C++ methodOop::backedge_count方法代码示例

// update_rate() is called from select_task() while holding a compile queue lock.
void AdvancedThresholdPolicy::update_rate(jlong t, methodOop m) {
  if (is_old(m)) {
    // We don't remove old methods from the queue,
    // so we can just zero the rate.
    m->set_rate(0);
    return;
  }

  // We don't update the rate if we've just came out of a safepoint.
  // delta_s is the time since last safepoint in milliseconds.
  jlong delta_s = t - SafepointSynchronize::end_of_last_safepoint();
  jlong delta_t = t - (m->prev_time() != 0 ? m->prev_time() : start_time()); // milliseconds since the last measurement
  // How many events were there since the last time?
  int event_count = m->invocation_count() + m->backedge_count();
  int delta_e = event_count - m->prev_event_count();

  // We should be running for at least 1ms.
  if (delta_s >= TieredRateUpdateMinTime) {
    // And we must've taken the previous point at least 1ms before.
    if (delta_t >= TieredRateUpdateMinTime && delta_e > 0) {
      m->set_prev_time(t);
      m->set_prev_event_count(event_count);
      m->set_rate((float)delta_e / (float)delta_t); // Rate is events per millisecond
    } else
      if (delta_t > TieredRateUpdateMaxTime && delta_e == 0) {
        // If nothing happened for 25ms, zero the rate. Don't modify prev values.
        m->set_rate(0);
      }
  }
}

// Check if this method has been stale from a given number of milliseconds.
// See select_task().
bool AdvancedThresholdPolicy::is_stale(jlong t, jlong timeout, methodOop m) {
  jlong delta_s = t - SafepointSynchronize::end_of_last_safepoint();
  jlong delta_t = t - m->prev_time();
  if (delta_t > timeout && delta_s > timeout) {
    int event_count = m->invocation_count() + m->backedge_count();
    int delta_e = event_count - m->prev_event_count();
    // Return true if there were no events.
    return delta_e == 0;
  }
  return false;
}

// 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.
// We also take the load on compilers into the account.
bool AdvancedThresholdPolicy::should_create_mdo(methodOop method, CompLevel cur_level) {
  if (cur_level == CompLevel_none &&
      CompileBroker::queue_size(CompLevel_full_optimization) <=
      Tier3DelayOn * compiler_count(CompLevel_full_optimization)) {
    int i = method->invocation_count();
    int b = method->backedge_count();
    double k = Tier0ProfilingStartPercentage / 100.0;
    return call_predicate_helper<CompLevel_none>(i, b, k) || loop_predicate_helper<CompLevel_none>(i, b, k);
  }
  return false;
}

// Get a measure of how much mileage the method has on it.
int methodDataOopDesc::mileage_of(methodOop method) {
  int mileage = 0;
  if (TieredCompilation) {
    mileage = MAX2(method->invocation_count(), method->backedge_count());
  } else {
    int iic = method->interpreter_invocation_count();
    if (mileage < iic)  mileage = iic;
    InvocationCounter* ic = method->invocation_counter();
    InvocationCounter* bc = method->backedge_counter();
    int icval = ic->count();
    if (ic->carry()) icval += CompileThreshold;
    if (mileage < icval)  mileage = icval;
    int bcval = bc->count();
    if (bc->carry()) bcval += CompileThreshold;
    if (mileage < bcval)  mileage = bcval;
  }
  return mileage;
}

// Common transition function. Given a predicate determines if a method should transition to another level.
CompLevel AdvancedThresholdPolicy::common(Predicate p, methodOop method, CompLevel cur_level) {
  if (is_trivial(method)) return CompLevel_simple;

  CompLevel next_level = cur_level;
  int i = method->invocation_count();
  int b = method->backedge_count();

  switch(cur_level) {
  case CompLevel_none:
    // If we were at full profile level, would we switch to full opt?
    if (common(p, method, CompLevel_full_profile) == CompLevel_full_optimization) {
      next_level = CompLevel_full_optimization;
    } else if ((this->*p)(i, b, cur_level)) {
      // C1-generated fully profiled code is about 30% slower than the limited profile
      // code that has only invocation and backedge counters. The observation is that
      // if C2 queue is large enough we can spend too much time in the fully profiled code
      // while waiting for C2 to pick the method from the queue. To alleviate this problem
      // we introduce a feedback on the C2 queue size. If the C2 queue is sufficiently long
      // we choose to compile a limited profiled version and then recompile with full profiling
      // when the load on C2 goes down.
      if (CompileBroker::queue_size(CompLevel_full_optimization) >
          Tier3DelayOn * compiler_count(CompLevel_full_optimization)) {
        next_level = CompLevel_limited_profile;
      } else {
        next_level = CompLevel_full_profile;
      }
    }
    break;
  case CompLevel_limited_profile:
    if (is_method_profiled(method)) {
      // Special case: we got here because this method was fully profiled in the interpreter.
      next_level = CompLevel_full_optimization;
    } else {
      methodDataOop mdo = method->method_data();
      if (mdo != NULL) {
        if (mdo->would_profile()) {
          if (CompileBroker::queue_size(CompLevel_full_optimization) <=
              Tier3DelayOff * compiler_count(CompLevel_full_optimization) &&
              (this->*p)(i, b, cur_level)) {
            next_level = CompLevel_full_profile;
          }
        } else {
          next_level = CompLevel_full_optimization;
        }
      }
    }
    break;
  case CompLevel_full_profile:
    {
      methodDataOop mdo = method->method_data();
      if (mdo != NULL) {
        if (mdo->would_profile()) {
          int mdo_i = mdo->invocation_count_delta();
          int mdo_b = mdo->backedge_count_delta();
          if ((this->*p)(mdo_i, mdo_b, cur_level)) {
            next_level = CompLevel_full_optimization;
          }
        } else {
          next_level = CompLevel_full_optimization;
        }
      }
    }
    break;
  }
  return next_level;
}

double AdvancedThresholdPolicy::weight(methodOop method) {
  return (method->rate() + 1) * ((method->invocation_count() + 1) *  (method->backedge_count() + 1));
}

// We don't remove old methods from the compile queue even if they have
// very low activity. See select_task().
bool AdvancedThresholdPolicy::is_old(methodOop method) {
  return method->invocation_count() > 50000 || method->backedge_count() > 500000;
}