jdk8-mips64-public/hotspot: comparison src/share/vm/runtime/advancedThresholdPolicy.hpp

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+/*
+* Copyright (c) 2010, 2013, 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?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).
+*
+*   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);
+bool call_predicate(int i, int b, CompLevel cur_level);
+bool loop_predicate(int i, int b, CompLevel cur_level);
+// 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);
+// loop_event checks if a method should be OSR compiled at a different
+// level.
+CompLevel loop_event(Method* method, CompLevel cur_level);
+// 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(methodHandle mh, JavaThread* thread);
+// Is method profiled enough?
+bool is_method_profiled(Method* method);
+double _increase_threshold_at_ratio;
+protected:
+void print_specific(EventType type, methodHandle mh, 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(methodHandle mh, int bci, CompLevel level, JavaThread* thread);
+// event() from SimpleThresholdPolicy would call these.
+virtual void method_invocation_event(methodHandle method, methodHandle inlinee,
+CompLevel level, nmethod* nm, JavaThread* thread);
+virtual void method_back_branch_event(methodHandle method, methodHandle inlinee,
+int bci, CompLevel level, nmethod* 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

Mercurial > jdk8-mips64-public > hotspot / file comparison

comparison: src/share/vm/runtime/advancedThresholdPolicy.hpp

src/share/vm/runtime/advancedThresholdPolicy.hpp