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comparison src/share/vm/gc_implementation/shared/gcUtil.hpp @ 6060:78a1b285cda8

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7158457: division by zero in adaptiveweightedaverage Summary: Add ceiling to AdaptiveWeightedAverage Reviewed-by: ysr, iveresov
author mikael
date Tue, 15 May 2012 00:56:06 +0200
parents f95d63e2154a
children d2a62e0f25eb
comparison
equal deleted inserted replaced
6054:56d1af561395 6060:78a1b285cda8
48 float _average; // The last computed average 48 float _average; // The last computed average
49 unsigned _sample_count; // How often we've sampled this average 49 unsigned _sample_count; // How often we've sampled this average
50 unsigned _weight; // The weight used to smooth the averages 50 unsigned _weight; // The weight used to smooth the averages
51 // A higher weight favors the most 51 // A higher weight favors the most
52 // recent data. 52 // recent data.
53 bool _is_old; // Has enough historical data
54
55 const static unsigned OLD_THRESHOLD = 100;
53 56
54 protected: 57 protected:
55 float _last_sample; // The last value sampled. 58 float _last_sample; // The last value sampled.
56 59
57 void increment_count() { _sample_count++; } 60 void increment_count() {
61 _sample_count++;
62 if (!_is_old && _sample_count > OLD_THRESHOLD) {
63 _is_old = true;
64 }
65 }
66
58 void set_average(float avg) { _average = avg; } 67 void set_average(float avg) { _average = avg; }
59 68
60 // Helper function, computes an adaptive weighted average 69 // Helper function, computes an adaptive weighted average
61 // given a sample and the last average 70 // given a sample and the last average
62 float compute_adaptive_average(float new_sample, float average); 71 float compute_adaptive_average(float new_sample, float average);
63 72
64 public: 73 public:
65 // Input weight must be between 0 and 100 74 // Input weight must be between 0 and 100
66 AdaptiveWeightedAverage(unsigned weight, float avg = 0.0) : 75 AdaptiveWeightedAverage(unsigned weight, float avg = 0.0) :
67 _average(avg), _sample_count(0), _weight(weight), _last_sample(0.0) { 76 _average(avg), _sample_count(0), _weight(weight), _last_sample(0.0),
77 _is_old(false) {
68 } 78 }
69 79
70 void clear() { 80 void clear() {
71 _average = 0; 81 _average = 0;
72 _sample_count = 0; 82 _sample_count = 0;
73 _last_sample = 0; 83 _last_sample = 0;
84 _is_old = false;
74 } 85 }
75 86
76 // Useful for modifying static structures after startup. 87 // Useful for modifying static structures after startup.
77 void modify(size_t avg, unsigned wt, bool force = false) { 88 void modify(size_t avg, unsigned wt, bool force = false) {
78 assert(force, "Are you sure you want to call this?"); 89 assert(force, "Are you sure you want to call this?");
82 93
83 // Accessors 94 // Accessors
84 float average() const { return _average; } 95 float average() const { return _average; }
85 unsigned weight() const { return _weight; } 96 unsigned weight() const { return _weight; }
86 unsigned count() const { return _sample_count; } 97 unsigned count() const { return _sample_count; }
87 float last_sample() const { return _last_sample; } 98 float last_sample() const { return _last_sample; }
99 bool is_old() const { return _is_old; }
88 100
89 // Update data with a new sample. 101 // Update data with a new sample.
90 void sample(float new_sample); 102 void sample(float new_sample);
91 103
92 static inline float exp_avg(float avg, float sample, 104 static inline float exp_avg(float avg, float sample,