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annotate src/share/vm/runtime/advancedThresholdPolicy.hpp @ 18096:ca6d25be853b jdk8u25-b13
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| author | jiangli |
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| date | Tue, 12 Aug 2014 17:46:16 -0400 |
| parents | 55fb97c4c58d |
| children | 4ca6dc0799b6 |
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| 2348 | 1 /* |
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2 * Copyright (c) 2010, 2013, Oracle and/or its affiliates. All rights reserved. |
| 3358 | 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 */ | |
| 2348 | 24 |
| 25 #ifndef SHARE_VM_RUNTIME_ADVANCEDTHRESHOLDPOLICY_HPP | |
| 26 #define SHARE_VM_RUNTIME_ADVANCEDTHRESHOLDPOLICY_HPP | |
| 27 | |
| 28 #include "runtime/simpleThresholdPolicy.hpp" | |
| 29 | |
| 30 #ifdef TIERED | |
| 31 class CompileTask; | |
| 32 class CompileQueue; | |
| 33 | |
| 34 /* | |
| 35 * The system supports 5 execution levels: | |
| 36 * * level 0 - interpreter | |
| 37 * * level 1 - C1 with full optimization (no profiling) | |
| 38 * * level 2 - C1 with invocation and backedge counters | |
| 39 * * level 3 - C1 with full profiling (level 2 + MDO) | |
| 40 * * level 4 - C2 | |
| 41 * | |
| 42 * Levels 0, 2 and 3 periodically notify the runtime about the current value of the counters | |
| 43 * (invocation counters and backedge counters). The frequency of these notifications is | |
| 44 * different at each level. These notifications are used by the policy to decide what transition | |
| 45 * to make. | |
| 46 * | |
| 47 * Execution starts at level 0 (interpreter), then the policy can decide either to compile the | |
| 48 * method at level 3 or level 2. The decision is based on the following factors: | |
| 49 * 1. The length of the C2 queue determines the next level. The observation is that level 2 | |
| 50 * is generally faster than level 3 by about 30%, therefore we would want to minimize the time | |
| 51 * a method spends at level 3. We should only spend the time at level 3 that is necessary to get | |
| 52 * adequate profiling. So, if the C2 queue is long enough it is more beneficial to go first to | |
| 53 * level 2, because if we transitioned to level 3 we would be stuck there until our C2 compile | |
| 54 * request makes its way through the long queue. When the load on C2 recedes we are going to | |
| 55 * recompile at level 3 and start gathering profiling information. | |
| 56 * 2. The length of C1 queue is used to dynamically adjust the thresholds, so as to introduce | |
| 57 * additional filtering if the compiler is overloaded. The rationale is that by the time a | |
| 58 * method gets compiled it can become unused, so it doesn't make sense to put too much onto the | |
| 59 * queue. | |
| 60 * | |
| 61 * After profiling is completed at level 3 the transition is made to level 4. Again, the length | |
| 62 * of the C2 queue is used as a feedback to adjust the thresholds. | |
| 63 * | |
| 64 * After the first C1 compile some basic information is determined about the code like the number | |
| 65 * of the blocks and the number of the loops. Based on that it can be decided that a method | |
| 66 * is trivial and compiling it with C1 will yield the same code. In this case the method is | |
| 67 * compiled at level 1 instead of 4. | |
| 68 * | |
| 69 * We also support profiling at level 0. If C1 is slow enough to produce the level 3 version of | |
| 70 * the code and the C2 queue is sufficiently small we can decide to start profiling in the | |
| 71 * interpreter (and continue profiling in the compiled code once the level 3 version arrives). | |
| 72 * If the profiling at level 0 is fully completed before level 3 version is produced, a level 2 | |
| 73 * version is compiled instead in order to run faster waiting for a level 4 version. | |
| 74 * | |
| 75 * Compile queues are implemented as priority queues - for each method in the queue we compute | |
| 76 * the event rate (the number of invocation and backedge counter increments per unit of time). | |
| 77 * When getting an element off the queue we pick the one with the largest rate. Maintaining the | |
| 78 * rate also allows us to remove stale methods (the ones that got on the queue but stopped | |
| 79 * being used shortly after that). | |
| 80 */ | |
| 81 | |
| 82 /* Command line options: | |
| 83 * - Tier?InvokeNotifyFreqLog and Tier?BackedgeNotifyFreqLog control the frequency of method | |
| 84 * invocation and backedge notifications. Basically every n-th invocation or backedge a mutator thread | |
| 85 * makes a call into the runtime. | |
| 86 * | |
| 87 * - Tier?CompileThreshold, Tier?BackEdgeThreshold, Tier?MinInvocationThreshold control | |
| 88 * compilation thresholds. | |
| 89 * Level 2 thresholds are not used and are provided for option-compatibility and potential future use. | |
| 90 * Other thresholds work as follows: | |
| 91 * | |
| 92 * Transition from interpreter (level 0) to C1 with full profiling (level 3) happens when | |
| 93 * the following predicate is true (X is the level): | |
| 94 * | |
| 95 * i > TierXInvocationThreshold * s || (i > TierXMinInvocationThreshold * s && i + b > TierXCompileThreshold * s), | |
| 96 * | |
| 97 * where $i$ is the number of method invocations, $b$ number of backedges and $s$ is the scaling | |
| 98 * coefficient that will be discussed further. | |
| 99 * The intuition is to equalize the time that is spend profiling each method. | |
| 100 * The same predicate is used to control the transition from level 3 to level 4 (C2). It should be | |
| 101 * noted though that the thresholds are relative. Moreover i and b for the 0->3 transition come | |
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102 * from Method* and for 3->4 transition they come from MDO (since profiled invocations are |
| 2348 | 103 * counted separately). |
| 104 * | |
| 105 * OSR transitions are controlled simply with b > TierXBackEdgeThreshold * s predicates. | |
| 106 * | |
| 107 * - Tier?LoadFeedback options are used to automatically scale the predicates described above depending | |
| 108 * on the compiler load. The scaling coefficients are computed as follows: | |
| 109 * | |
| 110 * s = queue_size_X / (TierXLoadFeedback * compiler_count_X) + 1, | |
| 111 * | |
| 112 * where queue_size_X is the current size of the compiler queue of level X, and compiler_count_X | |
| 113 * is the number of level X compiler threads. | |
| 114 * | |
| 115 * Basically these parameters describe how many methods should be in the compile queue | |
| 116 * per compiler thread before the scaling coefficient increases by one. | |
| 117 * | |
| 118 * This feedback provides the mechanism to automatically control the flow of compilation requests | |
| 119 * depending on the machine speed, mutator load and other external factors. | |
| 120 * | |
| 121 * - Tier3DelayOn and Tier3DelayOff parameters control another important feedback loop. | |
| 122 * Consider the following observation: a method compiled with full profiling (level 3) | |
| 123 * is about 30% slower than a method at level 2 (just invocation and backedge counters, no MDO). | |
| 124 * Normally, the following transitions will occur: 0->3->4. The problem arises when the C2 queue | |
| 125 * gets congested and the 3->4 transition is delayed. While the method is the C2 queue it continues | |
| 126 * executing at level 3 for much longer time than is required by the predicate and at suboptimal speed. | |
| 127 * The idea is to dynamically change the behavior of the system in such a way that if a substantial | |
| 128 * load on C2 is detected we would first do the 0->2 transition allowing a method to run faster. | |
| 129 * And then when the load decreases to allow 2->3 transitions. | |
| 130 * | |
| 131 * Tier3Delay* parameters control this switching mechanism. | |
| 132 * Tier3DelayOn is the number of methods in the C2 queue per compiler thread after which the policy | |
| 133 * no longer does 0->3 transitions but does 0->2 transitions instead. | |
| 134 * Tier3DelayOff switches the original behavior back when the number of methods in the C2 queue | |
| 135 * per compiler thread falls below the specified amount. | |
| 136 * The hysteresis is necessary to avoid jitter. | |
| 137 * | |
| 138 * - TieredCompileTaskTimeout is the amount of time an idle method can spend in the compile queue. | |
| 139 * Basically, since we use the event rate d(i + b)/dt as a value of priority when selecting a method to | |
| 140 * compile from the compile queue, we also can detect stale methods for which the rate has been | |
| 141 * 0 for some time in the same iteration. Stale methods can appear in the queue when an application | |
| 142 * abruptly changes its behavior. | |
| 143 * | |
| 144 * - TieredStopAtLevel, is used mostly for testing. It allows to bypass the policy logic and stick | |
| 145 * to a given level. For example it's useful to set TieredStopAtLevel = 1 in order to compile everything | |
| 146 * with pure c1. | |
| 147 * | |
| 148 * - Tier0ProfilingStartPercentage allows the interpreter to start profiling when the inequalities in the | |
| 149 * 0->3 predicate are already exceeded by the given percentage but the level 3 version of the | |
| 150 * method is still not ready. We can even go directly from level 0 to 4 if c1 doesn't produce a compiled | |
| 151 * version in time. This reduces the overall transition to level 4 and decreases the startup time. | |
| 152 * Note that this behavior is also guarded by the Tier3Delay mechanism: when the c2 queue is too long | |
| 153 * these is not reason to start profiling prematurely. | |
| 154 * | |
| 155 * - TieredRateUpdateMinTime and TieredRateUpdateMaxTime are parameters of the rate computation. | |
| 156 * Basically, the rate is not computed more frequently than TieredRateUpdateMinTime and is considered | |
| 157 * to be zero if no events occurred in TieredRateUpdateMaxTime. | |
| 158 */ | |
| 159 | |
| 160 | |
| 161 class AdvancedThresholdPolicy : public SimpleThresholdPolicy { | |
| 162 jlong _start_time; | |
| 163 | |
| 164 // Call and loop predicates determine whether a transition to a higher compilation | |
| 165 // level should be performed (pointers to predicate functions are passed to common(). | |
| 166 // Predicates also take compiler load into account. | |
| 167 typedef bool (AdvancedThresholdPolicy::*Predicate)(int i, int b, CompLevel cur_level); | |
| 168 bool call_predicate(int i, int b, CompLevel cur_level); | |
| 169 bool loop_predicate(int i, int b, CompLevel cur_level); | |
| 170 // Common transition function. Given a predicate determines if a method should transition to another level. | |
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171 CompLevel common(Predicate p, Method* method, CompLevel cur_level, bool disable_feedback = false); |
| 2348 | 172 // Transition functions. |
| 173 // call_event determines if a method should be compiled at a different | |
| 174 // level with a regular invocation entry. | |
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175 CompLevel call_event(Method* method, CompLevel cur_level); |
| 2348 | 176 // loop_event checks if a method should be OSR compiled at a different |
| 177 // level. | |
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178 CompLevel loop_event(Method* method, CompLevel cur_level); |
| 2348 | 179 // Has a method been long around? |
| 180 // We don't remove old methods from the compile queue even if they have | |
| 181 // very low activity (see select_task()). | |
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182 inline bool is_old(Method* method); |
| 2348 | 183 // Was a given method inactive for a given number of milliseconds. |
| 184 // If it is, we would remove it from the queue (see select_task()). | |
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185 inline bool is_stale(jlong t, jlong timeout, Method* m); |
| 2348 | 186 // Compute the weight of the method for the compilation scheduling |
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187 inline double weight(Method* method); |
| 2348 | 188 // Apply heuristics and return true if x should be compiled before y |
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189 inline bool compare_methods(Method* x, Method* y); |
| 2348 | 190 // Compute event rate for a given method. The rate is the number of event (invocations + backedges) |
| 191 // per millisecond. | |
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192 inline void update_rate(jlong t, Method* m); |
| 2348 | 193 // Compute threshold scaling coefficient |
| 194 inline double threshold_scale(CompLevel level, int feedback_k); | |
| 195 // If a method is old enough and is still in the interpreter we would want to | |
| 196 // start profiling without waiting for the compiled method to arrive. This function | |
| 197 // determines whether we should do that. | |
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198 inline bool should_create_mdo(Method* method, CompLevel cur_level); |
| 2348 | 199 // Create MDO if necessary. |
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200 void create_mdo(methodHandle mh, JavaThread* thread); |
| 2348 | 201 // Is method profiled enough? |
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202 bool is_method_profiled(Method* method); |
| 2348 | 203 |
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204 double _increase_threshold_at_ratio; |
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205 |
| 2348 | 206 protected: |
| 207 void print_specific(EventType type, methodHandle mh, methodHandle imh, int bci, CompLevel level); | |
| 208 | |
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209 void set_increase_threshold_at_ratio() { _increase_threshold_at_ratio = 100 / (100 - (double)IncreaseFirstTierCompileThresholdAt); } |
| 2348 | 210 void set_start_time(jlong t) { _start_time = t; } |
| 211 jlong start_time() const { return _start_time; } | |
| 212 | |
| 213 // Submit a given method for compilation (and update the rate). | |
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214 virtual void submit_compile(methodHandle mh, int bci, CompLevel level, JavaThread* thread); |
| 2348 | 215 // event() from SimpleThresholdPolicy would call these. |
| 216 virtual void method_invocation_event(methodHandle method, methodHandle inlinee, | |
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217 CompLevel level, nmethod* nm, JavaThread* thread); |
| 2348 | 218 virtual void method_back_branch_event(methodHandle method, methodHandle inlinee, |
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219 int bci, CompLevel level, nmethod* nm, JavaThread* thread); |
| 2348 | 220 public: |
| 221 AdvancedThresholdPolicy() : _start_time(0) { } | |
| 222 // Select task is called by CompileBroker. We should return a task or NULL. | |
| 223 virtual CompileTask* select_task(CompileQueue* compile_queue); | |
| 224 virtual void initialize(); | |
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225 virtual bool should_not_inline(ciEnv* env, ciMethod* callee); |
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226 |
| 2348 | 227 }; |
| 228 | |
| 229 #endif // TIERED | |
| 230 | |
| 231 #endif // SHARE_VM_RUNTIME_ADVANCEDTHRESHOLDPOLICY_HPP |