--- a/src/hotspot/share/runtime/advancedThresholdPolicy.hpp Wed May 09 16:45:54 2018 -0700
+++ /dev/null Thu Jan 01 00:00:00 1970 +0000
@@ -1,235 +0,0 @@
-/*
- * Copyright (c) 2010, 2017, Oracle and/or its affiliates. All rights reserved.
- * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
- *
- * This code is free software; you can redistribute it and/or modify it
- * under the terms of the GNU General Public License version 2 only, as
- * published by the Free Software Foundation.
- *
- * This code is distributed in the hope that it will be useful, but WITHOUT
- * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
- * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
- * version 2 for more details (a copy is included in the LICENSE file that
- * accompanied this code).
- *
- * You should have received a copy of the GNU General Public License version
- * 2 along with this work; if not, write to the Free Software Foundation,
- * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
- *
- * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
- * or visit www.oracle.com if you need additional information or have any
- * questions.
- *
- */
-
-#ifndef SHARE_VM_RUNTIME_ADVANCEDTHRESHOLDPOLICY_HPP
-#define SHARE_VM_RUNTIME_ADVANCEDTHRESHOLDPOLICY_HPP
-
-#include "runtime/simpleThresholdPolicy.hpp"
-
-#ifdef TIERED
-class CompileTask;
-class CompileQueue;
-
-/*
- * The system supports 5 execution levels:
- * * level 0 - interpreter
- * * level 1 - C1 with full optimization (no profiling)
- * * level 2 - C1 with invocation and backedge counters
- * * level 3 - C1 with full profiling (level 2 + MDO)
- * * level 4 - C2
- *
- * Levels 0, 2 and 3 periodically notify the runtime about the current value of the counters
- * (invocation counters and backedge counters). The frequency of these notifications is
- * different at each level. These notifications are used by the policy to decide what transition
- * to make.
- *
- * Execution starts at level 0 (interpreter), then the policy can decide either to compile the
- * method at level 3 or level 2. The decision is based on the following factors:
- * 1. The length of the C2 queue determines the next level. The observation is that level 2
- * is generally faster than level 3 by about 30%, therefore we would want to minimize the time
- * a method spends at level 3. We should only spend the time at level 3 that is necessary to get
- * adequate profiling. So, if the C2 queue is long enough it is more beneficial to go first to
- * level 2, because if we transitioned to level 3 we would be stuck there until our C2 compile
- * request makes its way through the long queue. When the load on C2 recedes we are going to
- * recompile at level 3 and start gathering profiling information.
- * 2. The length of C1 queue is used to dynamically adjust the thresholds, so as to introduce
- * additional filtering if the compiler is overloaded. The rationale is that by the time a
- * method gets compiled it can become unused, so it doesn't make sense to put too much onto the
- * queue.
- *
- * After profiling is completed at level 3 the transition is made to level 4. Again, the length
- * of the C2 queue is used as a feedback to adjust the thresholds.
- *
- * After the first C1 compile some basic information is determined about the code like the number
- * of the blocks and the number of the loops. Based on that it can be decided that a method
- * is trivial and compiling it with C1 will yield the same code. In this case the method is
- * compiled at level 1 instead of 4.
- *
- * We also support profiling at level 0. If C1 is slow enough to produce the level 3 version of
- * the code and the C2 queue is sufficiently small we can decide to start profiling in the
- * interpreter (and continue profiling in the compiled code once the level 3 version arrives).
- * If the profiling at level 0 is fully completed before level 3 version is produced, a level 2
- * version is compiled instead in order to run faster waiting for a level 4 version.
- *
- * Compile queues are implemented as priority queues - for each method in the queue we compute
- * the event rate (the number of invocation and backedge counter increments per unit of time).
- * When getting an element off the queue we pick the one with the largest rate. Maintaining the
- * rate also allows us to remove stale methods (the ones that got on the queue but stopped
- * being used shortly after that).
-*/
-
-/* Command line options:
- * - Tier?InvokeNotifyFreqLog and Tier?BackedgeNotifyFreqLog control the frequency of method
- * invocation and backedge notifications. Basically every n-th invocation or backedge a mutator thread
- * makes a call into the runtime.
- *
- * - Tier?InvocationThreshold, Tier?CompileThreshold, Tier?BackEdgeThreshold, Tier?MinInvocationThreshold control
- * compilation thresholds.
- * Level 2 thresholds are not used and are provided for option-compatibility and potential future use.
- * Other thresholds work as follows:
- *
- * Transition from interpreter (level 0) to C1 with full profiling (level 3) happens when
- * the following predicate is true (X is the level):
- *
- * i > TierXInvocationThreshold * s || (i > TierXMinInvocationThreshold * s && i + b > TierXCompileThreshold * s),
- *
- * where $i$ is the number of method invocations, $b$ number of backedges and $s$ is the scaling
- * coefficient that will be discussed further.
- * The intuition is to equalize the time that is spend profiling each method.
- * The same predicate is used to control the transition from level 3 to level 4 (C2). It should be
- * noted though that the thresholds are relative. Moreover i and b for the 0->3 transition come
- * from Method* and for 3->4 transition they come from MDO (since profiled invocations are
- * counted separately). Finally, if a method does not contain anything worth profiling, a transition
- * from level 3 to level 4 occurs without considering thresholds (e.g., with fewer invocations than
- * what is specified by Tier4InvocationThreshold).
- *
- * OSR transitions are controlled simply with b > TierXBackEdgeThreshold * s predicates.
- *
- * - Tier?LoadFeedback options are used to automatically scale the predicates described above depending
- * on the compiler load. The scaling coefficients are computed as follows:
- *
- * s = queue_size_X / (TierXLoadFeedback * compiler_count_X) + 1,
- *
- * where queue_size_X is the current size of the compiler queue of level X, and compiler_count_X
- * is the number of level X compiler threads.
- *
- * Basically these parameters describe how many methods should be in the compile queue
- * per compiler thread before the scaling coefficient increases by one.
- *
- * This feedback provides the mechanism to automatically control the flow of compilation requests
- * depending on the machine speed, mutator load and other external factors.
- *
- * - Tier3DelayOn and Tier3DelayOff parameters control another important feedback loop.
- * Consider the following observation: a method compiled with full profiling (level 3)
- * is about 30% slower than a method at level 2 (just invocation and backedge counters, no MDO).
- * Normally, the following transitions will occur: 0->3->4. The problem arises when the C2 queue
- * gets congested and the 3->4 transition is delayed. While the method is the C2 queue it continues
- * executing at level 3 for much longer time than is required by the predicate and at suboptimal speed.
- * The idea is to dynamically change the behavior of the system in such a way that if a substantial
- * load on C2 is detected we would first do the 0->2 transition allowing a method to run faster.
- * And then when the load decreases to allow 2->3 transitions.
- *
- * Tier3Delay* parameters control this switching mechanism.
- * Tier3DelayOn is the number of methods in the C2 queue per compiler thread after which the policy
- * no longer does 0->3 transitions but does 0->2 transitions instead.
- * Tier3DelayOff switches the original behavior back when the number of methods in the C2 queue
- * per compiler thread falls below the specified amount.
- * The hysteresis is necessary to avoid jitter.
- *
- * - TieredCompileTaskTimeout is the amount of time an idle method can spend in the compile queue.
- * Basically, since we use the event rate d(i + b)/dt as a value of priority when selecting a method to
- * compile from the compile queue, we also can detect stale methods for which the rate has been
- * 0 for some time in the same iteration. Stale methods can appear in the queue when an application
- * abruptly changes its behavior.
- *
- * - TieredStopAtLevel, is used mostly for testing. It allows to bypass the policy logic and stick
- * to a given level. For example it's useful to set TieredStopAtLevel = 1 in order to compile everything
- * with pure c1.
- *
- * - Tier0ProfilingStartPercentage allows the interpreter to start profiling when the inequalities in the
- * 0->3 predicate are already exceeded by the given percentage but the level 3 version of the
- * method is still not ready. We can even go directly from level 0 to 4 if c1 doesn't produce a compiled
- * version in time. This reduces the overall transition to level 4 and decreases the startup time.
- * Note that this behavior is also guarded by the Tier3Delay mechanism: when the c2 queue is too long
- * these is not reason to start profiling prematurely.
- *
- * - TieredRateUpdateMinTime and TieredRateUpdateMaxTime are parameters of the rate computation.
- * Basically, the rate is not computed more frequently than TieredRateUpdateMinTime and is considered
- * to be zero if no events occurred in TieredRateUpdateMaxTime.
- */
-
-
-class AdvancedThresholdPolicy : public SimpleThresholdPolicy {
- jlong _start_time;
-
- // Call and loop predicates determine whether a transition to a higher compilation
- // level should be performed (pointers to predicate functions are passed to common().
- // Predicates also take compiler load into account.
- typedef bool (AdvancedThresholdPolicy::*Predicate)(int i, int b, CompLevel cur_level, Method* method);
- bool call_predicate(int i, int b, CompLevel cur_level, Method* method);
- bool loop_predicate(int i, int b, CompLevel cur_level, Method* method);
- // Common transition function. Given a predicate determines if a method should transition to another level.
- CompLevel common(Predicate p, Method* method, CompLevel cur_level, bool disable_feedback = false);
- // Transition functions.
- // call_event determines if a method should be compiled at a different
- // level with a regular invocation entry.
- CompLevel call_event(Method* method, CompLevel cur_level, JavaThread * thread);
- // loop_event checks if a method should be OSR compiled at a different
- // level.
- CompLevel loop_event(Method* method, CompLevel cur_level, JavaThread * thread);
- // Has a method been long around?
- // We don't remove old methods from the compile queue even if they have
- // very low activity (see select_task()).
- inline bool is_old(Method* method);
- // Was a given method inactive for a given number of milliseconds.
- // If it is, we would remove it from the queue (see select_task()).
- inline bool is_stale(jlong t, jlong timeout, Method* m);
- // Compute the weight of the method for the compilation scheduling
- inline double weight(Method* method);
- // Apply heuristics and return true if x should be compiled before y
- inline bool compare_methods(Method* x, Method* y);
- // Compute event rate for a given method. The rate is the number of event (invocations + backedges)
- // per millisecond.
- inline void update_rate(jlong t, Method* m);
- // Compute threshold scaling coefficient
- inline double threshold_scale(CompLevel level, int feedback_k);
- // If a method is old enough and is still in the interpreter we would want to
- // start profiling without waiting for the compiled method to arrive. This function
- // determines whether we should do that.
- inline bool should_create_mdo(Method* method, CompLevel cur_level);
- // Create MDO if necessary.
- void create_mdo(const methodHandle& mh, JavaThread* thread);
- // Is method profiled enough?
- bool is_method_profiled(Method* method);
-
- double _increase_threshold_at_ratio;
-
- bool maybe_switch_to_aot(const methodHandle& mh, CompLevel cur_level, CompLevel next_level, JavaThread* thread);
-
-protected:
- void print_specific(EventType type, const methodHandle& mh, const methodHandle& imh, int bci, CompLevel level);
-
- void set_increase_threshold_at_ratio() { _increase_threshold_at_ratio = 100 / (100 - (double)IncreaseFirstTierCompileThresholdAt); }
- void set_start_time(jlong t) { _start_time = t; }
- jlong start_time() const { return _start_time; }
-
- // Submit a given method for compilation (and update the rate).
- virtual void submit_compile(const methodHandle& mh, int bci, CompLevel level, JavaThread* thread);
- // event() from SimpleThresholdPolicy would call these.
- virtual void method_invocation_event(const methodHandle& method, const methodHandle& inlinee,
- CompLevel level, CompiledMethod* nm, JavaThread* thread);
- virtual void method_back_branch_event(const methodHandle& method, const methodHandle& inlinee,
- int bci, CompLevel level, CompiledMethod* nm, JavaThread* thread);
-public:
- AdvancedThresholdPolicy() : _start_time(0) { }
- // Select task is called by CompileBroker. We should return a task or NULL.
- virtual CompileTask* select_task(CompileQueue* compile_queue);
- virtual void initialize();
- virtual bool should_not_inline(ciEnv* env, ciMethod* callee);
-
-};
-
-#endif // TIERED
-
-#endif // SHARE_VM_RUNTIME_ADVANCEDTHRESHOLDPOLICY_HPP