6794422: Perm gen expansion policy for concurrent collectors
Summary: Concurrent collectors should expand the perm gen without a full STW GC, but possibly by triggering a concurrent collection. Temporary band-aid for G1 where no concurrent collection is kicked off since the perm gen is not collected concurrently.
Reviewed-by: johnc
--- a/hotspot/src/share/vm/gc_implementation/concurrentMarkSweep/cmsPermGen.cpp Thu Sep 30 12:15:13 2010 -0700
+++ b/hotspot/src/share/vm/gc_implementation/concurrentMarkSweep/cmsPermGen.cpp Fri Oct 01 16:12:54 2010 -0700
@@ -1,5 +1,5 @@
/*
- * Copyright (c) 2007, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2007, 2010, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
@@ -50,6 +50,18 @@
}
}
+HeapWord* CMSPermGen::request_expand_and_allocate(Generation* gen,
+ size_t size,
+ GCCause::Cause prev_cause /* ignored */) {
+ HeapWord* obj = gen->expand_and_allocate(size, false);
+ if (gen->capacity() >= _capacity_expansion_limit) {
+ set_capacity_expansion_limit(gen->capacity() + MaxPermHeapExpansion);
+ assert(((ConcurrentMarkSweepGeneration*)gen)->should_concurrent_collect(),
+ "Should kick off a collection if one not in progress");
+ }
+ return obj;
+}
+
void CMSPermGen::compute_new_size() {
_gen->compute_new_size();
}
--- a/hotspot/src/share/vm/gc_implementation/concurrentMarkSweep/cmsPermGen.hpp Thu Sep 30 12:15:13 2010 -0700
+++ b/hotspot/src/share/vm/gc_implementation/concurrentMarkSweep/cmsPermGen.hpp Fri Oct 01 16:12:54 2010 -0700
@@ -33,6 +33,10 @@
// The "generation" view.
ConcurrentMarkSweepGeneration* _gen;
+ // Override default implementation from PermGen
+ virtual HeapWord* request_expand_and_allocate(Generation* gen, size_t size,
+ GCCause::Cause prev_cause);
+
public:
CMSPermGen(ReservedSpace rs, size_t initial_byte_size,
CardTableRS* ct, FreeBlockDictionary::DictionaryChoice);
--- a/hotspot/src/share/vm/includeDB_core Thu Sep 30 12:15:13 2010 -0700
+++ b/hotspot/src/share/vm/includeDB_core Fri Oct 01 16:12:54 2010 -0700
@@ -3456,6 +3456,7 @@
permGen.hpp generation.hpp
permGen.hpp handles.hpp
permGen.hpp iterator.hpp
+permGen.hpp mutexLocker.hpp
permGen.hpp virtualspace.hpp
placeholders.cpp fieldType.hpp
--- a/hotspot/src/share/vm/memory/permGen.cpp Thu Sep 30 12:15:13 2010 -0700
+++ b/hotspot/src/share/vm/memory/permGen.cpp Fri Oct 01 16:12:54 2010 -0700
@@ -1,5 +1,5 @@
/*
- * Copyright (c) 2000, 2009, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2000, 2010, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
@@ -25,6 +25,17 @@
#include "incls/_precompiled.incl"
#include "incls/_permGen.cpp.incl"
+HeapWord* PermGen::request_expand_and_allocate(Generation* gen, size_t size,
+ GCCause::Cause prev_cause) {
+ if (gen->capacity() < _capacity_expansion_limit ||
+ prev_cause != GCCause::_no_gc || UseG1GC) { // last disjunct is a temporary hack for G1
+ return gen->expand_and_allocate(size, false);
+ }
+ // We have reached the limit of capacity expansion where
+ // we will not expand further until a GC is done; request denied.
+ return NULL;
+}
+
HeapWord* PermGen::mem_allocate_in_gen(size_t size, Generation* gen) {
GCCause::Cause next_cause = GCCause::_permanent_generation_full;
GCCause::Cause prev_cause = GCCause::_no_gc;
@@ -37,10 +48,14 @@
if ((obj = gen->allocate(size, false)) != NULL) {
return obj;
}
- if (gen->capacity() < _capacity_expansion_limit ||
- prev_cause != GCCause::_no_gc) {
- obj = gen->expand_and_allocate(size, false);
- }
+ // Attempt to expand and allocate the requested space:
+ // specific subtypes may use specific policy to either expand
+ // or not. The default policy (see above) is to expand until
+ // _capacity_expansion_limit, and no further unless a GC is done.
+ // Concurrent collectors may decide to kick off a concurrent
+ // collection under appropriate conditions.
+ obj = request_expand_and_allocate(gen, size, prev_cause);
+
if (obj != NULL || prev_cause == GCCause::_last_ditch_collection) {
return obj;
}
@@ -119,5 +134,5 @@
if (_gen->capacity() > desired_capacity) {
_gen->shrink(_gen->capacity() - desired_capacity);
}
- _capacity_expansion_limit = _gen->capacity() + MaxPermHeapExpansion;
+ set_capacity_expansion_limit(_gen->capacity() + MaxPermHeapExpansion);
}
--- a/hotspot/src/share/vm/memory/permGen.hpp Thu Sep 30 12:15:13 2010 -0700
+++ b/hotspot/src/share/vm/memory/permGen.hpp Fri Oct 01 16:12:54 2010 -0700
@@ -1,5 +1,5 @@
/*
- * Copyright (c) 2000, 2008, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2000, 2010, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
@@ -30,15 +30,26 @@
class GenRemSet;
class CSpaceCounters;
-// PermGen models the part of the heap
+// PermGen models the part of the heap used to allocate class meta-data.
class PermGen : public CHeapObj {
friend class VMStructs;
protected:
size_t _capacity_expansion_limit; // maximum expansion allowed without a
// full gc occurring
+ void set_capacity_expansion_limit(size_t limit) {
+ assert_locked_or_safepoint(Heap_lock);
+ _capacity_expansion_limit = limit;
+ }
HeapWord* mem_allocate_in_gen(size_t size, Generation* gen);
+ // Along with mem_allocate_in_gen() above, implements policy for
+ // "scheduling" allocation/expansion/collection of the perm gen.
+ // The virtual method request_...() below can be overridden by
+ // subtypes that want to implement a different expansion/collection
+ // policy from the default provided.
+ virtual HeapWord* request_expand_and_allocate(Generation* gen, size_t size,
+ GCCause::Cause prev_cause);
public:
enum Name {