8015422: Large performance hit when the StringTable is walked twice in Parallel Scavenge
Summary: Combine the calls to StringTable::unlink and StringTable::oops_do in Parallel Scavenge.
Reviewed-by: pliden, coleenp
--- a/hotspot/src/share/vm/classfile/symbolTable.cpp Mon May 27 12:56:34 2013 +0200
+++ b/hotspot/src/share/vm/classfile/symbolTable.cpp Mon May 27 12:58:42 2013 +0200
@@ -737,7 +737,7 @@
return result;
}
-void StringTable::unlink(BoolObjectClosure* is_alive) {
+void StringTable::unlink_or_oops_do(BoolObjectClosure* is_alive, OopClosure* f) {
// Readers of the table are unlocked, so we should only be removing
// entries at a safepoint.
assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");
@@ -748,6 +748,9 @@
assert(!entry->is_shared(), "CDS not used for the StringTable");
if (is_alive->do_object_b(entry->literal())) {
+ if (f != NULL) {
+ f->do_oop((oop*)entry->literal_addr());
+ }
p = entry->next_addr();
} else {
*p = entry->next();
--- a/hotspot/src/share/vm/classfile/symbolTable.hpp Mon May 27 12:56:34 2013 +0200
+++ b/hotspot/src/share/vm/classfile/symbolTable.hpp Mon May 27 12:58:42 2013 +0200
@@ -272,7 +272,10 @@
// GC support
// Delete pointers to otherwise-unreachable objects.
- static void unlink(BoolObjectClosure* cl);
+ static void unlink_or_oops_do(BoolObjectClosure* cl, OopClosure* f);
+ static void unlink(BoolObjectClosure* cl) {
+ unlink_or_oops_do(cl, NULL);
+ }
// Invoke "f->do_oop" on the locations of all oops in the table.
static void oops_do(OopClosure* f);
--- a/hotspot/src/share/vm/gc_implementation/parallelScavenge/psScavenge.cpp Mon May 27 12:56:34 2013 +0200
+++ b/hotspot/src/share/vm/gc_implementation/parallelScavenge/psScavenge.cpp Mon May 27 12:58:42 2013 +0200
@@ -450,11 +450,9 @@
reference_processor()->enqueue_discovered_references(NULL);
}
- // Unlink any dead interned Strings
- StringTable::unlink(&_is_alive_closure);
- // Process the remaining live ones
- PSScavengeRootsClosure root_closure(promotion_manager);
- StringTable::oops_do(&root_closure);
+ // Unlink any dead interned Strings and process the remaining live ones.
+ PSScavengeRootsClosure root_closure(promotion_manager);
+ StringTable::unlink_or_oops_do(&_is_alive_closure, &root_closure);
// Finally, flush the promotion_manager's labs, and deallocate its stacks.
PSPromotionManager::post_scavenge();