mono/metadata/threadpool-worker-default.c

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