Fri, 31 Oct 2014 12:16:20 +0100
8062169: Multiple OSR compilations issued for same bci
Summary: Fixed 'SimpleThresholdPolicy::event' to always perform OSR if an OSR nmethod is available.
Reviewed-by: kvn, iveresov
1 /*
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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5 * This code is free software; you can redistribute it and/or modify it
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13 * accompanied this code).
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23 */
25 #include "precompiled.hpp"
26 #include "runtime/advancedThresholdPolicy.hpp"
27 #include "runtime/simpleThresholdPolicy.inline.hpp"
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());
37 tty->print(" k=%.2lf,%.2lf", threshold_scale(CompLevel_full_profile, Tier3LoadFeedback),
38 threshold_scale(CompLevel_full_optimization, Tier4LoadFeedback));
40 }
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 }
55 set_c1_count(MAX2(count / 3, 1));
56 set_c2_count(MAX2(count - c1_count(), 1));
57 FLAG_SET_ERGO(intx, CICompilerCount, c1_count() + c2_count());
59 // Some inlining tuning
60 #ifdef X86
61 if (FLAG_IS_DEFAULT(InlineSmallCode)) {
62 FLAG_SET_DEFAULT(InlineSmallCode, 2000);
63 }
64 #endif
66 #ifdef SPARC
67 if (FLAG_IS_DEFAULT(InlineSmallCode)) {
68 FLAG_SET_DEFAULT(InlineSmallCode, 2500);
69 }
70 #endif
72 set_increase_threshold_at_ratio();
73 set_start_time(os::javaTimeMillis());
74 }
76 // update_rate() is called from select_task() while holding a compile queue lock.
77 void AdvancedThresholdPolicy::update_rate(jlong t, Method* m) {
78 // Skip update if counters are absent.
79 // Can't allocate them since we are holding compile queue lock.
80 if (m->method_counters() == NULL) return;
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);
86 return;
87 }
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();
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);
102 m->set_prev_event_count(event_count);
103 m->set_rate((float)delta_e / (float)delta_t); // 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);
108 }
109 }
110 }
111 }
113 // Check if this method has been stale from a given number of milliseconds.
114 // See select_task().
115 bool AdvancedThresholdPolicy::is_stale(jlong t, jlong timeout, Method* m) {
116 jlong delta_s = t - SafepointSynchronize::end_of_last_safepoint();
117 jlong delta_t = t - m->prev_time();
118 if (delta_t > timeout && delta_s > timeout) {
119 int event_count = m->invocation_count() + m->backedge_count();
120 int delta_e = event_count - m->prev_event_count();
121 // Return true if there were no events.
122 return delta_e == 0;
123 }
124 return false;
125 }
127 // We don't remove old methods from the compile queue even if they have
128 // very low activity. See select_task().
129 bool AdvancedThresholdPolicy::is_old(Method* method) {
130 return method->invocation_count() > 50000 || method->backedge_count() > 500000;
131 }
133 double AdvancedThresholdPolicy::weight(Method* method) {
134 return (method->rate() + 1) * ((method->invocation_count() + 1) * (method->backedge_count() + 1));
135 }
137 // Apply heuristics and return true if x should be compiled before y
138 bool AdvancedThresholdPolicy::compare_methods(Method* x, Method* y) {
139 if (x->highest_comp_level() > y->highest_comp_level()) {
140 // recompilation after deopt
141 return true;
142 } else
143 if (x->highest_comp_level() == y->highest_comp_level()) {
144 if (weight(x) > weight(y)) {
145 return true;
146 }
147 }
148 return false;
149 }
151 // Is method profiled enough?
152 bool AdvancedThresholdPolicy::is_method_profiled(Method* method) {
153 MethodData* mdo = method->method_data();
154 if (mdo != NULL) {
155 int i = mdo->invocation_count_delta();
156 int b = mdo->backedge_count_delta();
157 return call_predicate_helper<CompLevel_full_profile>(i, b, 1);
158 }
159 return false;
160 }
162 // Called with the queue locked and with at least one element
163 CompileTask* AdvancedThresholdPolicy::select_task(CompileQueue* compile_queue) {
164 CompileTask *max_task = NULL;
165 Method* max_method = NULL;
166 jlong t = os::javaTimeMillis();
167 // Iterate through the queue and find a method with a maximum rate.
168 for (CompileTask* task = compile_queue->first(); task != NULL;) {
169 CompileTask* next_task = task->next();
170 Method* method = task->method();
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 compile_queue->remove_and_mark_stale(task);
182 method->clear_queued_for_compilation();
183 task = next_task;
184 continue;
185 }
187 // Select a method with a higher rate
188 if (compare_methods(method, max_method)) {
189 max_task = task;
190 max_method = method;
191 }
192 }
193 task = next_task;
194 }
196 if (max_task->comp_level() == CompLevel_full_profile && TieredStopAtLevel > CompLevel_full_profile
197 && is_method_profiled(max_method)) {
198 max_task->set_comp_level(CompLevel_limited_profile);
199 if (PrintTieredEvents) {
200 print_event(UPDATE_IN_QUEUE, max_method, max_method, max_task->osr_bci(), (CompLevel)max_task->comp_level());
201 }
202 }
204 return max_task;
205 }
207 double AdvancedThresholdPolicy::threshold_scale(CompLevel level, int feedback_k) {
208 double queue_size = CompileBroker::queue_size(level);
209 int comp_count = compiler_count(level);
210 double k = queue_size / (feedback_k * comp_count) + 1;
212 // Increase C1 compile threshold when the code cache is filled more
213 // than specified by IncreaseFirstTierCompileThresholdAt percentage.
214 // The main intention is to keep enough free space for C2 compiled code
215 // to achieve peak performance if the code cache is under stress.
216 if ((TieredStopAtLevel == CompLevel_full_optimization) && (level != CompLevel_full_optimization)) {
217 double current_reverse_free_ratio = CodeCache::reverse_free_ratio();
218 if (current_reverse_free_ratio > _increase_threshold_at_ratio) {
219 k *= exp(current_reverse_free_ratio - _increase_threshold_at_ratio);
220 }
221 }
222 return k;
223 }
225 // Call and loop predicates determine whether a transition to a higher
226 // compilation level should be performed (pointers to predicate functions
227 // are passed to common()).
228 // Tier?LoadFeedback is basically a coefficient that determines of
229 // how many methods per compiler thread can be in the queue before
230 // the threshold values double.
231 bool AdvancedThresholdPolicy::loop_predicate(int i, int b, CompLevel cur_level) {
232 switch(cur_level) {
233 case CompLevel_none:
234 case CompLevel_limited_profile: {
235 double k = threshold_scale(CompLevel_full_profile, Tier3LoadFeedback);
236 return loop_predicate_helper<CompLevel_none>(i, b, k);
237 }
238 case CompLevel_full_profile: {
239 double k = threshold_scale(CompLevel_full_optimization, Tier4LoadFeedback);
240 return loop_predicate_helper<CompLevel_full_profile>(i, b, k);
241 }
242 default:
243 return true;
244 }
245 }
247 bool AdvancedThresholdPolicy::call_predicate(int i, int b, CompLevel cur_level) {
248 switch(cur_level) {
249 case CompLevel_none:
250 case CompLevel_limited_profile: {
251 double k = threshold_scale(CompLevel_full_profile, Tier3LoadFeedback);
252 return call_predicate_helper<CompLevel_none>(i, b, k);
253 }
254 case CompLevel_full_profile: {
255 double k = threshold_scale(CompLevel_full_optimization, Tier4LoadFeedback);
256 return call_predicate_helper<CompLevel_full_profile>(i, b, k);
257 }
258 default:
259 return true;
260 }
261 }
263 // If a method is old enough and is still in the interpreter we would want to
264 // start profiling without waiting for the compiled method to arrive.
265 // We also take the load on compilers into the account.
266 bool AdvancedThresholdPolicy::should_create_mdo(Method* method, CompLevel cur_level) {
267 if (cur_level == CompLevel_none &&
268 CompileBroker::queue_size(CompLevel_full_optimization) <=
269 Tier3DelayOn * compiler_count(CompLevel_full_optimization)) {
270 int i = method->invocation_count();
271 int b = method->backedge_count();
272 double k = Tier0ProfilingStartPercentage / 100.0;
273 return call_predicate_helper<CompLevel_none>(i, b, k) || loop_predicate_helper<CompLevel_none>(i, b, k);
274 }
275 return false;
276 }
278 // Inlining control: if we're compiling a profiled method with C1 and the callee
279 // is known to have OSRed in a C2 version, don't inline it.
280 bool AdvancedThresholdPolicy::should_not_inline(ciEnv* env, ciMethod* callee) {
281 CompLevel comp_level = (CompLevel)env->comp_level();
282 if (comp_level == CompLevel_full_profile ||
283 comp_level == CompLevel_limited_profile) {
284 return callee->highest_osr_comp_level() == CompLevel_full_optimization;
285 }
286 return false;
287 }
289 // Create MDO if necessary.
290 void AdvancedThresholdPolicy::create_mdo(methodHandle mh, JavaThread* THREAD) {
291 if (mh->is_native() || mh->is_abstract() || mh->is_accessor()) return;
292 if (mh->method_data() == NULL) {
293 Method::build_interpreter_method_data(mh, CHECK_AND_CLEAR);
294 }
295 }
298 /*
299 * Method states:
300 * 0 - interpreter (CompLevel_none)
301 * 1 - pure C1 (CompLevel_simple)
302 * 2 - C1 with invocation and backedge counting (CompLevel_limited_profile)
303 * 3 - C1 with full profiling (CompLevel_full_profile)
304 * 4 - C2 (CompLevel_full_optimization)
305 *
306 * Common state transition patterns:
307 * a. 0 -> 3 -> 4.
308 * The most common path. But note that even in this straightforward case
309 * profiling can start at level 0 and finish at level 3.
310 *
311 * b. 0 -> 2 -> 3 -> 4.
312 * This case occures when the load on C2 is deemed too high. So, instead of transitioning
313 * into state 3 directly and over-profiling while a method is in the C2 queue we transition to
314 * level 2 and wait until the load on C2 decreases. This path is disabled for OSRs.
315 *
316 * c. 0 -> (3->2) -> 4.
317 * In this case we enqueue a method for compilation at level 3, but the C1 queue is long enough
318 * to enable the profiling to fully occur at level 0. In this case we change the compilation level
319 * of the method to 2, because it'll allow it to run much faster without full profiling while c2
320 * is compiling.
321 *
322 * d. 0 -> 3 -> 1 or 0 -> 2 -> 1.
323 * After a method was once compiled with C1 it can be identified as trivial and be compiled to
324 * level 1. These transition can also occur if a method can't be compiled with C2 but can with C1.
325 *
326 * e. 0 -> 4.
327 * This can happen if a method fails C1 compilation (it will still be profiled in the interpreter)
328 * or because of a deopt that didn't require reprofiling (compilation won't happen in this case because
329 * the compiled version already exists).
330 *
331 * Note that since state 0 can be reached from any other state via deoptimization different loops
332 * are possible.
333 *
334 */
336 // Common transition function. Given a predicate determines if a method should transition to another level.
337 CompLevel AdvancedThresholdPolicy::common(Predicate p, Method* method, CompLevel cur_level, bool disable_feedback) {
338 CompLevel next_level = cur_level;
339 int i = method->invocation_count();
340 int b = method->backedge_count();
342 if (is_trivial(method)) {
343 next_level = CompLevel_simple;
344 } else {
345 switch(cur_level) {
346 case CompLevel_none:
347 // If we were at full profile level, would we switch to full opt?
348 if (common(p, method, CompLevel_full_profile, disable_feedback) == CompLevel_full_optimization) {
349 next_level = CompLevel_full_optimization;
350 } else if ((this->*p)(i, b, cur_level)) {
351 // C1-generated fully profiled code is about 30% slower than the limited profile
352 // code that has only invocation and backedge counters. The observation is that
353 // if C2 queue is large enough we can spend too much time in the fully profiled code
354 // while waiting for C2 to pick the method from the queue. To alleviate this problem
355 // we introduce a feedback on the C2 queue size. If the C2 queue is sufficiently long
356 // we choose to compile a limited profiled version and then recompile with full profiling
357 // when the load on C2 goes down.
358 if (!disable_feedback && CompileBroker::queue_size(CompLevel_full_optimization) >
359 Tier3DelayOn * compiler_count(CompLevel_full_optimization)) {
360 next_level = CompLevel_limited_profile;
361 } else {
362 next_level = CompLevel_full_profile;
363 }
364 }
365 break;
366 case CompLevel_limited_profile:
367 if (is_method_profiled(method)) {
368 // Special case: we got here because this method was fully profiled in the interpreter.
369 next_level = CompLevel_full_optimization;
370 } else {
371 MethodData* mdo = method->method_data();
372 if (mdo != NULL) {
373 if (mdo->would_profile()) {
374 if (disable_feedback || (CompileBroker::queue_size(CompLevel_full_optimization) <=
375 Tier3DelayOff * compiler_count(CompLevel_full_optimization) &&
376 (this->*p)(i, b, cur_level))) {
377 next_level = CompLevel_full_profile;
378 }
379 } else {
380 next_level = CompLevel_full_optimization;
381 }
382 }
383 }
384 break;
385 case CompLevel_full_profile:
386 {
387 MethodData* mdo = method->method_data();
388 if (mdo != NULL) {
389 if (mdo->would_profile()) {
390 int mdo_i = mdo->invocation_count_delta();
391 int mdo_b = mdo->backedge_count_delta();
392 if ((this->*p)(mdo_i, mdo_b, cur_level)) {
393 next_level = CompLevel_full_optimization;
394 }
395 } else {
396 next_level = CompLevel_full_optimization;
397 }
398 }
399 }
400 break;
401 }
402 }
403 return MIN2(next_level, (CompLevel)TieredStopAtLevel);
404 }
406 // Determine if a method should be compiled with a normal entry point at a different level.
407 CompLevel AdvancedThresholdPolicy::call_event(Method* method, CompLevel cur_level) {
408 CompLevel osr_level = MIN2((CompLevel) method->highest_osr_comp_level(),
409 common(&AdvancedThresholdPolicy::loop_predicate, method, cur_level, true));
410 CompLevel next_level = common(&AdvancedThresholdPolicy::call_predicate, method, cur_level);
412 // If OSR method level is greater than the regular method level, the levels should be
413 // equalized by raising the regular method level in order to avoid OSRs during each
414 // invocation of the method.
415 if (osr_level == CompLevel_full_optimization && cur_level == CompLevel_full_profile) {
416 MethodData* mdo = method->method_data();
417 guarantee(mdo != NULL, "MDO should not be NULL");
418 if (mdo->invocation_count() >= 1) {
419 next_level = CompLevel_full_optimization;
420 }
421 } else {
422 next_level = MAX2(osr_level, next_level);
423 }
424 return next_level;
425 }
427 // Determine if we should do an OSR compilation of a given method.
428 CompLevel AdvancedThresholdPolicy::loop_event(Method* method, CompLevel cur_level) {
429 CompLevel next_level = common(&AdvancedThresholdPolicy::loop_predicate, method, cur_level, true);
430 if (cur_level == CompLevel_none) {
431 // If there is a live OSR method that means that we deopted to the interpreter
432 // for the transition.
433 CompLevel osr_level = MIN2((CompLevel)method->highest_osr_comp_level(), next_level);
434 if (osr_level > CompLevel_none) {
435 return osr_level;
436 }
437 }
438 return next_level;
439 }
441 // Update the rate and submit compile
442 void AdvancedThresholdPolicy::submit_compile(methodHandle mh, int bci, CompLevel level, JavaThread* thread) {
443 int hot_count = (bci == InvocationEntryBci) ? mh->invocation_count() : mh->backedge_count();
444 update_rate(os::javaTimeMillis(), mh());
445 CompileBroker::compile_method(mh, bci, level, mh, hot_count, "tiered", thread);
446 }
448 // Handle the invocation event.
449 void AdvancedThresholdPolicy::method_invocation_event(methodHandle mh, methodHandle imh,
450 CompLevel level, nmethod* nm, JavaThread* thread) {
451 if (should_create_mdo(mh(), level)) {
452 create_mdo(mh, thread);
453 }
454 if (is_compilation_enabled() && !CompileBroker::compilation_is_in_queue(mh)) {
455 CompLevel next_level = call_event(mh(), level);
456 if (next_level != level) {
457 compile(mh, InvocationEntryBci, next_level, thread);
458 }
459 }
460 }
462 // Handle the back branch event. Notice that we can compile the method
463 // with a regular entry from here.
464 void AdvancedThresholdPolicy::method_back_branch_event(methodHandle mh, methodHandle imh,
465 int bci, CompLevel level, nmethod* nm, JavaThread* thread) {
466 if (should_create_mdo(mh(), level)) {
467 create_mdo(mh, thread);
468 }
469 // Check if MDO should be created for the inlined method
470 if (should_create_mdo(imh(), level)) {
471 create_mdo(imh, thread);
472 }
474 if (is_compilation_enabled()) {
475 CompLevel next_osr_level = loop_event(imh(), level);
476 CompLevel max_osr_level = (CompLevel)imh->highest_osr_comp_level();
477 // At the very least compile the OSR version
478 if (!CompileBroker::compilation_is_in_queue(imh) && (next_osr_level != level)) {
479 compile(imh, bci, next_osr_level, thread);
480 }
482 // Use loop event as an opportunity to also check if there's been
483 // enough calls.
484 CompLevel cur_level, next_level;
485 if (mh() != imh()) { // If there is an enclosing method
486 guarantee(nm != NULL, "Should have nmethod here");
487 cur_level = comp_level(mh());
488 next_level = call_event(mh(), cur_level);
490 if (max_osr_level == CompLevel_full_optimization) {
491 // The inlinee OSRed to full opt, we need to modify the enclosing method to avoid deopts
492 bool make_not_entrant = false;
493 if (nm->is_osr_method()) {
494 // This is an osr method, just make it not entrant and recompile later if needed
495 make_not_entrant = true;
496 } else {
497 if (next_level != CompLevel_full_optimization) {
498 // next_level is not full opt, so we need to recompile the
499 // enclosing method without the inlinee
500 cur_level = CompLevel_none;
501 make_not_entrant = true;
502 }
503 }
504 if (make_not_entrant) {
505 if (PrintTieredEvents) {
506 int osr_bci = nm->is_osr_method() ? nm->osr_entry_bci() : InvocationEntryBci;
507 print_event(MAKE_NOT_ENTRANT, mh(), mh(), osr_bci, level);
508 }
509 nm->make_not_entrant();
510 }
511 }
512 if (!CompileBroker::compilation_is_in_queue(mh)) {
513 // Fix up next_level if necessary to avoid deopts
514 if (next_level == CompLevel_limited_profile && max_osr_level == CompLevel_full_profile) {
515 next_level = CompLevel_full_profile;
516 }
517 if (cur_level != next_level) {
518 compile(mh, InvocationEntryBci, next_level, thread);
519 }
520 }
521 } else {
522 cur_level = comp_level(imh());
523 next_level = call_event(imh(), cur_level);
524 if (!CompileBroker::compilation_is_in_queue(imh) && (next_level != cur_level)) {
525 compile(imh, InvocationEntryBci, next_level, thread);
526 }
527 }
528 }
529 }
531 #endif // TIERED