--- a/src/hotspot/share/oops/markOop.hpp Tue Aug 20 11:15:23 2019 +0100
+++ /dev/null Thu Jan 01 00:00:00 1970 +0000
@@ -1,433 +0,0 @@
-/*
- * Copyright (c) 1997, 2019, 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
- * under the terms of the GNU General Public License version 2 only, as
- * published by the Free Software Foundation.
- *
- * This code is distributed in the hope that it will be useful, but WITHOUT
- * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
- * 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).
- *
- * You should have received a copy of the GNU General Public License version
- * 2 along with this work; if not, write to the Free Software Foundation,
- * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
- *
- * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
- * or visit www.oracle.com if you need additional information or have any
- * questions.
- *
- */
-
-#ifndef SHARE_OOPS_MARKOOP_HPP
-#define SHARE_OOPS_MARKOOP_HPP
-
-#include "metaprogramming/integralConstant.hpp"
-#include "metaprogramming/primitiveConversions.hpp"
-#include "oops/oopsHierarchy.hpp"
-
-// The markWord describes the header of an object.
-//
-// Bit-format of an object header (most significant first, big endian layout below):
-//
-// 32 bits:
-// --------
-// hash:25 ------------>| age:4 biased_lock:1 lock:2 (normal object)
-// JavaThread*:23 epoch:2 age:4 biased_lock:1 lock:2 (biased object)
-// size:32 ------------------------------------------>| (CMS free block)
-// PromotedObject*:29 ---------->| promo_bits:3 ----->| (CMS promoted object)
-//
-// 64 bits:
-// --------
-// unused:25 hash:31 -->| unused:1 age:4 biased_lock:1 lock:2 (normal object)
-// JavaThread*:54 epoch:2 unused:1 age:4 biased_lock:1 lock:2 (biased object)
-// PromotedObject*:61 --------------------->| promo_bits:3 ----->| (CMS promoted object)
-// size:64 ----------------------------------------------------->| (CMS free block)
-//
-// unused:25 hash:31 -->| cms_free:1 age:4 biased_lock:1 lock:2 (COOPs && normal object)
-// JavaThread*:54 epoch:2 cms_free:1 age:4 biased_lock:1 lock:2 (COOPs && biased object)
-// narrowOop:32 unused:24 cms_free:1 unused:4 promo_bits:3 ----->| (COOPs && CMS promoted object)
-// unused:21 size:35 -->| cms_free:1 unused:7 ------------------>| (COOPs && CMS free block)
-//
-// - hash contains the identity hash value: largest value is
-// 31 bits, see os::random(). Also, 64-bit vm's require
-// a hash value no bigger than 32 bits because they will not
-// properly generate a mask larger than that: see library_call.cpp
-// and c1_CodePatterns_sparc.cpp.
-//
-// - the biased lock pattern is used to bias a lock toward a given
-// thread. When this pattern is set in the low three bits, the lock
-// is either biased toward a given thread or "anonymously" biased,
-// indicating that it is possible for it to be biased. When the
-// lock is biased toward a given thread, locking and unlocking can
-// be performed by that thread without using atomic operations.
-// When a lock's bias is revoked, it reverts back to the normal
-// locking scheme described below.
-//
-// Note that we are overloading the meaning of the "unlocked" state
-// of the header. Because we steal a bit from the age we can
-// guarantee that the bias pattern will never be seen for a truly
-// unlocked object.
-//
-// Note also that the biased state contains the age bits normally
-// contained in the object header. Large increases in scavenge
-// times were seen when these bits were absent and an arbitrary age
-// assigned to all biased objects, because they tended to consume a
-// significant fraction of the eden semispaces and were not
-// promoted promptly, causing an increase in the amount of copying
-// performed. The runtime system aligns all JavaThread* pointers to
-// a very large value (currently 128 bytes (32bVM) or 256 bytes (64bVM))
-// to make room for the age bits & the epoch bits (used in support of
-// biased locking), and for the CMS "freeness" bit in the 64bVM (+COOPs).
-//
-// [JavaThread* | epoch | age | 1 | 01] lock is biased toward given thread
-// [0 | epoch | age | 1 | 01] lock is anonymously biased
-//
-// - the two lock bits are used to describe three states: locked/unlocked and monitor.
-//
-// [ptr | 00] locked ptr points to real header on stack
-// [header | 0 | 01] unlocked regular object header
-// [ptr | 10] monitor inflated lock (header is wapped out)
-// [ptr | 11] marked used by markSweep to mark an object
-// not valid at any other time
-//
-// We assume that stack/thread pointers have the lowest two bits cleared.
-
-class BasicLock;
-class ObjectMonitor;
-class JavaThread;
-
-class markWord {
- private:
- uintptr_t _value;
-
- public:
- explicit markWord(uintptr_t value) : _value(value) {}
-
- markWord() { /* uninitialized */}
-
- // It is critical for performance that this class be trivially
- // destructable, copyable, and assignable.
-
- static markWord from_pointer(void* ptr) {
- return markWord((uintptr_t)ptr);
- }
- void* to_pointer() const {
- return (void*)_value;
- }
-
- bool operator==(const markWord& other) const {
- return _value == other._value;
- }
- bool operator!=(const markWord& other) const {
- return !operator==(other);
- }
-
- // Conversion
- uintptr_t value() const { return _value; }
-
- // Constants
- enum { age_bits = 4,
- lock_bits = 2,
- biased_lock_bits = 1,
- max_hash_bits = BitsPerWord - age_bits - lock_bits - biased_lock_bits,
- hash_bits = max_hash_bits > 31 ? 31 : max_hash_bits,
- cms_bits = LP64_ONLY(1) NOT_LP64(0),
- epoch_bits = 2
- };
-
- // The biased locking code currently requires that the age bits be
- // contiguous to the lock bits.
- enum { lock_shift = 0,
- biased_lock_shift = lock_bits,
- age_shift = lock_bits + biased_lock_bits,
- cms_shift = age_shift + age_bits,
- hash_shift = cms_shift + cms_bits,
- epoch_shift = hash_shift
- };
-
- enum { lock_mask = right_n_bits(lock_bits),
- lock_mask_in_place = lock_mask << lock_shift,
- biased_lock_mask = right_n_bits(lock_bits + biased_lock_bits),
- biased_lock_mask_in_place= biased_lock_mask << lock_shift,
- biased_lock_bit_in_place = 1 << biased_lock_shift,
- age_mask = right_n_bits(age_bits),
- age_mask_in_place = age_mask << age_shift,
- epoch_mask = right_n_bits(epoch_bits),
- epoch_mask_in_place = epoch_mask << epoch_shift,
- cms_mask = right_n_bits(cms_bits),
- cms_mask_in_place = cms_mask << cms_shift
- };
-
- const static uintptr_t hash_mask = right_n_bits(hash_bits);
- const static uintptr_t hash_mask_in_place = hash_mask << hash_shift;
-
- // Alignment of JavaThread pointers encoded in object header required by biased locking
- enum { biased_lock_alignment = 2 << (epoch_shift + epoch_bits)
- };
-
- enum { locked_value = 0,
- unlocked_value = 1,
- monitor_value = 2,
- marked_value = 3,
- biased_lock_pattern = 5
- };
-
- enum { no_hash = 0 }; // no hash value assigned
-
- enum { no_hash_in_place = (address_word)no_hash << hash_shift,
- no_lock_in_place = unlocked_value
- };
-
- enum { max_age = age_mask };
-
- enum { max_bias_epoch = epoch_mask };
-
- // Creates a markWord with all bits set to zero.
- static markWord zero() { return markWord(uintptr_t(0)); }
-
- // Biased Locking accessors.
- // These must be checked by all code which calls into the
- // ObjectSynchronizer and other code. The biasing is not understood
- // by the lower-level CAS-based locking code, although the runtime
- // fixes up biased locks to be compatible with it when a bias is
- // revoked.
- bool has_bias_pattern() const {
- return (mask_bits(value(), biased_lock_mask_in_place) == biased_lock_pattern);
- }
- JavaThread* biased_locker() const {
- assert(has_bias_pattern(), "should not call this otherwise");
- return (JavaThread*) ((intptr_t) (mask_bits(value(), ~(biased_lock_mask_in_place | age_mask_in_place | epoch_mask_in_place))));
- }
- // Indicates that the mark has the bias bit set but that it has not
- // yet been biased toward a particular thread
- bool is_biased_anonymously() const {
- return (has_bias_pattern() && (biased_locker() == NULL));
- }
- // Indicates epoch in which this bias was acquired. If the epoch
- // changes due to too many bias revocations occurring, the biases
- // from the previous epochs are all considered invalid.
- int bias_epoch() const {
- assert(has_bias_pattern(), "should not call this otherwise");
- return (mask_bits(value(), epoch_mask_in_place) >> epoch_shift);
- }
- markWord set_bias_epoch(int epoch) {
- assert(has_bias_pattern(), "should not call this otherwise");
- assert((epoch & (~epoch_mask)) == 0, "epoch overflow");
- return markWord(mask_bits(value(), ~epoch_mask_in_place) | (epoch << epoch_shift));
- }
- markWord incr_bias_epoch() {
- return set_bias_epoch((1 + bias_epoch()) & epoch_mask);
- }
- // Prototype mark for initialization
- static markWord biased_locking_prototype() {
- return markWord( biased_lock_pattern );
- }
-
- // lock accessors (note that these assume lock_shift == 0)
- bool is_locked() const {
- return (mask_bits(value(), lock_mask_in_place) != unlocked_value);
- }
- bool is_unlocked() const {
- return (mask_bits(value(), biased_lock_mask_in_place) == unlocked_value);
- }
- bool is_marked() const {
- return (mask_bits(value(), lock_mask_in_place) == marked_value);
- }
- bool is_neutral() const { return (mask_bits(value(), biased_lock_mask_in_place) == unlocked_value); }
-
- // Special temporary state of the markWord while being inflated.
- // Code that looks at mark outside a lock need to take this into account.
- bool is_being_inflated() const { return (value() == 0); }
-
- // Distinguished markword value - used when inflating over
- // an existing stacklock. 0 indicates the markword is "BUSY".
- // Lockword mutators that use a LD...CAS idiom should always
- // check for and avoid overwriting a 0 value installed by some
- // other thread. (They should spin or block instead. The 0 value
- // is transient and *should* be short-lived).
- static markWord INFLATING() { return zero(); } // inflate-in-progress
-
- // Should this header be preserved during GC?
- inline bool must_be_preserved(oop obj_containing_mark) const;
- inline bool must_be_preserved_with_bias(oop obj_containing_mark) const;
-
- // Should this header (including its age bits) be preserved in the
- // case of a promotion failure during scavenge?
- // Note that we special case this situation. We want to avoid
- // calling BiasedLocking::preserve_marks()/restore_marks() (which
- // decrease the number of mark words that need to be preserved
- // during GC) during each scavenge. During scavenges in which there
- // is no promotion failure, we actually don't need to call the above
- // routines at all, since we don't mutate and re-initialize the
- // marks of promoted objects using init_mark(). However, during
- // scavenges which result in promotion failure, we do re-initialize
- // the mark words of objects, meaning that we should have called
- // these mark word preservation routines. Currently there's no good
- // place in which to call them in any of the scavengers (although
- // guarded by appropriate locks we could make one), but the
- // observation is that promotion failures are quite rare and
- // reducing the number of mark words preserved during them isn't a
- // high priority.
- inline bool must_be_preserved_for_promotion_failure(oop obj_containing_mark) const;
- inline bool must_be_preserved_with_bias_for_promotion_failure(oop obj_containing_mark) const;
-
- // Should this header be preserved during a scavenge where CMS is
- // the old generation?
- // (This is basically the same body as must_be_preserved_for_promotion_failure(),
- // but takes the Klass* as argument instead)
- inline bool must_be_preserved_for_cms_scavenge(Klass* klass_of_obj_containing_mark) const;
- inline bool must_be_preserved_with_bias_for_cms_scavenge(Klass* klass_of_obj_containing_mark) const;
-
- // WARNING: The following routines are used EXCLUSIVELY by
- // synchronization functions. They are not really gc safe.
- // They must get updated if markWord layout get changed.
- markWord set_unlocked() const {
- return markWord(value() | unlocked_value);
- }
- bool has_locker() const {
- return ((value() & lock_mask_in_place) == locked_value);
- }
- BasicLock* locker() const {
- assert(has_locker(), "check");
- return (BasicLock*) value();
- }
- bool has_monitor() const {
- return ((value() & monitor_value) != 0);
- }
- ObjectMonitor* monitor() const {
- assert(has_monitor(), "check");
- // Use xor instead of &~ to provide one extra tag-bit check.
- return (ObjectMonitor*) (value() ^ monitor_value);
- }
- bool has_displaced_mark_helper() const {
- return ((value() & unlocked_value) == 0);
- }
- markWord displaced_mark_helper() const {
- assert(has_displaced_mark_helper(), "check");
- intptr_t ptr = (value() & ~monitor_value);
- return *(markWord*)ptr;
- }
- void set_displaced_mark_helper(markWord m) const {
- assert(has_displaced_mark_helper(), "check");
- intptr_t ptr = (value() & ~monitor_value);
- ((markWord*)ptr)->_value = m._value;
- }
- markWord copy_set_hash(intptr_t hash) const {
- intptr_t tmp = value() & (~hash_mask_in_place);
- tmp |= ((hash & hash_mask) << hash_shift);
- return markWord(tmp);
- }
- // it is only used to be stored into BasicLock as the
- // indicator that the lock is using heavyweight monitor
- static markWord unused_mark() {
- return markWord(marked_value);
- }
- // the following two functions create the markWord to be
- // stored into object header, it encodes monitor info
- static markWord encode(BasicLock* lock) {
- return from_pointer(lock);
- }
- static markWord encode(ObjectMonitor* monitor) {
- intptr_t tmp = (intptr_t) monitor;
- return markWord(tmp | monitor_value);
- }
- static markWord encode(JavaThread* thread, uint age, int bias_epoch) {
- intptr_t tmp = (intptr_t) thread;
- assert(UseBiasedLocking && ((tmp & (epoch_mask_in_place | age_mask_in_place | biased_lock_mask_in_place)) == 0), "misaligned JavaThread pointer");
- assert(age <= max_age, "age too large");
- assert(bias_epoch <= max_bias_epoch, "bias epoch too large");
- return markWord(tmp | (bias_epoch << epoch_shift) | (age << age_shift) | biased_lock_pattern);
- }
-
- // used to encode pointers during GC
- markWord clear_lock_bits() { return markWord(value() & ~lock_mask_in_place); }
-
- // age operations
- markWord set_marked() { return markWord((value() & ~lock_mask_in_place) | marked_value); }
- markWord set_unmarked() { return markWord((value() & ~lock_mask_in_place) | unlocked_value); }
-
- uint age() const { return mask_bits(value() >> age_shift, age_mask); }
- markWord set_age(uint v) const {
- assert((v & ~age_mask) == 0, "shouldn't overflow age field");
- return markWord((value() & ~age_mask_in_place) | (((uintptr_t)v & age_mask) << age_shift));
- }
- markWord incr_age() const { return age() == max_age ? markWord(_value) : set_age(age() + 1); }
-
- // hash operations
- intptr_t hash() const {
- return mask_bits(value() >> hash_shift, hash_mask);
- }
-
- bool has_no_hash() const {
- return hash() == no_hash;
- }
-
- // Prototype mark for initialization
- static markWord prototype() {
- return markWord( no_hash_in_place | no_lock_in_place );
- }
-
- // Helper function for restoration of unmarked mark oops during GC
- static inline markWord prototype_for_object(oop obj);
-
- // Debugging
- void print_on(outputStream* st) const;
-
- // Prepare address of oop for placement into mark
- inline static markWord encode_pointer_as_mark(void* p) { return from_pointer(p).set_marked(); }
-
- // Recover address of oop from encoded form used in mark
- inline void* decode_pointer() { if (UseBiasedLocking && has_bias_pattern()) return NULL; return (void*)clear_lock_bits().value(); }
-
- // These markWords indicate cms free chunk blocks and not objects.
- // In 64 bit, the markWord is set to distinguish them from oops.
- // These are defined in 32 bit mode for vmStructs.
- const static uintptr_t cms_free_chunk_pattern = 0x1;
-
- // Constants for the size field.
- enum { size_shift = cms_shift + cms_bits,
- size_bits = 35 // need for compressed oops 32G
- };
- // These values are too big for Win64
- const static uintptr_t size_mask = LP64_ONLY(right_n_bits(size_bits))
- NOT_LP64(0);
- const static uintptr_t size_mask_in_place =
- (address_word)size_mask << size_shift;
-
-#ifdef _LP64
- static markWord cms_free_prototype() {
- return markWord(((intptr_t)prototype().value() & ~cms_mask_in_place) |
- ((cms_free_chunk_pattern & cms_mask) << cms_shift));
- }
- uintptr_t cms_encoding() const {
- return mask_bits(value() >> cms_shift, cms_mask);
- }
- bool is_cms_free_chunk() const {
- return is_neutral() &&
- (cms_encoding() & cms_free_chunk_pattern) == cms_free_chunk_pattern;
- }
-
- size_t get_size() const { return (size_t)(value() >> size_shift); }
- static markWord set_size_and_free(size_t size) {
- assert((size & ~size_mask) == 0, "shouldn't overflow size field");
- return markWord(((intptr_t)cms_free_prototype().value() & ~size_mask_in_place) |
- (((intptr_t)size & size_mask) << size_shift));
- }
-#endif // _LP64
-};
-
-// Support atomic operations.
-template<>
-struct PrimitiveConversions::Translate<markWord> : public TrueType {
- typedef markWord Value;
- typedef uintptr_t Decayed;
-
- static Decayed decay(const Value& x) { return x.value(); }
- static Value recover(Decayed x) { return Value(x); }
-};
-
-#endif // SHARE_OOPS_MARKOOP_HPP