diff --git a/src/share/vm/gc_implementation/shared/gcUtil.cpp b/src/share/vm/gc_implementation/shared/gcUtil.cpp index 5325fee218b0e42f2bee9fa205fa740a0d886542..3b9fd7a68aa8fd49f9f93d28982af63b4b6d8771 100644 --- a/src/share/vm/gc_implementation/shared/gcUtil.cpp +++ b/src/share/vm/gc_implementation/shared/gcUtil.cpp @@ -31,9 +31,15 @@ float AdaptiveWeightedAverage::compute_adaptive_average(float new_sample, float average) { // We smooth the samples by not using weight() directly until we've // had enough data to make it meaningful. We'd like the first weight - // used to be 1, the second to be 1/2, etc until we have 100/weight - // samples. - unsigned count_weight = 100/count(); + // used to be 1, the second to be 1/2, etc until we have + // OLD_THRESHOLD/weight samples. + unsigned count_weight = 0; + + // Avoid division by zero if the counter wraps (7158457) + if (!is_old()) { + count_weight = OLD_THRESHOLD/count(); + } + unsigned adaptive_weight = (MAX2(weight(), count_weight)); float new_avg = exp_avg(average, new_sample, adaptive_weight); @@ -43,8 +49,6 @@ float AdaptiveWeightedAverage::compute_adaptive_average(float new_sample, void AdaptiveWeightedAverage::sample(float new_sample) { increment_count(); - assert(count() != 0, - "Wraparound -- history would be incorrectly discarded"); // Compute the new weighted average float new_avg = compute_adaptive_average(new_sample, average()); diff --git a/src/share/vm/gc_implementation/shared/gcUtil.hpp b/src/share/vm/gc_implementation/shared/gcUtil.hpp index 8dd3258de0a89d8d5f9ccd3ac88056f69509bb99..86daba64c3f6383f7cb522c0e9479a85a871e3dc 100644 --- a/src/share/vm/gc_implementation/shared/gcUtil.hpp +++ b/src/share/vm/gc_implementation/shared/gcUtil.hpp @@ -50,11 +50,20 @@ class AdaptiveWeightedAverage : public CHeapObj { unsigned _weight; // The weight used to smooth the averages // A higher weight favors the most // recent data. + bool _is_old; // Has enough historical data + + const static unsigned OLD_THRESHOLD = 100; protected: float _last_sample; // The last value sampled. - void increment_count() { _sample_count++; } + void increment_count() { + _sample_count++; + if (!_is_old && _sample_count > OLD_THRESHOLD) { + _is_old = true; + } + } + void set_average(float avg) { _average = avg; } // Helper function, computes an adaptive weighted average @@ -64,13 +73,15 @@ class AdaptiveWeightedAverage : public CHeapObj { public: // Input weight must be between 0 and 100 AdaptiveWeightedAverage(unsigned weight, float avg = 0.0) : - _average(avg), _sample_count(0), _weight(weight), _last_sample(0.0) { + _average(avg), _sample_count(0), _weight(weight), _last_sample(0.0), + _is_old(false) { } void clear() { _average = 0; _sample_count = 0; _last_sample = 0; + _is_old = false; } // Useful for modifying static structures after startup. @@ -84,7 +95,8 @@ class AdaptiveWeightedAverage : public CHeapObj { float average() const { return _average; } unsigned weight() const { return _weight; } unsigned count() const { return _sample_count; } - float last_sample() const { return _last_sample; } + float last_sample() const { return _last_sample; } + bool is_old() const { return _is_old; } // Update data with a new sample. void sample(float new_sample);