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7158800: Improve storage of symbol tables

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Use an alternate version of hashing algorithm for symbol string tables and after a certain bucket size to improve performance

Reviewed-by: pbk, kamg, dlong, kvn, fparain
This commit is contained in:
Coleen Phillimore 2012-06-13 19:52:59 -04:00
parent 7c17e9e75b
commit 55b09e7016
17 changed files with 32031 additions and 55 deletions
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24
hotspot/src/share/vm/classfile/javaClasses.hpp
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@ -158,20 +158,16 @@ class java_lang_String : AllStatic {
static jchar* as_unicode_string(oop java_string, int& length);
// Compute the hash value for a java.lang.String object which would
// contain the characters passed in. This hash value is used for at
// least two purposes.
// contain the characters passed in.
//
// (a) As the hash value used by the StringTable for bucket selection
// and comparison (stored in the HashtableEntry structures). This
// is used in the String.intern() method.
// As the hash value used by the String object itself, in
// String.hashCode(). This value is normally calculated in Java code
// in the String.hashCode method(), but is precomputed for String
// objects in the shared archive file.
// hash P(31) from Kernighan & Ritchie
//
// (b) As the hash value used by the String object itself, in
// String.hashCode(). This value is normally calculate in Java code
// in the String.hashCode method(), but is precomputed for String
// objects in the shared archive file.
//
// For this reason, THIS ALGORITHM MUST MATCH String.hashCode().
static unsigned int hash_string(jchar* s, int len) {
// For this reason, THIS ALGORITHM MUST MATCH String.toHash().
template <typename T> static unsigned int to_hash(T* s, int len) {
unsigned int h = 0;
while (len-- > 0) {
h = 31*h + (unsigned int) *s;
@ -179,6 +175,10 @@ class java_lang_String : AllStatic {
}
return h;
}
static unsigned int to_hash(oop java_string);
// This is the string hash code used by the StringTable, which may be
// the same as String.toHash or an alternate hash code.
static unsigned int hash_string(oop java_string);
static bool equals(oop java_string, jchar* chars, int len);