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annotate src/share/vm/runtime/advancedThresholdPolicy.hpp @ 14714:b602356a9cfc
additional canonicalizers for accesses and value nodes (improves number of implicit null checks)
author | Lukas Stadler <lukas.stadler@oracle.com> |
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date | Thu, 20 Mar 2014 17:15:36 +0100 |
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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 |