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8056084: Refactor Hashtable to allow implementations without rehashing support

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Reviewed-by: gziemski, jmasa, brutisso, coleenp, tschatzl
This commit is contained in:
Mikael Gerdin 2014-08-29 13:08:01 +02:00
parent f12e5848bd
commit 6fc8764c65
6 changed files with 61 additions and 41 deletions
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50
hotspot/src/share/vm/utilities/hashtable.cpp
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@ -37,21 +37,22 @@
#include "utilities/numberSeq.hpp"
// This is a generic hashtable, designed to be used for the symbol
// and string tables.
//
// It is implemented as an open hash table with a fixed number of buckets.
//
// %note:
// - HashtableEntrys are allocated in blocks to reduce the space overhead.
// This hashtable is implemented as an open hash table with a fixed number of buckets.
template <MEMFLAGS F> BasicHashtableEntry<F>* BasicHashtable<F>::new_entry(unsigned int hashValue) {
BasicHashtableEntry<F>* entry;
if (_free_list) {
template <MEMFLAGS F> BasicHashtableEntry<F>* BasicHashtable<F>::new_entry_free_list() {
BasicHashtableEntry<F>* entry = NULL;
if (_free_list != NULL) {
entry = _free_list;
_free_list = _free_list->next();
} else {
}
return entry;
}
// HashtableEntrys are allocated in blocks to reduce the space overhead.
template <MEMFLAGS F> BasicHashtableEntry<F>* BasicHashtable<F>::new_entry(unsigned int hashValue) {
BasicHashtableEntry<F>* entry = new_entry_free_list();
if (entry == NULL) {
if (_first_free_entry + _entry_size >= _end_block) {
int block_size = MIN2(512, MAX2((int)_table_size / 2, (int)_number_of_entries));
int len = _entry_size * block_size;
@ -84,9 +85,9 @@ template <class T, MEMFLAGS F> HashtableEntry<T, F>* Hashtable<T, F>::new_entry(
// This is somewhat an arbitrary heuristic but if one bucket gets to
// rehash_count which is currently 100, there's probably something wrong.
template <MEMFLAGS F> bool BasicHashtable<F>::check_rehash_table(int count) {
assert(table_size() != 0, "underflow");
if (count > (((double)number_of_entries()/(double)table_size())*rehash_multiple)) {
template <class T, MEMFLAGS F> bool RehashableHashtable<T, F>::check_rehash_table(int count) {
assert(this->table_size() != 0, "underflow");
if (count > (((double)this->number_of_entries()/(double)this->table_size())*rehash_multiple)) {
// Set a flag for the next safepoint, which should be at some guaranteed
// safepoint interval.
return true;
@ -94,13 +95,13 @@ template <MEMFLAGS F> bool BasicHashtable<F>::check_rehash_table(int count) {
return false;
}
template <class T, MEMFLAGS F> juint Hashtable<T, F>::_seed = 0;
template <class T, MEMFLAGS F> juint RehashableHashtable<T, F>::_seed = 0;
// Create a new table and using alternate hash code, populate the new table
// with the existing elements. This can be used to change the hash code
// and could in the future change the size of the table.
template <class T, MEMFLAGS F> void Hashtable<T, F>::move_to(Hashtable<T, F>* new_table) {
template <class T, MEMFLAGS F> void RehashableHashtable<T, F>::move_to(RehashableHashtable<T, F>* new_table) {
// Initialize the global seed for hashing.
_seed = AltHashing::compute_seed();
@ -110,7 +111,7 @@ template <class T, MEMFLAGS F> void Hashtable<T, F>::move_to(Hashtable<T, F>* ne
// Iterate through the table and create a new entry for the new table
for (int i = 0; i < new_table->table_size(); ++i) {
for (HashtableEntry<T, F>* p = bucket(i); p != NULL; ) {
for (HashtableEntry<T, F>* p = this->bucket(i); p != NULL; ) {
HashtableEntry<T, F>* next = p->next();
T string = p->literal();
// Use alternate hashing algorithm on the symbol in the first table
@ -239,11 +240,11 @@ template <class T, MEMFLAGS F> void Hashtable<T, F>::reverse(void* boundary) {
}
}
template <class T, MEMFLAGS F> int Hashtable<T, F>::literal_size(Symbol *symbol) {
template <class T, MEMFLAGS F> int RehashableHashtable<T, F>::literal_size(Symbol *symbol) {
return symbol->size() * HeapWordSize;
}
template <class T, MEMFLAGS F> int Hashtable<T, F>::literal_size(oop oop) {
template <class T, MEMFLAGS F> int RehashableHashtable<T, F>::literal_size(oop oop) {
// NOTE: this would over-count if (pre-JDK8) java_lang_Class::has_offset_field() is true,
// and the String.value array is shared by several Strings. However, starting from JDK8,
// the String.value array is not shared anymore.
@ -256,12 +257,12 @@ template <class T, MEMFLAGS F> int Hashtable<T, F>::literal_size(oop oop) {
// Note: if you create a new subclass of Hashtable<MyNewType, F>, you will need to
// add a new function Hashtable<T, F>::literal_size(MyNewType lit)
template <class T, MEMFLAGS F> void Hashtable<T, F>::dump_table(outputStream* st, const char *table_name) {
template <class T, MEMFLAGS F> void RehashableHashtable<T, F>::dump_table(outputStream* st, const char *table_name) {
NumberSeq summary;
int literal_bytes = 0;
for (int i = 0; i < this->table_size(); ++i) {
int count = 0;
for (HashtableEntry<T, F>* e = bucket(i);
for (HashtableEntry<T, F>* e = this->bucket(i);
e != NULL; e = e->next()) {
count++;
literal_bytes += literal_size(e->literal());
@ -271,7 +272,7 @@ template <class T, MEMFLAGS F> void Hashtable<T, F>::dump_table(outputStream* st
double num_buckets = summary.num();
double num_entries = summary.sum();
int bucket_bytes = (int)num_buckets * sizeof(bucket(0));
int bucket_bytes = (int)num_buckets * sizeof(HashtableBucket<F>);
int entry_bytes = (int)num_entries * sizeof(HashtableEntry<T, F>);
int total_bytes = literal_bytes + bucket_bytes + entry_bytes;
@ -355,11 +356,14 @@ template <MEMFLAGS F> void BasicHashtable<F>::verify_lookup_length(double load)
// Explicitly instantiate these types
template class Hashtable<ConstantPool*, mtClass>;
template class RehashableHashtable<Symbol*, mtSymbol>;
template class RehashableHashtable<oopDesc*, mtSymbol>;
template class Hashtable<Symbol*, mtSymbol>;
template class Hashtable<Klass*, mtClass>;
template class Hashtable<oop, mtClass>;
#if defined(SOLARIS) || defined(CHECK_UNHANDLED_OOPS)
template class Hashtable<oop, mtSymbol>;
template class RehashableHashtable<oop, mtSymbol>;
#endif // SOLARIS || CHECK_UNHANDLED_OOPS
template class Hashtable<oopDesc*, mtSymbol>;
template class Hashtable<Symbol*, mtClass>;