 sample_duration, gint32 completions, gint64 *adjustment_interval)
 933 {
 934         ThreadPoolHillClimbing *hc;
 935         ThreadPoolHeuristicStateTransition transition;
 936         gdouble throughput;
 937         gdouble throughput_error_estimate;
 938         gdouble confidence;
 939         gdouble move;
 940         gdouble gain;
 941         gint sample_index;
 942         gint sample_count;
 943         gint new_thread_wave_magnitude;
 944         gint new_thread_count;
 945         double_complex thread_wave_component;
 946         double_complex throughput_wave_component;
 947         double_complex ratio;
 948
 949         g_assert (adjustment_interval);
 950
 951         hc = &worker.heuristic_hill_climbing;
 952
 953         /* If someone changed the thread count without telling us, update our records accordingly. */
 954         if (current_thread_count != hc->last_thread_count)
 955                 hill_climbing_force_change (current_thread_count, TRANSITION_INITIALIZING);
 956
 957         /* Update the cumulative stats for this thread count */
 958         hc->elapsed_since_last_change += sample_duration;
 959         hc->completions_since_last_change += completions;
 960
 961         /* Add in any data we've already collected about this sample */
 962         sample_duration += hc->accumulated_sample_duration;
 963         completions += hc->accumulated_completion_count;
 964
 965         /* We need to make sure we're collecting reasonably accurate data. Since we're just counting the end
 966          * of each work item, we are goinng to be missing some data about what really happened during the
 967          * sample interval. The count produced by each thread includes an initial work item that may have
 968          * started well before the start of the interval, and each thread may have been running some new
 969          * work item for some time before the end of the interval, which did not yet get counted. So
 970          * our count is going to be off by +/- threadCount workitems.
 971          *
 972          * The exception is that the thread that reported to us last time definitely wasn't running any work
 973          * at that time, and the thread that's reporting now definitely isn't running a work item now. So
 974          * we really only need to consider threadCount-1 threads.
 975          *
 976          * Thus the percent error in our count is +/- (threadCount-1)/numCompletions.
 977          *
 978          * We cannot rely on the frequency-domain analysis we'll be doing later to filter out this error, because
 979          * of the way it accumulates over time. If this sample is off by, say, 33% in the negative direction,
 980          * then the next one likely will be too. The one after that will include the sum of the completions
 981          * we missed in the previous samples, and so will be 33% positive. So every three samples we'll have
 982          * two "low" samples and one "high" sample. This will appear as periodic variation right in the frequency
 983          * range we're targeting, which will not be filtered by the frequency-domain translation. */
 984         if (hc->total_samples > 0 && ((current_thread_count - 1.0) / completions) >= hc->max_sample_error) {
 985                 /* Not accurate enough yet. Let's accumulate the data so
 986                  * far, and tell the ThreadPoolWorker to collect a little more. */
 987                 hc->accumulated_sample_duration = sample_duration;
 988                 hc->accumulated_completion_count = completions;
 989                 *adjustment_interval = 10;
 990                 return current_thread_count;
 991         }
 992
 993         /* We've got enouugh data for our sample; reset our accumulators for next time. */
 994         hc->accumulated_sample_duration = 0;
 995         hc->accumulated_completion_count = 0;
 996
 997         /* Add the current thread count and throughput sample to our history. */
 998         throughput = ((gdouble) completions) / sample_duration;
 999
1000         sample_index = hc->total_samples % hc->samples_to_measure;
1001         hc->samples [sample_index] = throughput;
1002         hc->thread_counts [sample_index] = current_thread_count;
1003         hc->total_samples ++;
1004
1005         /* Set up defaults for our metrics. */
1006         thread_wave_component = mono_double_complex_make(0, 0);
1007         throughput_wave_component = mono_double_complex_make(0, 0);
1008         throughput_error_estimate = 0;
1009         ratio = mono_double_complex_make(0, 0);
1010         confidence = 0;
1011
1012         transition = TRANSITION_WARMUP;
1013
1014         /* How many samples will we use? It must be at least the three wave periods we're looking for, and it must also
1015          * be a whole multiple of the primary wave's period; otherwise the frequency we're looking for will fall between
1016          * two frequency bands in the Fourier analysis, and we won't be able to measure it accurately. */
1017         sample_count = ((gint) MIN (hc->total_samples - 1, hc->samples_to_measure) / hc->wave_period) * hc->wave_period;
1018
1019         if (sample_count > hc->wave_period) {
1020                 guint i;
1021                 gdouble average_throughput;
1022                 gdouble average_thread_count;
1023                 gdouble sample_sum = 0;
1024                 gdouble thread_sum = 0;
1025
1026                 /* Average the throughput and thread count samples, so we can scale the wave magnitudes later. */
1027                 for (i = 0; i < sample_count; ++i) {
1028                         guint j = (hc->total_samples - sample_count + i) % hc->samples_to_measure;
1029                         sample_sum += hc->samples [j];
1030                         thread_sum += hc->thread_counts [j];
1031                 }
1032
1033                 average_throughput = sample_sum / sample_count;
1034                 average_thread_count = thread_sum / sample_count;
1035
1036                 if (average_throughput > 0 && average_thread_count > 0) {
1037                         gdouble noise_for_confidence, adjacent_period_1, adjacent_period_2;
1038
1039                         /* Calculate the periods of the adjacent frequency bands we'll be using to
1040                          * measure noise levels. We want the two adjacent Fourier frequency bands. */
1041                         adjacent_period_1 = sample_count / (((gdouble) sample_count) / ((gdouble) hc->wave_period) + 1);
1042                         adjacent_period_2 = sample_count / (((gdouble) sample_count) / ((gdouble) hc->wave_period) - 1);
1043
1044                         /* Get the the three different frequency components of the throughput (scaled by average
1045                          * throughput). Our "error" estimate (the amount of noise that might be present in the
1046                          * frequency band we're really interested in) is the average of the adjacent bands. */
1047                         throughput_wave_component = mono_double_complex_scalar_div (hill_climbing_get_wave_component (hc->samples, sample_count, hc->wave_period), average_throughput);
1048                         throughput_error_estimate = cabs (mono_double_complex_scalar_div (hill_climbing_get_wave_component (hc->samples, sample_count, adjacent_period_1), average_throughput));
1049
1050                         if (adjacent_period_2 <= sample_count) {
1051                                 throughput_error_estimate = MAX (throughput_error_estimate, cabs (mono_double_complex_scalar_div (hill_climbing_get_wave_component (
1052                                         hc->samples, sample_count, adjacent_period_2), average_throughput)));
1053                         }
1054
1055                         /* Do the same for the thread counts, so we have something to compare to. We don't
1056                          * measure thread count noise, because there is none; these are exact measurements. */
1057                         thread_wave_component = mono_double_complex_scalar_div (hill_climbing_get_wave_component (hc->thread_counts, sample_count, hc->wave_period), average_thread_count);
1058
1059                         /* Update our moving average of the throughput noise. We'll use this
1060                          * later as feedback to determine the new size of the thread wave. */
1061                         if (hc->average_throughput_noise == 0) {
1062                                 hc->average_throughput_noise = throughput_error_estimate;
1063                         } else {
1064                                 hc->average_throughput_noise = (hc->throughput_error_smoothing_factor * throughput_error_estimate)
1065                                         + ((1.0 + hc->throughput_error_smoothing_factor) * hc->average_throughput_noise);
1066                         }
1067
1068                         if (cabs (thread_wave_component) > 0) {
1069                                 /* Adjust the throughput wave so it's centered around the target wave,
1070                                  * and then calculate the adjusted throughput/thread ratio. */
1071                                 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);
1072                                 transition = TRANSITION_CLIMBING_MOVE;
1073                         } else {
1074                                 ratio = mono_double_complex_make (0, 0);
1075                                 transition = TRANSITION_STABILIZING;
1076                         }
1077
1078                         noise_for_confidence = MAX (hc->average_throughput_noise, throughput_error_estimate);
1079                         if (noise_for_confidence > 0) {
1080                                 confidence = cabs (thread_wave_component) / noise_for_confidence / hc->target_signal_to_noise_ratio;
1081                         } else {
1082                                 /* there is no noise! */
1083                                 confidence = 1.0;
1084                         }
1085                 }
1086         }
1087
1088         /* We use just the real part of the complex ratio we just calculated. If the throughput signal
1089          * is exactly in phase with the thread signal, this will be the same as taking the magnitude of
1090          * the complex move and moving that far up. If they're 180 degrees out of phase, we'll move
1091          * backward (because this indicates that our changes are having the opposite of the intended effect).
1092          * If they're 90 degrees out of phase, we won't move at all, because we can't tell wether we're
1093          * having a negative or positive effect on throughput. */
1094         move = creal (ratio);
1095         move = CLAMP (move, -1.0, 1.0);
1096
1097         /* Apply our confidence multiplier. */
1098         move *= CLAMP (confidence, -1.0, 1.0);
1099
1100         /* Now apply non-linear gain, such that values around zero are attenuated, while higher values
1101          * are enhanced. This allows us to move quickly if we're far away from the target, but more slowly
1102         * if we're getting close, giving us rapid ramp-up without wild oscillations around the target. */
1103         gain = hc->max_change_per_second * sample_duration;
1104         move = pow (fabs (move), hc->gain_exponent) * (move >= 0.0 ? 1 : -1) * gain;
1105         move = MIN (move, hc->max_change_per_sample);
1106
1107         /* If the result was positive, and CPU is > 95%, refuse the move. */
1108         if (move > 0.0 && worker.cpu_usage > CPU_USAGE_HIGH)
1109                 move = 0.0;
1110
1111         /* Apply the move to our control setting. */
1112         hc->current_control_setting += move;
1113
1114         /* Calculate the new thread wave magnitude, which is based on the moving average we've been keeping of the
1115          * throughput error.  This average starts at zero, so we'll start with a nice safe little wave at first. */
1116         new_thread_wave_magnitude = (gint)(0.5 + (hc->current_control_setting * hc->average_throughput_noise
1117                 * hc->target_signal_to_noise_ratio * hc->thread_magnitude_multiplier * 2.0));
1118         new_thread_wave_magnitude = CLAMP (new_thread_wave_magnitude, 1, hc->max_thread_wave_magnitude);
1119
1120         /* Make sure our control setting is within the ThreadPoolWorker's limits. */
1121         hc->current_control_setting = CLAMP (hc->current_control_setting, worker.limit_worker_min, worker.limit_worker_max - new_thread_wave_magnitude);
1122
1123         /* Calculate the new thread count (control setting + square wave). */
1124         new_thread_count = (gint)(hc->current_control_setting + new_thread_wave_magnitude * ((hc->total_samples / (hc->wave_period / 2)) % 2));
1125
1126         /* Make sure the new thread count doesn't exceed the ThreadPoolWorker's limits. */
1127         new_thread_count = CLAMP (new_thread_count, worker.limit_worker_min, worker.limit_worker_max);
1128
1129         if (new_thread_count != current_thread_count)
1130                 hill_climbing_change_thread_count (new_thread_count, transition);
1131
1132         if (creal (ratio) < 0.0 && new_thread_count == worker.limit_worker_min)
1133                 *adjustment_interval = (gint)(0.5 + hc->current_sample_interval * (10.0 * MAX (-1.0 * creal (ratio), 1.0)));
1134         else
1135                 *adjustment_interval = hc->current_sample_interval;
1136
1137         return new_thread_count;
1138 }
1139
1140 static gboolean
1141 heuristic_should_adjust (void)
1142 {
1143         if (worker.heuristic_last_dequeue > worker.heuristic_last_adjustment + worker.heuristic_adjustment_interval) {
1144                 ThreadPoolWorkerCounter counter;
1145                 counter = COUNTER_READ ();
1146                 if (counter._.working <= counter._.max_working)
1147                         return TRUE;
1148         }
1149
1150         return FALSE;
1151 }
1152
1153 static void
1154 heuristic_adjust (void)
1155 {
1156         if (mono_coop_mutex_trylock (&worker.heuristic_lock) == 0) {
1157                 gint32 completions = InterlockedExchange (&worker.heuristic_completions, 0);
1158                 gint64 sample_end = mono_msec_ticks ();
1159                 gint64 sample_duration = sample_end - worker.heuristic_sample_start;
1160
1161                 if (sample_duration >= worker.heuristic_adjustment_interval / 2) {
1162                         ThreadPoolWorkerCounter counter;
1163                         gint16 new_thread_count;
1164
1165                         counter = COUNTER_READ ();
1166                         new_thread_count = hill_climbing_update (counter._.max_working, sample_duration, completions, &worker.heuristic_adjustment_interval);
1167
1168                         COUNTER_ATOMIC (counter, {
1169                                 counter._.max_working = new_thread_count;
1170                         });
1171
1172                         if (new_thread_count > counter._.max_working)
1173                                 worker_request ();
1174
1175                         worker.heuristic_sample_start = sample_end;
1176                         worker.heuristic_last_adjustment = mono_msec_ticks ();
1177                 }
1178
1179                 mono_coop_mutex_unlock (&worker.heuristic_lock);
1180         }
1181 }
1182
1183 static void
1184 heuristic_notify_work_completed (void)
1185 {
1186         InterlockedIncrement (&worker.heuristic_completions);
1187         worker.heuristic_last_dequeue = mono_msec_ticks ();
1188
1189         if (heuristic_should_adjust ())
1190                 heuristic_adjust ();
1191 }
1192
1193 gboolean
1194 mono_threadpool_worker_notify_completed (void)
1195 {
1196         ThreadPoolWorkerCounter counter;
1197
1198         heuristic_notify_work_completed ();
1199
1200         counter = COUNTER_READ ();
1201         return counter._.working <= counter._.max_working;
1202 }
1203
1204 gint32
1205 mono_threadpool_worker_get_min (void)
1206 {
1207         return worker.limit_worker_min;
1208 }
1209
1210 gboolean
1211 mono_threadpool_worker_set_min (gint32 value)
1212 {
1213         if (value <= 0 || value > worker.limit_worker_max)
1214                 return FALSE;
1215
1216         worker.limit_worker_min = value;
1217         return TRUE;
1218 }
1219
1220 gint32
1221 mono_threadpool_worker_get_max (void)
1222 {
1223         return worker.limit_worker_max;
1224 }
1225
1226 gboolean
1227 mono_threadpool_worker_set_max (gint32 value)
1228 {
1229         gint32 cpu_count;
1230
1231         cpu_count = mono_cpu_count ();
1232         if (value < worker.limit_worker_min || value < cpu_count)
1233                 return FALSE;
1234
1235         if (value < worker.limit_worker_min || value < cpu_count)
1236                 return FALSE;
1237
1238         worker.limit_worker_max = value;
1239         return TRUE;
1240 }
1241
1242 void
1243 mono_threadpool_worker_set_suspended (gboolean suspended)
1244 {
1245         worker.suspended = suspended;
1246         if (!suspended)
1247                 worker_request ();
1248 }