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src/hotspot/share/runtime/heapMonitoring.hpp

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rev 47590 : [mq]: heap8
rev 47591 : [mq]: heap10a
rev 47592 : [mq]: heap14_rebased
rev 47593 : [mq]: heap15


  31 // Support class for sampling heap allocations across the VM.
  32 class HeapMonitoring : AllStatic {
  33  private:
  34   // Cheap random number generator
  35   static uint64_t _rnd;
  36   static jint _monitoring_rate;
  37   static bool _enabled;
  38 
  39   // Statics for the fast log
  40   static const int FastLogNumBits = 10;
  41   static const int FastLogMask = (1 << FastLogNumBits) - 1;
  42   static double _log_table[1<<FastLogNumBits];  // Constant
  43 
  44   static void pick_next_sample(JavaThread *t);
  45 
  46   // Returns the next prng value.
  47   // pRNG is: aX+b mod c with a = 0x5DEECE66D, b =  0xB, c = 1<<48
  48   // This is the lrand64 generator.
  49   static inline uint64_t next_random(uint64_t rnd) {
  50     const uint64_t PrngMult = 0x5DEECE66DLL;
  51     const uint64_t prng_add = 0xB;
  52     const uint64_t prng_mod_power = 48;
  53     const uint64_t prng_mod_mask = right_n_bits(prng_mod_power);
  54     return (PrngMult * rnd + prng_add) & prng_mod_mask;
  55   }
  56 
  57   static inline double fast_log2(const double & d) {
  58     assert(d>0, "bad value passed to assert");
  59     uint64_t x = 0;
  60     memcpy(&x, &d, sizeof(uint64_t));
  61     const uint32_t x_high = x >> 32;
  62     const uint32_t y = x_high >> (20 - FastLogNumBits) & FastLogMask;
  63     const int32_t exponent = ((x_high >> 20) & 0x7FF) - 1023;
  64     return exponent + _log_table[y];
  65   }
  66 
  67  public:
  68   /*
  69    * General note: currently none of these methods are deemed thread-safe.
  70    */
  71 
  72   // First method called by user to start the profiler:
  73   //   - Note: the lower the monitoring rate, the higher the overhead incurred.
  74   static void initialize_profiling(jint monitoring_rate, jint max_gc_storage);




  31 // Support class for sampling heap allocations across the VM.
  32 class HeapMonitoring : AllStatic {
  33  private:
  34   // Cheap random number generator
  35   static uint64_t _rnd;
  36   static jint _monitoring_rate;
  37   static bool _enabled;
  38 
  39   // Statics for the fast log
  40   static const int FastLogNumBits = 10;
  41   static const int FastLogMask = (1 << FastLogNumBits) - 1;
  42   static double _log_table[1<<FastLogNumBits];  // Constant
  43 
  44   static void pick_next_sample(JavaThread *t);
  45 
  46   // Returns the next prng value.
  47   // pRNG is: aX+b mod c with a = 0x5DEECE66D, b =  0xB, c = 1<<48
  48   // This is the lrand64 generator.
  49   static inline uint64_t next_random(uint64_t rnd) {
  50     const uint64_t PrngMult = 0x5DEECE66DLL;
  51     const uint64_t PrngAdd = 0xB;
  52     const uint64_t PrngModPower = 48;
  53     const uint64_t PrngModMask = right_n_bits(PrngModPower);
  54     return (PrngMult * rnd + PrngAdd) & PrngModMask;
  55   }
  56 
  57   static inline double fast_log2(const double & d) {
  58     assert(d>0, "bad value passed to assert");
  59     uint64_t x = 0;
  60     memcpy(&x, &d, sizeof(uint64_t));
  61     const uint32_t x_high = x >> 32;
  62     const uint32_t y = x_high >> (20 - FastLogNumBits) & FastLogMask;
  63     const int32_t exponent = ((x_high >> 20) & 0x7FF) - 1023;
  64     return exponent + _log_table[y];
  65   }
  66 
  67  public:
  68   /*
  69    * General note: currently none of these methods are deemed thread-safe.
  70    */
  71 
  72   // First method called by user to start the profiler:
  73   //   - Note: the lower the monitoring rate, the higher the overhead incurred.
  74   static void initialize_profiling(jint monitoring_rate, jint max_gc_storage);


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