jdk8-mips64-public/hotspot: src/share/vm/runtime/advancedThresholdPolicy.hpp@01147d8aac1d (annotated)

src/share/vm/runtime/advancedThresholdPolicy.hpp@01147d8aac1d (annotated)

src/share/vm/runtime/advancedThresholdPolicy.hpp

Tue, 26 Apr 2011 14:04:43 -0400

author: coleenp
date: Tue, 26 Apr 2011 14:04:43 -0400
changeset 2804: 01147d8aac1d
parent 2630: 5d8f5a6dced7
child 2890: 97b64f73103b
permissions: -rw-r--r--

7009923: JSR 292: VM crash in JavaThread::last_frame
Summary: Handle stack overflow before the first frame is called, by printing out the called method and not walking the stack.
Reviewed-by: dholmes, phh, dsamersoff

 /*
 * Copyright (c) 2010, 2011 Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */
 #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 methodOop 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, methodOop method, CompLevel cur_level);
   // Transition functions.
   // call_event determines if a method should be compiled at a different
   // level with a regular invocation entry.
   CompLevel call_event(methodOop method, CompLevel cur_level);
   // loop_event checks if a method should be OSR compiled at a different
   // level.
   CompLevel loop_event(methodOop 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(methodOop 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, methodOop m);
   // Compute the weight of the method for the compilation scheduling
   inline double weight(methodOop method);
   // Apply heuristics and return true if x should be compiled before y
   inline bool compare_methods(methodOop x, methodOop 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, methodOop 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(methodOop method, CompLevel cur_level);
   // Create MDO if necessary.
   void create_mdo(methodHandle mh, TRAPS);
   // Is method profiled enough?
   bool is_method_profiled(methodOop method);
 protected:
   void print_specific(EventType type, methodHandle mh, methodHandle imh, int bci, CompLevel level);
   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, TRAPS);
   // event() from SimpleThresholdPolicy would call these.
   virtual void method_invocation_event(methodHandle method, methodHandle inlinee,
                                        CompLevel level, TRAPS);
   virtual void method_back_branch_event(methodHandle method, methodHandle inlinee,
                                         int bci, CompLevel level, TRAPS);
 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();
 };
 #endif // TIERED
 #endif // SHARE_VM_RUNTIME_ADVANCEDTHRESHOLDPOLICY_HPP

Mercurial > jdk8-mips64-public > hotspot / annotate

src/share/vm/runtime/advancedThresholdPolicy.hpp@01147d8aac1d (annotated)

src/share/vm/runtime/advancedThresholdPolicy.hpp