1 /*
   2  * Copyright (c) 2010, 2013, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 #include "runtime/advancedThresholdPolicy.hpp"
  27 #include "runtime/simpleThresholdPolicy.inline.hpp"
  28 
  29 #ifdef TIERED
  30 // Print an event.
  31 void AdvancedThresholdPolicy::print_specific(EventType type, methodHandle mh, methodHandle imh,
  32                                              int bci, CompLevel level) {
  33   tty->print(" rate=");
  34   if (mh->prev_time() == 0) tty->print("n/a");
  35   else tty->print("%f", mh->rate());
  36 
  37   tty->print(" k=%.2lf,%.2lf", threshold_scale(CompLevel_full_profile, Tier3LoadFeedback),
  38                                threshold_scale(CompLevel_full_optimization, Tier4LoadFeedback));
  39 
  40 }
  41 
  42 void AdvancedThresholdPolicy::initialize() {
  43   // Turn on ergonomic compiler count selection
  44   if (FLAG_IS_DEFAULT(CICompilerCountPerCPU) && FLAG_IS_DEFAULT(CICompilerCount)) {
  45     FLAG_SET_DEFAULT(CICompilerCountPerCPU, true);
  46   }
  47   int count = CICompilerCount;
  48   if (CICompilerCountPerCPU) {
  49     // Simple log n seems to grow too slowly for tiered, try something faster: log n * log log n
  50     int log_cpu = log2_intptr(os::active_processor_count());
  51     int loglog_cpu = log2_intptr(MAX2(log_cpu, 1));
  52     count = MAX2(log_cpu * loglog_cpu, 1) * 3 / 2;
  53   }
  54 
  55   assert ((c1_count() == 0) && (c2_count() == 0), "Must be initialized to 0");
  56   // Set number of compiler threads only if we also use the compiler
  57   if (Arguments::mode() != Arguments::_int) {
  58     set_c1_count(MAX2(count / 3, 1));
  59     set_c2_count(MAX2(count - count / 3, 1));
  60   }
  61 
  62   // Some inlining tuning
  63 #ifdef X86
  64   if (FLAG_IS_DEFAULT(InlineSmallCode)) {
  65     FLAG_SET_DEFAULT(InlineSmallCode, 2000);
  66   }
  67 #endif
  68 
  69 #ifdef SPARC
  70   if (FLAG_IS_DEFAULT(InlineSmallCode)) {
  71     FLAG_SET_DEFAULT(InlineSmallCode, 2500);
  72   }
  73 #endif
  74 
  75   set_increase_threshold_at_ratio();
  76   set_start_time(os::javaTimeMillis());
  77 }
  78 
  79 // update_rate() is called from select_task() while holding a compile queue lock.
  80 void AdvancedThresholdPolicy::update_rate(jlong t, Method* m) {
  81   JavaThread* THREAD = JavaThread::current();
  82   if (is_old(m)) {
  83     // We don't remove old methods from the queue,
  84     // so we can just zero the rate.
  85     m->set_rate(0, THREAD);
  86     return;
  87   }
  88 
  89   // We don't update the rate if we've just came out of a safepoint.
  90   // delta_s is the time since last safepoint in milliseconds.
  91   jlong delta_s = t - SafepointSynchronize::end_of_last_safepoint();
  92   jlong delta_t = t - (m->prev_time() != 0 ? m->prev_time() : start_time()); // milliseconds since the last measurement
  93   // How many events were there since the last time?
  94   int event_count = m->invocation_count() + m->backedge_count();
  95   int delta_e = event_count - m->prev_event_count();
  96 
  97   // We should be running for at least 1ms.
  98   if (delta_s >= TieredRateUpdateMinTime) {
  99     // And we must've taken the previous point at least 1ms before.
 100     if (delta_t >= TieredRateUpdateMinTime && delta_e > 0) {
 101       m->set_prev_time(t, THREAD);
 102       m->set_prev_event_count(event_count, THREAD);
 103       m->set_rate((float)delta_e / (float)delta_t, THREAD); // Rate is events per millisecond
 104     } else
 105       if (delta_t > TieredRateUpdateMaxTime && delta_e == 0) {
 106         // If nothing happened for 25ms, zero the rate. Don't modify prev values.
 107         m->set_rate(0, THREAD);
 108       }
 109   }
 110 }
 111 
 112 // Check if this method has been stale from a given number of milliseconds.
 113 // See select_task().
 114 bool AdvancedThresholdPolicy::is_stale(jlong t, jlong timeout, Method* m) {
 115   jlong delta_s = t - SafepointSynchronize::end_of_last_safepoint();
 116   jlong delta_t = t - m->prev_time();
 117   if (delta_t > timeout && delta_s > timeout) {
 118     int event_count = m->invocation_count() + m->backedge_count();
 119     int delta_e = event_count - m->prev_event_count();
 120     // Return true if there were no events.
 121     return delta_e == 0;
 122   }
 123   return false;
 124 }
 125 
 126 // We don't remove old methods from the compile queue even if they have
 127 // very low activity. See select_task().
 128 bool AdvancedThresholdPolicy::is_old(Method* method) {
 129   return method->invocation_count() > 50000 || method->backedge_count() > 500000;
 130 }
 131 
 132 double AdvancedThresholdPolicy::weight(Method* method) {
 133   return (method->rate() + 1) * ((method->invocation_count() + 1) *  (method->backedge_count() + 1));
 134 }
 135 
 136 // Apply heuristics and return true if x should be compiled before y
 137 bool AdvancedThresholdPolicy::compare_methods(Method* x, Method* y) {
 138   if (x->highest_comp_level() > y->highest_comp_level()) {
 139     // recompilation after deopt
 140     return true;
 141   } else
 142     if (x->highest_comp_level() == y->highest_comp_level()) {
 143       if (weight(x) > weight(y)) {
 144         return true;
 145       }
 146     }
 147   return false;
 148 }
 149 
 150 // Is method profiled enough?
 151 bool AdvancedThresholdPolicy::is_method_profiled(Method* method) {
 152   MethodData* mdo = method->method_data();
 153   if (mdo != NULL) {
 154     int i = mdo->invocation_count_delta();
 155     int b = mdo->backedge_count_delta();
 156     return call_predicate_helper<CompLevel_full_profile>(i, b, 1);
 157   }
 158   return false;
 159 }
 160 
 161 // Called with the queue locked and with at least one element
 162 CompileTask* AdvancedThresholdPolicy::select_task(CompileQueue* compile_queue) {
 163   CompileTask *max_task = NULL;
 164   Method* max_method = NULL;
 165   jlong t = os::javaTimeMillis();
 166   // Iterate through the queue and find a method with a maximum rate.
 167   for (CompileTask* task = compile_queue->first(); task != NULL;) {
 168     CompileTask* next_task = task->next();
 169     Method* method = task->method();
 170     MethodData* mdo = method->method_data();
 171     update_rate(t, method);
 172     if (max_task == NULL) {
 173       max_task = task;
 174       max_method = method;
 175     } else {
 176       // If a method has been stale for some time, remove it from the queue.
 177       if (is_stale(t, TieredCompileTaskTimeout, method) && !is_old(method)) {
 178         if (PrintTieredEvents) {
 179           print_event(REMOVE_FROM_QUEUE, method, method, task->osr_bci(), (CompLevel)task->comp_level());
 180         }
 181         CompileTaskWrapper ctw(task); // Frees the task
 182         compile_queue->remove(task);
 183         method->clear_queued_for_compilation();
 184         task = next_task;
 185         continue;
 186       }
 187 
 188       // Select a method with a higher rate
 189       if (compare_methods(method, max_method)) {
 190         max_task = task;
 191         max_method = method;
 192       }
 193     }
 194     task = next_task;
 195   }
 196 
 197   if (max_task->comp_level() == CompLevel_full_profile && TieredStopAtLevel > CompLevel_full_profile
 198       && is_method_profiled(max_method)) {
 199     max_task->set_comp_level(CompLevel_limited_profile);
 200     if (PrintTieredEvents) {
 201       print_event(UPDATE_IN_QUEUE, max_method, max_method, max_task->osr_bci(), (CompLevel)max_task->comp_level());
 202     }
 203   }
 204 
 205   return max_task;
 206 }
 207 
 208 double AdvancedThresholdPolicy::threshold_scale(CompLevel level, int feedback_k) {
 209   double queue_size = CompileBroker::queue_size(level);
 210   int comp_count = compiler_count(level);
 211   double k = queue_size / (feedback_k * comp_count) + 1;
 212 
 213   // Increase C1 compile threshold when the code cache is filled more
 214   // than specified by IncreaseFirstTierCompileThresholdAt percentage.
 215   // The main intention is to keep enough free space for C2 compiled code
 216   // to achieve peak performance if the code cache is under stress.
 217   if ((TieredStopAtLevel == CompLevel_full_optimization) && (level != CompLevel_full_optimization))  {
 218     double current_reverse_free_ratio = CodeCache::reverse_free_ratio();
 219     if (current_reverse_free_ratio > _increase_threshold_at_ratio) {
 220       k *= exp(current_reverse_free_ratio - _increase_threshold_at_ratio);
 221     }
 222   }
 223   return k;
 224 }
 225 
 226 // Call and loop predicates determine whether a transition to a higher
 227 // compilation level should be performed (pointers to predicate functions
 228 // are passed to common()).
 229 // Tier?LoadFeedback is basically a coefficient that determines of
 230 // how many methods per compiler thread can be in the queue before
 231 // the threshold values double.
 232 bool AdvancedThresholdPolicy::loop_predicate(int i, int b, CompLevel cur_level) {
 233   switch(cur_level) {
 234   case CompLevel_none:
 235   case CompLevel_limited_profile: {
 236     double k = threshold_scale(CompLevel_full_profile, Tier3LoadFeedback);
 237     return loop_predicate_helper<CompLevel_none>(i, b, k);
 238   }
 239   case CompLevel_full_profile: {
 240     double k = threshold_scale(CompLevel_full_optimization, Tier4LoadFeedback);
 241     return loop_predicate_helper<CompLevel_full_profile>(i, b, k);
 242   }
 243   default:
 244     return true;
 245   }
 246 }
 247 
 248 bool AdvancedThresholdPolicy::call_predicate(int i, int b, CompLevel cur_level) {
 249   switch(cur_level) {
 250   case CompLevel_none:
 251   case CompLevel_limited_profile: {
 252     double k = threshold_scale(CompLevel_full_profile, Tier3LoadFeedback);
 253     return call_predicate_helper<CompLevel_none>(i, b, k);
 254   }
 255   case CompLevel_full_profile: {
 256     double k = threshold_scale(CompLevel_full_optimization, Tier4LoadFeedback);
 257     return call_predicate_helper<CompLevel_full_profile>(i, b, k);
 258   }
 259   default:
 260     return true;
 261   }
 262 }
 263 
 264 // If a method is old enough and is still in the interpreter we would want to
 265 // start profiling without waiting for the compiled method to arrive.
 266 // We also take the load on compilers into the account.
 267 bool AdvancedThresholdPolicy::should_create_mdo(Method* method, CompLevel cur_level) {
 268   if (cur_level == CompLevel_none &&
 269       CompileBroker::queue_size(CompLevel_full_optimization) <=
 270       Tier3DelayOn * compiler_count(CompLevel_full_optimization)) {
 271     int i = method->invocation_count();
 272     int b = method->backedge_count();
 273     double k = Tier0ProfilingStartPercentage / 100.0;
 274     return call_predicate_helper<CompLevel_none>(i, b, k) || loop_predicate_helper<CompLevel_none>(i, b, k);
 275   }
 276   return false;
 277 }
 278 
 279 // Inlining control: if we're compiling a profiled method with C1 and the callee
 280 // is known to have OSRed in a C2 version, don't inline it.
 281 bool AdvancedThresholdPolicy::should_not_inline(ciEnv* env, ciMethod* callee) {
 282   CompLevel comp_level = (CompLevel)env->comp_level();
 283   if (comp_level == CompLevel_full_profile ||
 284       comp_level == CompLevel_limited_profile) {
 285     return callee->highest_osr_comp_level() == CompLevel_full_optimization;
 286   }
 287   return false;
 288 }
 289 
 290 // Create MDO if necessary.
 291 void AdvancedThresholdPolicy::create_mdo(methodHandle mh, JavaThread* THREAD) {
 292   if (mh->is_native() || mh->is_abstract() || mh->is_accessor()) return;
 293   if (mh->method_data() == NULL) {
 294     Method::build_interpreter_method_data(mh, CHECK_AND_CLEAR);
 295   }
 296 }
 297 
 298 
 299 /*
 300  * Method states:
 301  *   0 - interpreter (CompLevel_none)
 302  *   1 - pure C1 (CompLevel_simple)
 303  *   2 - C1 with invocation and backedge counting (CompLevel_limited_profile)
 304  *   3 - C1 with full profiling (CompLevel_full_profile)
 305  *   4 - C2 (CompLevel_full_optimization)
 306  *
 307  * Common state transition patterns:
 308  * a. 0 -> 3 -> 4.
 309  *    The most common path. But note that even in this straightforward case
 310  *    profiling can start at level 0 and finish at level 3.
 311  *
 312  * b. 0 -> 2 -> 3 -> 4.
 313  *    This case occures when the load on C2 is deemed too high. So, instead of transitioning
 314  *    into state 3 directly and over-profiling while a method is in the C2 queue we transition to
 315  *    level 2 and wait until the load on C2 decreases. This path is disabled for OSRs.
 316  *
 317  * c. 0 -> (3->2) -> 4.
 318  *    In this case we enqueue a method for compilation at level 3, but the C1 queue is long enough
 319  *    to enable the profiling to fully occur at level 0. In this case we change the compilation level
 320  *    of the method to 2, because it'll allow it to run much faster without full profiling while c2
 321  *    is compiling.
 322  *
 323  * d. 0 -> 3 -> 1 or 0 -> 2 -> 1.
 324  *    After a method was once compiled with C1 it can be identified as trivial and be compiled to
 325  *    level 1. These transition can also occur if a method can't be compiled with C2 but can with C1.
 326  *
 327  * e. 0 -> 4.
 328  *    This can happen if a method fails C1 compilation (it will still be profiled in the interpreter)
 329  *    or because of a deopt that didn't require reprofiling (compilation won't happen in this case because
 330  *    the compiled version already exists).
 331  *
 332  * Note that since state 0 can be reached from any other state via deoptimization different loops
 333  * are possible.
 334  *
 335  */
 336 
 337 // Common transition function. Given a predicate determines if a method should transition to another level.
 338 CompLevel AdvancedThresholdPolicy::common(Predicate p, Method* method, CompLevel cur_level, bool disable_feedback) {
 339   CompLevel next_level = cur_level;
 340   int i = method->invocation_count();
 341   int b = method->backedge_count();
 342 
 343   if (is_trivial(method)) {
 344     next_level = CompLevel_simple;
 345   } else {
 346     switch(cur_level) {
 347     case CompLevel_none:
 348       // If we were at full profile level, would we switch to full opt?
 349       if (common(p, method, CompLevel_full_profile, disable_feedback) == CompLevel_full_optimization) {
 350         next_level = CompLevel_full_optimization;
 351       } else if ((this->*p)(i, b, cur_level)) {
 352         // C1-generated fully profiled code is about 30% slower than the limited profile
 353         // code that has only invocation and backedge counters. The observation is that
 354         // if C2 queue is large enough we can spend too much time in the fully profiled code
 355         // while waiting for C2 to pick the method from the queue. To alleviate this problem
 356         // we introduce a feedback on the C2 queue size. If the C2 queue is sufficiently long
 357         // we choose to compile a limited profiled version and then recompile with full profiling
 358         // when the load on C2 goes down.
 359         if (!disable_feedback && CompileBroker::queue_size(CompLevel_full_optimization) >
 360                                  Tier3DelayOn * compiler_count(CompLevel_full_optimization)) {
 361           next_level = CompLevel_limited_profile;
 362         } else {
 363           next_level = CompLevel_full_profile;
 364         }
 365       }
 366       break;
 367     case CompLevel_limited_profile:
 368       if (is_method_profiled(method)) {
 369         // Special case: we got here because this method was fully profiled in the interpreter.
 370         next_level = CompLevel_full_optimization;
 371       } else {
 372         MethodData* mdo = method->method_data();
 373         if (mdo != NULL) {
 374           if (mdo->would_profile()) {
 375             if (disable_feedback || (CompileBroker::queue_size(CompLevel_full_optimization) <=
 376                                      Tier3DelayOff * compiler_count(CompLevel_full_optimization) &&
 377                                      (this->*p)(i, b, cur_level))) {
 378               next_level = CompLevel_full_profile;
 379             }
 380           } else {
 381             next_level = CompLevel_full_optimization;
 382           }
 383         }
 384       }
 385       break;
 386     case CompLevel_full_profile:
 387       {
 388         MethodData* mdo = method->method_data();
 389         if (mdo != NULL) {
 390           if (mdo->would_profile()) {
 391             int mdo_i = mdo->invocation_count_delta();
 392             int mdo_b = mdo->backedge_count_delta();
 393             if ((this->*p)(mdo_i, mdo_b, cur_level)) {
 394               next_level = CompLevel_full_optimization;
 395             }
 396           } else {
 397             next_level = CompLevel_full_optimization;
 398           }
 399         }
 400       }
 401       break;
 402     }
 403   }
 404   return MIN2(next_level, (CompLevel)TieredStopAtLevel);
 405 }
 406 
 407 // Determine if a method should be compiled with a normal entry point at a different level.
 408 CompLevel AdvancedThresholdPolicy::call_event(Method* method, CompLevel cur_level) {
 409   CompLevel osr_level = MIN2((CompLevel) method->highest_osr_comp_level(),
 410                              common(&AdvancedThresholdPolicy::loop_predicate, method, cur_level, true));
 411   CompLevel next_level = common(&AdvancedThresholdPolicy::call_predicate, method, cur_level);
 412 
 413   // If OSR method level is greater than the regular method level, the levels should be
 414   // equalized by raising the regular method level in order to avoid OSRs during each
 415   // invocation of the method.
 416   if (osr_level == CompLevel_full_optimization && cur_level == CompLevel_full_profile) {
 417     MethodData* mdo = method->method_data();
 418     guarantee(mdo != NULL, "MDO should not be NULL");
 419     if (mdo->invocation_count() >= 1) {
 420       next_level = CompLevel_full_optimization;
 421     }
 422   } else {
 423     next_level = MAX2(osr_level, next_level);
 424   }
 425   return next_level;
 426 }
 427 
 428 // Determine if we should do an OSR compilation of a given method.
 429 CompLevel AdvancedThresholdPolicy::loop_event(Method* method, CompLevel cur_level) {
 430   CompLevel next_level = common(&AdvancedThresholdPolicy::loop_predicate, method, cur_level, true);
 431   if (cur_level == CompLevel_none) {
 432     // If there is a live OSR method that means that we deopted to the interpreter
 433     // for the transition.
 434     CompLevel osr_level = MIN2((CompLevel)method->highest_osr_comp_level(), next_level);
 435     if (osr_level > CompLevel_none) {
 436       return osr_level;
 437     }
 438   }
 439   return next_level;
 440 }
 441 
 442 // Update the rate and submit compile
 443 void AdvancedThresholdPolicy::submit_compile(methodHandle mh, int bci, CompLevel level, JavaThread* thread) {
 444   int hot_count = (bci == InvocationEntryBci) ? mh->invocation_count() : mh->backedge_count();
 445   update_rate(os::javaTimeMillis(), mh());
 446   CompileBroker::compile_method(mh, bci, level, mh, hot_count, "tiered", thread);
 447 }
 448 
 449 // Handle the invocation event.
 450 void AdvancedThresholdPolicy::method_invocation_event(methodHandle mh, methodHandle imh,
 451                                                       CompLevel level, nmethod* nm, JavaThread* thread) {
 452   if (should_create_mdo(mh(), level)) {
 453     create_mdo(mh, thread);
 454   }
 455   if (is_compilation_enabled() && !CompileBroker::compilation_is_in_queue(mh, InvocationEntryBci)) {
 456     CompLevel next_level = call_event(mh(), level);
 457     if (next_level != level) {
 458       compile(mh, InvocationEntryBci, next_level, thread);
 459     }
 460   }
 461 }
 462 
 463 // Handle the back branch event. Notice that we can compile the method
 464 // with a regular entry from here.
 465 void AdvancedThresholdPolicy::method_back_branch_event(methodHandle mh, methodHandle imh,
 466                                                        int bci, CompLevel level, nmethod* nm, JavaThread* thread) {
 467   if (should_create_mdo(mh(), level)) {
 468     create_mdo(mh, thread);
 469   }
 470   // Check if MDO should be created for the inlined method
 471   if (should_create_mdo(imh(), level)) {
 472     create_mdo(imh, thread);
 473   }
 474 
 475   if (is_compilation_enabled()) {
 476     CompLevel next_osr_level = loop_event(imh(), level);
 477     CompLevel max_osr_level = (CompLevel)imh->highest_osr_comp_level();
 478     // At the very least compile the OSR version
 479     if (!CompileBroker::compilation_is_in_queue(imh, bci) && next_osr_level != level) {
 480       compile(imh, bci, next_osr_level, thread);
 481     }
 482 
 483     // Use loop event as an opportunity to also check if there's been
 484     // enough calls.
 485     CompLevel cur_level, next_level;
 486     if (mh() != imh()) { // If there is an enclosing method
 487       guarantee(nm != NULL, "Should have nmethod here");
 488       cur_level = comp_level(mh());
 489       next_level = call_event(mh(), cur_level);
 490 
 491       if (max_osr_level == CompLevel_full_optimization) {
 492         // The inlinee OSRed to full opt, we need to modify the enclosing method to avoid deopts
 493         bool make_not_entrant = false;
 494         if (nm->is_osr_method()) {
 495           // This is an osr method, just make it not entrant and recompile later if needed
 496           make_not_entrant = true;
 497         } else {
 498           if (next_level != CompLevel_full_optimization) {
 499             // next_level is not full opt, so we need to recompile the
 500             // enclosing method without the inlinee
 501             cur_level = CompLevel_none;
 502             make_not_entrant = true;
 503           }
 504         }
 505         if (make_not_entrant) {
 506           if (PrintTieredEvents) {
 507             int osr_bci = nm->is_osr_method() ? nm->osr_entry_bci() : InvocationEntryBci;
 508             print_event(MAKE_NOT_ENTRANT, mh(), mh(), osr_bci, level);
 509           }
 510           nm->make_not_entrant();
 511         }
 512       }
 513       if (!CompileBroker::compilation_is_in_queue(mh, InvocationEntryBci)) {
 514         // Fix up next_level if necessary to avoid deopts
 515         if (next_level == CompLevel_limited_profile && max_osr_level == CompLevel_full_profile) {
 516           next_level = CompLevel_full_profile;
 517         }
 518         if (cur_level != next_level) {
 519           compile(mh, InvocationEntryBci, next_level, thread);
 520         }
 521       }
 522     } else {
 523       cur_level = comp_level(imh());
 524       next_level = call_event(imh(), cur_level);
 525       if (!CompileBroker::compilation_is_in_queue(imh, bci) && next_level != cur_level) {
 526         compile(imh, InvocationEntryBci, next_level, thread);
 527       }
 528     }
 529   }
 530 }
 531 
 532 #endif // TIERED