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 #ifndef SHARE_VM_RUNTIME_SIMPLETHRESHOLDPOLICY_HPP
26 #define SHARE_VM_RUNTIME_SIMPLETHRESHOLDPOLICY_HPP
27
28 #include "code/nmethod.hpp"
29 #include "oops/methodData.hpp"
30 #include "runtime/compilationPolicy.hpp"
31 #include "utilities/globalDefinitions.hpp"
32
33 #ifdef TIERED
34
35 class CompileTask;
36 class CompileQueue;
37
38 class SimpleThresholdPolicy : public CompilationPolicy {
39 int _c1_count, _c2_count;
40
41 // Check if the counter is big enough and set carry (effectively infinity).
42 inline void set_carry_if_necessary(InvocationCounter *counter);
43 // Set carry flags in the counters (in Method* and MDO).
44 inline void handle_counter_overflow(Method* method);
45 // Call and loop predicates determine whether a transition to a higher compilation
46 // level should be performed (pointers to predicate functions are passed to common_TF().
47 // Predicates also take compiler load into account.
48 typedef bool (SimpleThresholdPolicy::*Predicate)(int i, int b, CompLevel cur_level, Method* method);
49 bool call_predicate(int i, int b, CompLevel cur_level, Method* method);
50 bool loop_predicate(int i, int b, CompLevel cur_level, Method* method);
51 // Common transition function. Given a predicate determines if a method should transition to another level.
52 CompLevel common(Predicate p, Method* method, CompLevel cur_level);
53 // Transition functions.
54 // call_event determines if a method should be compiled at a different
55 // level with a regular invocation entry.
56 CompLevel call_event(Method* method, CompLevel cur_level, JavaThread* thread);
57 // loop_event checks if a method should be OSR compiled at a different
58 // level.
59 CompLevel loop_event(Method* method, CompLevel cur_level, JavaThread* thread);
60 void print_counters(const char* prefix, const methodHandle& mh);
61 protected:
62 int c1_count() const { return _c1_count; }
63 int c2_count() const { return _c2_count; }
64 void set_c1_count(int x) { _c1_count = x; }
65 void set_c2_count(int x) { _c2_count = x; }
66
67 enum EventType { CALL, LOOP, COMPILE, REMOVE_FROM_QUEUE, UPDATE_IN_QUEUE, REPROFILE, MAKE_NOT_ENTRANT };
68 void print_event(EventType type, const methodHandle& mh, const methodHandle& imh, int bci, CompLevel level);
69 // Print policy-specific information if necessary
70 virtual void print_specific(EventType type, const methodHandle& mh, const methodHandle& imh, int bci, CompLevel level) { }
71 // Check if the method can be compiled, change level if necessary
72 void compile(const methodHandle& mh, int bci, CompLevel level, JavaThread* thread);
73 // Submit a given method for compilation
74 virtual void submit_compile(const methodHandle& mh, int bci, CompLevel level, JavaThread* thread);
75 // Simple methods are as good being compiled with C1 as C2.
76 // This function tells if it's such a function.
77 inline bool is_trivial(Method* method);
78
79 // Predicate helpers are used by .*_predicate() methods as well as others.
80 // They check the given counter values, multiplied by the scale against the thresholds.
81 template<CompLevel level> static inline bool call_predicate_helper(int i, int b, double scale, Method* method);
82 template<CompLevel level> static inline bool loop_predicate_helper(int i, int b, double scale, Method* method);
83
84 // Get a compilation level for a given method.
85 static CompLevel comp_level(Method* method);
86 virtual void method_invocation_event(const methodHandle& method, const methodHandle& inlinee,
87 CompLevel level, CompiledMethod* nm, JavaThread* thread);
88 virtual void method_back_branch_event(const methodHandle& method, const methodHandle& inlinee,
89 int bci, CompLevel level, CompiledMethod* nm, JavaThread* thread);
90 public:
91 SimpleThresholdPolicy() : _c1_count(0), _c2_count(0) { }
92 virtual int compiler_count(CompLevel comp_level) {
93 if (is_c1_compile(comp_level)) return c1_count();
94 if (is_c2_compile(comp_level)) return c2_count();
95 return 0;
96 }
97 virtual CompLevel initial_compile_level() { return MIN2((CompLevel)TieredStopAtLevel, CompLevel_initial_compile); }
98 virtual void do_safepoint_work() { }
99 virtual void delay_compilation(Method* method) { }
100 virtual void disable_compilation(Method* method) { }
101 virtual void reprofile(ScopeDesc* trap_scope, bool is_osr);
102 virtual nmethod* event(const methodHandle& method, const methodHandle& inlinee,
103 int branch_bci, int bci, CompLevel comp_level, CompiledMethod* nm, JavaThread* thread);
104 // Select task is called by CompileBroker. We should return a task or NULL.
105 virtual CompileTask* select_task(CompileQueue* compile_queue);
106 // Tell the runtime if we think a given method is adequately profiled.
107 virtual bool is_mature(Method* method);
108 // Initialize: set compiler thread count
109 virtual void initialize();
110 virtual bool should_not_inline(ciEnv* env, ciMethod* callee) {
111 return (env->comp_level() == CompLevel_limited_profile ||
112 env->comp_level() == CompLevel_full_profile) &&
113 callee->has_loops();
114 }
115 };
116
117 #endif // TIERED
118
119 #endif // SHARE_VM_RUNTIME_SIMPLETHRESHOLDPOLICY_HPP
|
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 #ifndef SHARE_VM_RUNTIME_SIMPLETHRESHOLDPOLICY_HPP
26 #define SHARE_VM_RUNTIME_SIMPLETHRESHOLDPOLICY_HPP
27
28 #include "code/nmethod.hpp"
29 #include "oops/methodData.hpp"
30 #include "runtime/compilationPolicy.hpp"
31 #include "utilities/globalDefinitions.hpp"
32
33 #ifdef TIERED
34
35 class CompileTask;
36 class CompileQueue;
37 /*
38 * The system supports 5 execution levels:
39 * * level 0 - interpreter
40 * * level 1 - C1 with full optimization (no profiling)
41 * * level 2 - C1 with invocation and backedge counters
42 * * level 3 - C1 with full profiling (level 2 + MDO)
43 * * level 4 - C2
44 *
45 * Levels 0, 2 and 3 periodically notify the runtime about the current value of the counters
46 * (invocation counters and backedge counters). The frequency of these notifications is
47 * different at each level. These notifications are used by the policy to decide what transition
48 * to make.
49 *
50 * Execution starts at level 0 (interpreter), then the policy can decide either to compile the
51 * method at level 3 or level 2. The decision is based on the following factors:
52 * 1. The length of the C2 queue determines the next level. The observation is that level 2
53 * is generally faster than level 3 by about 30%, therefore we would want to minimize the time
54 * a method spends at level 3. We should only spend the time at level 3 that is necessary to get
55 * adequate profiling. So, if the C2 queue is long enough it is more beneficial to go first to
56 * level 2, because if we transitioned to level 3 we would be stuck there until our C2 compile
57 * request makes its way through the long queue. When the load on C2 recedes we are going to
58 * recompile at level 3 and start gathering profiling information.
59 * 2. The length of C1 queue is used to dynamically adjust the thresholds, so as to introduce
60 * additional filtering if the compiler is overloaded. The rationale is that by the time a
61 * method gets compiled it can become unused, so it doesn't make sense to put too much onto the
62 * queue.
63 *
64 * After profiling is completed at level 3 the transition is made to level 4. Again, the length
65 * of the C2 queue is used as a feedback to adjust the thresholds.
66 *
67 * After the first C1 compile some basic information is determined about the code like the number
68 * of the blocks and the number of the loops. Based on that it can be decided that a method
69 * is trivial and compiling it with C1 will yield the same code. In this case the method is
70 * compiled at level 1 instead of 4.
71 *
72 * We also support profiling at level 0. If C1 is slow enough to produce the level 3 version of
73 * the code and the C2 queue is sufficiently small we can decide to start profiling in the
74 * interpreter (and continue profiling in the compiled code once the level 3 version arrives).
75 * If the profiling at level 0 is fully completed before level 3 version is produced, a level 2
76 * version is compiled instead in order to run faster waiting for a level 4 version.
77 *
78 * Compile queues are implemented as priority queues - for each method in the queue we compute
79 * the event rate (the number of invocation and backedge counter increments per unit of time).
80 * When getting an element off the queue we pick the one with the largest rate. Maintaining the
81 * rate also allows us to remove stale methods (the ones that got on the queue but stopped
82 * being used shortly after that).
83 */
84
85 /* Command line options:
86 * - Tier?InvokeNotifyFreqLog and Tier?BackedgeNotifyFreqLog control the frequency of method
87 * invocation and backedge notifications. Basically every n-th invocation or backedge a mutator thread
88 * makes a call into the runtime.
89 *
90 * - Tier?InvocationThreshold, Tier?CompileThreshold, Tier?BackEdgeThreshold, Tier?MinInvocationThreshold control
91 * compilation thresholds.
92 * Level 2 thresholds are not used and are provided for option-compatibility and potential future use.
93 * Other thresholds work as follows:
94 *
95 * Transition from interpreter (level 0) to C1 with full profiling (level 3) happens when
96 * the following predicate is true (X is the level):
97 *
98 * i > TierXInvocationThreshold * s || (i > TierXMinInvocationThreshold * s && i + b > TierXCompileThreshold * s),
99 *
100 * where $i$ is the number of method invocations, $b$ number of backedges and $s$ is the scaling
101 * coefficient that will be discussed further.
102 * The intuition is to equalize the time that is spend profiling each method.
103 * The same predicate is used to control the transition from level 3 to level 4 (C2). It should be
104 * noted though that the thresholds are relative. Moreover i and b for the 0->3 transition come
105 * from Method* and for 3->4 transition they come from MDO (since profiled invocations are
106 * counted separately). Finally, if a method does not contain anything worth profiling, a transition
107 * from level 3 to level 4 occurs without considering thresholds (e.g., with fewer invocations than
108 * what is specified by Tier4InvocationThreshold).
109 *
110 * OSR transitions are controlled simply with b > TierXBackEdgeThreshold * s predicates.
111 *
112 * - Tier?LoadFeedback options are used to automatically scale the predicates described above depending
113 * on the compiler load. The scaling coefficients are computed as follows:
114 *
115 * s = queue_size_X / (TierXLoadFeedback * compiler_count_X) + 1,
116 *
117 * where queue_size_X is the current size of the compiler queue of level X, and compiler_count_X
118 * is the number of level X compiler threads.
119 *
120 * Basically these parameters describe how many methods should be in the compile queue
121 * per compiler thread before the scaling coefficient increases by one.
122 *
123 * This feedback provides the mechanism to automatically control the flow of compilation requests
124 * depending on the machine speed, mutator load and other external factors.
125 *
126 * - Tier3DelayOn and Tier3DelayOff parameters control another important feedback loop.
127 * Consider the following observation: a method compiled with full profiling (level 3)
128 * is about 30% slower than a method at level 2 (just invocation and backedge counters, no MDO).
129 * Normally, the following transitions will occur: 0->3->4. The problem arises when the C2 queue
130 * gets congested and the 3->4 transition is delayed. While the method is the C2 queue it continues
131 * executing at level 3 for much longer time than is required by the predicate and at suboptimal speed.
132 * The idea is to dynamically change the behavior of the system in such a way that if a substantial
133 * load on C2 is detected we would first do the 0->2 transition allowing a method to run faster.
134 * And then when the load decreases to allow 2->3 transitions.
135 *
136 * Tier3Delay* parameters control this switching mechanism.
137 * Tier3DelayOn is the number of methods in the C2 queue per compiler thread after which the policy
138 * no longer does 0->3 transitions but does 0->2 transitions instead.
139 * Tier3DelayOff switches the original behavior back when the number of methods in the C2 queue
140 * per compiler thread falls below the specified amount.
141 * The hysteresis is necessary to avoid jitter.
142 *
143 * - TieredCompileTaskTimeout is the amount of time an idle method can spend in the compile queue.
144 * Basically, since we use the event rate d(i + b)/dt as a value of priority when selecting a method to
145 * compile from the compile queue, we also can detect stale methods for which the rate has been
146 * 0 for some time in the same iteration. Stale methods can appear in the queue when an application
147 * abruptly changes its behavior.
148 *
149 * - TieredStopAtLevel, is used mostly for testing. It allows to bypass the policy logic and stick
150 * to a given level. For example it's useful to set TieredStopAtLevel = 1 in order to compile everything
151 * with pure c1.
152 *
153 * - Tier0ProfilingStartPercentage allows the interpreter to start profiling when the inequalities in the
154 * 0->3 predicate are already exceeded by the given percentage but the level 3 version of the
155 * method is still not ready. We can even go directly from level 0 to 4 if c1 doesn't produce a compiled
156 * version in time. This reduces the overall transition to level 4 and decreases the startup time.
157 * Note that this behavior is also guarded by the Tier3Delay mechanism: when the c2 queue is too long
158 * these is not reason to start profiling prematurely.
159 *
160 * - TieredRateUpdateMinTime and TieredRateUpdateMaxTime are parameters of the rate computation.
161 * Basically, the rate is not computed more frequently than TieredRateUpdateMinTime and is considered
162 * to be zero if no events occurred in TieredRateUpdateMaxTime.
163 */
164
165 class SimpleThresholdPolicy : public CompilationPolicy {
166 jlong _start_time;
167 int _c1_count, _c2_count;
168
169 // Check if the counter is big enough and set carry (effectively infinity).
170 inline void set_carry_if_necessary(InvocationCounter *counter);
171 // Set carry flags in the counters (in Method* and MDO).
172 inline void handle_counter_overflow(Method* method);
173 // Call and loop predicates determine whether a transition to a higher compilation
174 // level should be performed (pointers to predicate functions are passed to common_TF().
175 // Predicates also take compiler load into account.
176 typedef bool (SimpleThresholdPolicy::*Predicate)(int i, int b, CompLevel cur_level, Method* method);
177 bool call_predicate(int i, int b, CompLevel cur_level, Method* method);
178 bool loop_predicate(int i, int b, CompLevel cur_level, Method* method);
179 // Common transition function. Given a predicate determines if a method should transition to another level.
180 CompLevel common(Predicate p, Method* method, CompLevel cur_level, bool disable_feedback = false);
181 // Transition functions.
182 // call_event determines if a method should be compiled at a different
183 // level with a regular invocation entry.
184 CompLevel call_event(Method* method, CompLevel cur_level, JavaThread* thread);
185 // loop_event checks if a method should be OSR compiled at a different
186 // level.
187 CompLevel loop_event(Method* method, CompLevel cur_level, JavaThread* thread);
188 void print_counters(const char* prefix, const methodHandle& mh);
189 // Has a method been long around?
190 // We don't remove old methods from the compile queue even if they have
191 // very low activity (see select_task()).
192 inline bool is_old(Method* method);
193 // Was a given method inactive for a given number of milliseconds.
194 // If it is, we would remove it from the queue (see select_task()).
195 inline bool is_stale(jlong t, jlong timeout, Method* m);
196 // Compute the weight of the method for the compilation scheduling
197 inline double weight(Method* method);
198 // Apply heuristics and return true if x should be compiled before y
199 inline bool compare_methods(Method* x, Method* y);
200 // Compute event rate for a given method. The rate is the number of event (invocations + backedges)
201 // per millisecond.
202 inline void update_rate(jlong t, Method* m);
203 // Compute threshold scaling coefficient
204 inline double threshold_scale(CompLevel level, int feedback_k);
205 // If a method is old enough and is still in the interpreter we would want to
206 // start profiling without waiting for the compiled method to arrive. This function
207 // determines whether we should do that.
208 inline bool should_create_mdo(Method* method, CompLevel cur_level);
209 // Create MDO if necessary.
210 void create_mdo(const methodHandle& mh, JavaThread* thread);
211 // Is method profiled enough?
212 bool is_method_profiled(Method* method);
213
214 double _increase_threshold_at_ratio;
215
216 bool maybe_switch_to_aot(const methodHandle& mh, CompLevel cur_level, CompLevel next_level, JavaThread* thread);
217
218 protected:
219 int c1_count() const { return _c1_count; }
220 int c2_count() const { return _c2_count; }
221 void set_c1_count(int x) { _c1_count = x; }
222 void set_c2_count(int x) { _c2_count = x; }
223
224 enum EventType { CALL, LOOP, COMPILE, REMOVE_FROM_QUEUE, UPDATE_IN_QUEUE, REPROFILE, MAKE_NOT_ENTRANT };
225 void print_event(EventType type, const methodHandle& mh, const methodHandle& imh, int bci, CompLevel level);
226 // Print policy-specific information if necessary
227 virtual void print_specific(EventType type, const methodHandle& mh, const methodHandle& imh, int bci, CompLevel level);
228 // Check if the method can be compiled, change level if necessary
229 void compile(const methodHandle& mh, int bci, CompLevel level, JavaThread* thread);
230 // Submit a given method for compilation
231 virtual void submit_compile(const methodHandle& mh, int bci, CompLevel level, JavaThread* thread);
232 // Simple methods are as good being compiled with C1 as C2.
233 // This function tells if it's such a function.
234 inline bool is_trivial(Method* method);
235
236 // Predicate helpers are used by .*_predicate() methods as well as others.
237 // They check the given counter values, multiplied by the scale against the thresholds.
238 template<CompLevel level> static inline bool call_predicate_helper(int i, int b, double scale, Method* method);
239 template<CompLevel level> static inline bool loop_predicate_helper(int i, int b, double scale, Method* method);
240
241 // Get a compilation level for a given method.
242 static CompLevel comp_level(Method* method);
243 virtual void method_invocation_event(const methodHandle& method, const methodHandle& inlinee,
244 CompLevel level, CompiledMethod* nm, JavaThread* thread);
245 virtual void method_back_branch_event(const methodHandle& method, const methodHandle& inlinee,
246 int bci, CompLevel level, CompiledMethod* nm, JavaThread* thread);
247
248 void set_increase_threshold_at_ratio() { _increase_threshold_at_ratio = 100 / (100 - (double)IncreaseFirstTierCompileThresholdAt); }
249 void set_start_time(jlong t) { _start_time = t; }
250 jlong start_time() const { return _start_time; }
251
252 public:
253 SimpleThresholdPolicy() : _start_time(0), _c1_count(0), _c2_count(0) { }
254 virtual int compiler_count(CompLevel comp_level) {
255 if (is_c1_compile(comp_level)) return c1_count();
256 if (is_c2_compile(comp_level)) return c2_count();
257 return 0;
258 }
259 virtual CompLevel initial_compile_level() { return MIN2((CompLevel)TieredStopAtLevel, CompLevel_initial_compile); }
260 virtual void do_safepoint_work() { }
261 virtual void delay_compilation(Method* method) { }
262 virtual void disable_compilation(Method* method) { }
263 virtual void reprofile(ScopeDesc* trap_scope, bool is_osr);
264 virtual nmethod* event(const methodHandle& method, const methodHandle& inlinee,
265 int branch_bci, int bci, CompLevel comp_level, CompiledMethod* nm, JavaThread* thread);
266 // Select task is called by CompileBroker. We should return a task or NULL.
267 virtual CompileTask* select_task(CompileQueue* compile_queue);
268 // Tell the runtime if we think a given method is adequately profiled.
269 virtual bool is_mature(Method* method);
270 // Initialize: set compiler thread count
271 virtual void initialize();
272 virtual bool should_not_inline(ciEnv* env, ciMethod* callee);
273 };
274
275 #endif // TIERED
276
277 #endif // SHARE_VM_RUNTIME_SIMPLETHRESHOLDPOLICY_HPP
|