src/hotspot/share/utilities/globalDefinitions.hpp

rev 53303 : 8217315: Proper units should print more significant digits
Reviewed-by: XXX

*** 228,262 ****
  const int NANOUNITS     = 1000000000;   // nano units per base unit
  
  const jlong NANOSECS_PER_SEC      = CONST64(1000000000);
  const jint  NANOSECS_PER_MILLISEC = 1000000;
  
  inline const char* proper_unit_for_byte_size(size_t s) {
  #ifdef _LP64
!   if (s >= 10*G) {
      return "G";
    }
  #endif
!   if (s >= 10*M) {
      return "M";
!   } else if (s >= 10*K) {
      return "K";
    } else {
      return "B";
    }
  }
  
  template <class T>
  inline T byte_size_in_proper_unit(T s) {
  #ifdef _LP64
!   if (s >= 10*G) {
      return (T)(s/G);
    }
  #endif
!   if (s >= 10*M) {
      return (T)(s/M);
!   } else if (s >= 10*K) {
      return (T)(s/K);
    } else {
      return s;
    }
  }
--- 228,267 ----
  const int NANOUNITS     = 1000000000;   // nano units per base unit
  
  const jlong NANOSECS_PER_SEC      = CONST64(1000000000);
  const jint  NANOSECS_PER_MILLISEC = 1000000;
  
+ // Proper units routines try to maintain at least three significant digits.
+ // In worst case, it would print five significant digits with lower prefix.
+ // G is close to MAX_SIZE on 32-bit platforms, so its product can easily overflow,
+ // and therefore we need to be careful.
+ 
  inline const char* proper_unit_for_byte_size(size_t s) {
  #ifdef _LP64
!   if (s >= 100*G) {
      return "G";
    }
  #endif
!   if (s >= 100*M) {
      return "M";
!   } else if (s >= 100*K) {
      return "K";
    } else {
      return "B";
    }
  }
  
  template <class T>
  inline T byte_size_in_proper_unit(T s) {
  #ifdef _LP64
!   if (s >= 100*G) {
      return (T)(s/G);
    }
  #endif
!   if (s >= 100*M) {
      return (T)(s/M);
!   } else if (s >= 100*K) {
      return (T)(s/K);
    } else {
      return s;
    }
  }