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8015237: Parallelize string table scanning during strong root processing

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Parallelize the scanning of the intern string table by having each GC worker claim a given number of buckets. Changes were also reviewed by Per Liden <per.liden@oracle.com>.

Reviewed-by: tschatzl, stefank, twisti
This commit is contained in:
John Cuthbertson 2013-06-18 12:31:07 -07:00
parent f18e968d43
commit 5382e0759e
3 changed files with 63 additions and 10 deletions
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37
hotspot/src/share/vm/classfile/symbolTable.cpp
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@ -598,6 +598,8 @@ StringTable* StringTable::_the_table = NULL;
bool StringTable::_needs_rehashing = false;
volatile int StringTable::_parallel_claimed_idx = 0;
// Pick hashing algorithm
unsigned int StringTable::hash_string(const jchar* s, int len) {
return use_alternate_hashcode() ? AltHashing::murmur3_32(seed(), s, len) :
@ -761,8 +763,18 @@ void StringTable::unlink_or_oops_do(BoolObjectClosure* is_alive, OopClosure* f)
}
}
void StringTable::oops_do(OopClosure* f) {
for (int i = 0; i < the_table()->table_size(); ++i) {
void StringTable::buckets_do(OopClosure* f, int start_idx, int end_idx) {
const int limit = the_table()->table_size();
assert(0 <= start_idx && start_idx <= limit,
err_msg("start_idx (" INT32_FORMAT ") oob?", start_idx));
assert(0 <= end_idx && end_idx <= limit,
err_msg("end_idx (" INT32_FORMAT ") oob?", end_idx));
assert(start_idx <= end_idx,
err_msg("Ordering: start_idx=" INT32_FORMAT", end_idx=" INT32_FORMAT,
start_idx, end_idx));
for (int i = start_idx; i < end_idx; i += 1) {
HashtableEntry<oop, mtSymbol>* entry = the_table()->bucket(i);
while (entry != NULL) {
assert(!entry->is_shared(), "CDS not used for the StringTable");
@ -774,6 +786,27 @@ void StringTable::oops_do(OopClosure* f) {
}
}
void StringTable::oops_do(OopClosure* f) {
buckets_do(f, 0, the_table()->table_size());
}
void StringTable::possibly_parallel_oops_do(OopClosure* f) {
const int ClaimChunkSize = 32;
const int limit = the_table()->table_size();
for (;;) {
// Grab next set of buckets to scan
int start_idx = Atomic::add(ClaimChunkSize, &_parallel_claimed_idx) - ClaimChunkSize;
if (start_idx >= limit) {
// End of table
break;
}
int end_idx = MIN2(limit, start_idx + ClaimChunkSize);
buckets_do(f, start_idx, end_idx);
}
}
void StringTable::verify() {
for (int i = 0; i < the_table()->table_size(); ++i) {
HashtableEntry<oop, mtSymbol>* p = the_table()->bucket(i);