6990754: Use native memory and reference counting to implement SymbolTable
Summary: move symbols from permgen into C heap and reference count them
Reviewed-by: never, acorn, jmasa, stefank
/*
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
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* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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#include "precompiled.hpp"
#include "classfile/symbolTable.hpp"
#include "classfile/systemDictionary.hpp"
#include "memory/compactingPermGenGen.hpp"
#include "memory/filemap.hpp"
#include "memory/genOopClosures.inline.hpp"
#include "memory/generation.inline.hpp"
#include "memory/generationSpec.hpp"
#include "oops/oop.inline.hpp"
#include "runtime/java.hpp"
#ifndef SERIALGC
#include "gc_implementation/concurrentMarkSweep/concurrentMarkSweepGeneration.inline.hpp"
#endif
// An ObjectClosure helper: Recursively adjust all pointers in an object
// and all objects by referenced it. Clear marks on objects in order to
// prevent visiting any object twice. This helper is used when the
// RedefineClasses() API has been called.
class AdjustSharedObjectClosure : public ObjectClosure {
public:
void do_object(oop obj) {
if (obj->is_shared_readwrite()) {
if (obj->mark()->is_marked()) {
obj->init_mark(); // Don't revisit this object.
obj->adjust_pointers(); // Adjust this object's references.
}
}
}
};
// An OopClosure helper: Recursively adjust all pointers in an object
// and all objects by referenced it. Clear marks on objects in order
// to prevent visiting any object twice.
class RecursiveAdjustSharedObjectClosure : public OopClosure {
protected:
template <class T> inline void do_oop_work(T* p) {
oop obj = oopDesc::load_decode_heap_oop_not_null(p);
if (obj->is_shared_readwrite()) {
if (obj->mark()->is_marked()) {
obj->init_mark(); // Don't revisit this object.
obj->oop_iterate(this); // Recurse - adjust objects referenced.
obj->adjust_pointers(); // Adjust this object's references.
// Special case: if a class has a read-only constant pool,
// then the read-write objects referenced by the pool must
// have their marks reset.
if (obj->klass() == Universe::instanceKlassKlassObj()) {
instanceKlass* ik = instanceKlass::cast((klassOop)obj);
constantPoolOop cp = ik->constants();
if (cp->is_shared_readonly()) {
cp->oop_iterate(this);
}
}
}
}
}
public:
virtual void do_oop(oop* p) { RecursiveAdjustSharedObjectClosure::do_oop_work(p); }
virtual void do_oop(narrowOop* p) { RecursiveAdjustSharedObjectClosure::do_oop_work(p); }
};
// We need to go through all placeholders in the system dictionary and
// try to resolve them into shared classes. Other threads might be in
// the process of loading a shared class and have strong roots on
// their stack to the class without having added the class to the
// dictionary yet. This means the class will be marked during phase 1
// but will not be unmarked during the application of the
// RecursiveAdjustSharedObjectClosure to the SystemDictionary.
class TraversePlaceholdersClosure {
public:
static void placeholders_do(Symbol* sym, oop loader) {
if (CompactingPermGenGen::is_shared(sym)) {
oop k = SystemDictionary::find_shared_class(sym);
if (k != NULL) {
RecursiveAdjustSharedObjectClosure clo;
clo.do_oop(&k);
}
}
}
};
void CompactingPermGenGen::initialize_performance_counters() {
const char* gen_name = "perm";
// Generation Counters - generation 2, 1 subspace
_gen_counters = new GenerationCounters(gen_name, 2, 1, &_virtual_space);
_space_counters = new CSpaceCounters(gen_name, 0,
_virtual_space.reserved_size(),
_the_space, _gen_counters);
}
void CompactingPermGenGen::update_counters() {
if (UsePerfData) {
_space_counters->update_all();
_gen_counters->update_all();
}
}
CompactingPermGenGen::CompactingPermGenGen(ReservedSpace rs,
ReservedSpace shared_rs,
size_t initial_byte_size,
int level, GenRemSet* remset,
ContiguousSpace* space,
PermanentGenerationSpec* spec_) :
OneContigSpaceCardGeneration(rs, initial_byte_size, MinPermHeapExpansion,
level, remset, space) {
set_spec(spec_);
if (!UseSharedSpaces && !DumpSharedSpaces) {
spec()->disable_sharing();
}
// Break virtual space into address ranges for all spaces.
if (spec()->enable_shared_spaces()) {
shared_end = (HeapWord*)(shared_rs.base() + shared_rs.size());
misccode_end = shared_end;
misccode_bottom = misccode_end - heap_word_size(spec()->misc_code_size());
miscdata_end = misccode_bottom;
miscdata_bottom = miscdata_end - heap_word_size(spec()->misc_data_size());
readwrite_end = miscdata_bottom;
readwrite_bottom =
readwrite_end - heap_word_size(spec()->read_write_size());
readonly_end = readwrite_bottom;
readonly_bottom =
readonly_end - heap_word_size(spec()->read_only_size());
shared_bottom = readonly_bottom;
unshared_end = shared_bottom;
assert((char*)shared_bottom == shared_rs.base(), "shared space mismatch");
} else {
shared_end = (HeapWord*)(rs.base() + rs.size());
misccode_end = shared_end;
misccode_bottom = shared_end;
miscdata_end = shared_end;
miscdata_bottom = shared_end;
readwrite_end = shared_end;
readwrite_bottom = shared_end;
readonly_end = shared_end;
readonly_bottom = shared_end;
shared_bottom = shared_end;
unshared_end = shared_bottom;
}
unshared_bottom = (HeapWord*) rs.base();
// Verify shared and unshared spaces adjacent.
assert((char*)shared_bottom == rs.base()+rs.size(), "shared space mismatch");
assert(unshared_end > unshared_bottom, "shared space mismatch");
// Split reserved memory into pieces.
ReservedSpace ro_rs = shared_rs.first_part(spec()->read_only_size(),
UseSharedSpaces);
ReservedSpace tmp_rs1 = shared_rs.last_part(spec()->read_only_size());
ReservedSpace rw_rs = tmp_rs1.first_part(spec()->read_write_size(),
UseSharedSpaces);
ReservedSpace tmp_rs2 = tmp_rs1.last_part(spec()->read_write_size());
ReservedSpace md_rs = tmp_rs2.first_part(spec()->misc_data_size(),
UseSharedSpaces);
ReservedSpace mc_rs = tmp_rs2.last_part(spec()->misc_data_size());
_shared_space_size = spec()->read_only_size()
+ spec()->read_write_size()
+ spec()->misc_data_size()
+ spec()->misc_code_size();
// Allocate the unshared (default) space.
_the_space = new ContigPermSpace(_bts,
MemRegion(unshared_bottom, heap_word_size(initial_byte_size)));
if (_the_space == NULL)
vm_exit_during_initialization("Could not allocate an unshared"
" CompactingPermGen Space");
// Allocate shared spaces
if (spec()->enable_shared_spaces()) {
// If mapping a shared file, the space is not committed, don't
// mangle.
NOT_PRODUCT(bool old_ZapUnusedHeapArea = ZapUnusedHeapArea;)
NOT_PRODUCT(if (UseSharedSpaces) ZapUnusedHeapArea = false;)
// Commit the memory behind the shared spaces if dumping (not
// mapping).
if (DumpSharedSpaces) {
_ro_vs.initialize(ro_rs, spec()->read_only_size());
_rw_vs.initialize(rw_rs, spec()->read_write_size());
_md_vs.initialize(md_rs, spec()->misc_data_size());
_mc_vs.initialize(mc_rs, spec()->misc_code_size());
}
// Allocate the shared spaces.
_ro_bts = new BlockOffsetSharedArray(
MemRegion(readonly_bottom,
heap_word_size(spec()->read_only_size())),
heap_word_size(spec()->read_only_size()));
_ro_space = new OffsetTableContigSpace(_ro_bts,
MemRegion(readonly_bottom, readonly_end));
_rw_bts = new BlockOffsetSharedArray(
MemRegion(readwrite_bottom,
heap_word_size(spec()->read_write_size())),
heap_word_size(spec()->read_write_size()));
_rw_space = new OffsetTableContigSpace(_rw_bts,
MemRegion(readwrite_bottom, readwrite_end));
// Restore mangling flag.
NOT_PRODUCT(ZapUnusedHeapArea = old_ZapUnusedHeapArea;)
if (_ro_space == NULL || _rw_space == NULL)
vm_exit_during_initialization("Could not allocate a shared space");
// Cover both shared spaces entirely with cards.
_rs->resize_covered_region(MemRegion(readonly_bottom, readwrite_end));
if (UseSharedSpaces) {
// Map in the regions in the shared file.
FileMapInfo* mapinfo = FileMapInfo::current_info();
size_t image_alignment = mapinfo->alignment();
CollectedHeap* ch = Universe::heap();
if ((!mapinfo->map_space(ro, ro_rs, _ro_space)) ||
(!mapinfo->map_space(rw, rw_rs, _rw_space)) ||
(!mapinfo->map_space(md, md_rs, NULL)) ||
(!mapinfo->map_space(mc, mc_rs, NULL)) ||
// check the alignment constraints
(ch == NULL || ch->kind() != CollectedHeap::GenCollectedHeap ||
image_alignment !=
((GenCollectedHeap*)ch)->gen_policy()->max_alignment())) {
// Base addresses didn't match; skip sharing, but continue
shared_rs.release();
spec()->disable_sharing();
// If -Xshare:on is specified, print out the error message and exit VM,
// otherwise, set UseSharedSpaces to false and continue.
if (RequireSharedSpaces) {
vm_exit_during_initialization("Unable to use shared archive.", NULL);
} else {
FLAG_SET_DEFAULT(UseSharedSpaces, false);
}
// Note: freeing the block offset array objects does not
// currently free up the underlying storage.
delete _ro_bts;
_ro_bts = NULL;
delete _ro_space;
_ro_space = NULL;
delete _rw_bts;
_rw_bts = NULL;
delete _rw_space;
_rw_space = NULL;
shared_end = (HeapWord*)(rs.base() + rs.size());
_rs->resize_covered_region(MemRegion(shared_bottom, shared_bottom));
}
}
// Reserved region includes shared spaces for oop.is_in_reserved().
_reserved.set_end(shared_end);
} else {
_ro_space = NULL;
_rw_space = NULL;
}
}
// Do a complete scan of the shared read write space to catch all
// objects which contain references to any younger generation. Forward
// the pointers. Avoid space_iterate, as actually visiting all the
// objects in the space will page in more objects than we need.
// Instead, use the system dictionary as strong roots into the read
// write space.
//
// If a RedefineClasses() call has been made, then we have to iterate
// over the entire shared read-write space in order to find all the
// objects that need to be forwarded. For example, it is possible for
// an nmethod to be found and marked in GC phase-1 only for the nmethod
// to be freed by the time we reach GC phase-3. The underlying method
// is still marked, but we can't (easily) find it in GC phase-3 so we
// blow up in GC phase-4. With RedefineClasses() we want replaced code
// (EMCP or obsolete) to go away (i.e., be collectible) once it is no
// longer being executed by any thread so we keep minimal attachments
// to the replaced code. However, we can't guarantee when those EMCP
// or obsolete methods will be collected so they may still be out there
// even after we've severed our minimal attachments.
void CompactingPermGenGen::pre_adjust_pointers() {
if (spec()->enable_shared_spaces()) {
if (JvmtiExport::has_redefined_a_class()) {
// RedefineClasses() requires a brute force approach
AdjustSharedObjectClosure blk;
rw_space()->object_iterate(&blk);
} else {
RecursiveAdjustSharedObjectClosure blk;
Universe::oops_do(&blk);
StringTable::oops_do(&blk);
SystemDictionary::always_strong_classes_do(&blk);
SystemDictionary::placeholders_do(TraversePlaceholdersClosure::placeholders_do);
}
}
}
#ifdef ASSERT
class VerifyMarksClearedClosure : public ObjectClosure {
public:
void do_object(oop obj) {
assert(SharedSkipVerify || !obj->mark()->is_marked(),
"Shared oop still marked?");
}
};
#endif
void CompactingPermGenGen::post_compact() {
#ifdef ASSERT
if (!SharedSkipVerify && spec()->enable_shared_spaces()) {
VerifyMarksClearedClosure blk;
rw_space()->object_iterate(&blk);
}
#endif
}
// Do not use in time-critical operations due to the possibility of paging
// in otherwise untouched or previously unread portions of the perm gen,
// for instance, the shared spaces. NOTE: Because CompactingPermGenGen
// derives from OneContigSpaceCardGeneration which is supposed to have a
// single space, and does not override its object_iterate() method,
// object iteration via that interface does not look at the objects in
// the shared spaces when using CDS. This should be fixed; see CR 6897798.
void CompactingPermGenGen::space_iterate(SpaceClosure* blk, bool usedOnly) {
OneContigSpaceCardGeneration::space_iterate(blk, usedOnly);
if (spec()->enable_shared_spaces()) {
// Making the rw_space walkable will page in the entire space, and
// is to be avoided in the case of time-critical operations.
// However, this is required for Verify and heap dump operations.
blk->do_space(ro_space());
blk->do_space(rw_space());
}
}
void CompactingPermGenGen::print_on(outputStream* st) const {
OneContigSpaceCardGeneration::print_on(st);
if (spec()->enable_shared_spaces()) {
st->print(" ro");
ro_space()->print_on(st);
st->print(" rw");
rw_space()->print_on(st);
} else {
st->print_cr("No shared spaces configured.");
}
}
// References from the perm gen to the younger generation objects may
// occur in static fields in Java classes or in constant pool references
// to String objects.
void CompactingPermGenGen::younger_refs_iterate(OopsInGenClosure* blk) {
OneContigSpaceCardGeneration::younger_refs_iterate(blk);
if (spec()->enable_shared_spaces()) {
blk->set_generation(this);
// ro_space has no younger gen refs.
_rs->younger_refs_in_space_iterate(rw_space(), blk);
blk->reset_generation();
}
}
// Shared spaces are addressed in pre_adjust_pointers.
void CompactingPermGenGen::adjust_pointers() {
the_space()->adjust_pointers();
}
void CompactingPermGenGen::compact() {
the_space()->compact();
}
size_t CompactingPermGenGen::contiguous_available() const {
// Don't include shared spaces.
return OneContigSpaceCardGeneration::contiguous_available()
- _shared_space_size;
}
size_t CompactingPermGenGen::max_capacity() const {
// Don't include shared spaces.
assert(UseSharedSpaces || (_shared_space_size == 0),
"If not used, the size of shared spaces should be 0");
return OneContigSpaceCardGeneration::max_capacity()
- _shared_space_size;
}
// No young generation references, clear this generation's main space's
// card table entries. Do NOT clear the card table entries for the
// read-only space (always clear) or the read-write space (valuable
// information).
void CompactingPermGenGen::clear_remembered_set() {
_rs->clear(MemRegion(the_space()->bottom(), the_space()->end()));
}
// Objects in this generation's main space may have moved, invalidate
// that space's cards. Do NOT invalidate the card table entries for the
// read-only or read-write spaces, as those objects never move.
void CompactingPermGenGen::invalidate_remembered_set() {
_rs->invalidate(used_region());
}
void CompactingPermGenGen::verify(bool allow_dirty) {
the_space()->verify(allow_dirty);
if (!SharedSkipVerify && spec()->enable_shared_spaces()) {
ro_space()->verify(allow_dirty);
rw_space()->verify(allow_dirty);
}
}
HeapWord* CompactingPermGenGen::unshared_bottom;
HeapWord* CompactingPermGenGen::unshared_end;
HeapWord* CompactingPermGenGen::shared_bottom;
HeapWord* CompactingPermGenGen::shared_end;
HeapWord* CompactingPermGenGen::readonly_bottom;
HeapWord* CompactingPermGenGen::readonly_end;
HeapWord* CompactingPermGenGen::readwrite_bottom;
HeapWord* CompactingPermGenGen::readwrite_end;
HeapWord* CompactingPermGenGen::miscdata_bottom;
HeapWord* CompactingPermGenGen::miscdata_end;
HeapWord* CompactingPermGenGen::misccode_bottom;
HeapWord* CompactingPermGenGen::misccode_end;
// JVM/TI RedefineClasses() support:
bool CompactingPermGenGen::remap_shared_readonly_as_readwrite() {
assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");
if (UseSharedSpaces) {
// remap the shared readonly space to shared readwrite, private
FileMapInfo* mapinfo = FileMapInfo::current_info();
if (!mapinfo->remap_shared_readonly_as_readwrite()) {
return false;
}
}
return true;
}