duke@435: /* stefank@2314: * Copyright (c) 1997, 2010, Oracle and/or its affiliates. All rights reserved. duke@435: * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. duke@435: * duke@435: * This code is free software; you can redistribute it and/or modify it duke@435: * under the terms of the GNU General Public License version 2 only, as duke@435: * published by the Free Software Foundation. duke@435: * duke@435: * This code is distributed in the hope that it will be useful, but WITHOUT duke@435: * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or duke@435: * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License duke@435: * version 2 for more details (a copy is included in the LICENSE file that duke@435: * accompanied this code). duke@435: * duke@435: * You should have received a copy of the GNU General Public License version duke@435: * 2 along with this work; if not, write to the Free Software Foundation, duke@435: * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. duke@435: * trims@1907: * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA trims@1907: * or visit www.oracle.com if you need additional information or have any trims@1907: * questions. duke@435: * duke@435: */ duke@435: stefank@2314: #ifndef SHARE_VM_OOPS_MARKOOP_HPP stefank@2314: #define SHARE_VM_OOPS_MARKOOP_HPP stefank@2314: stefank@2314: #include "oops/oop.hpp" stefank@2314: duke@435: // The markOop describes the header of an object. duke@435: // duke@435: // Note that the mark is not a real oop but just a word. duke@435: // It is placed in the oop hierarchy for historical reasons. duke@435: // ysr@1901: // Bit-format of an object header (most significant first, big endian layout below): duke@435: // ysr@1901: // 32 bits: ysr@1901: // -------- ysr@1901: // hash:25 ------------>| age:4 biased_lock:1 lock:2 (normal object) ysr@1901: // JavaThread*:23 epoch:2 age:4 biased_lock:1 lock:2 (biased object) ysr@1901: // size:32 ------------------------------------------>| (CMS free block) ysr@1901: // PromotedObject*:29 ---------->| promo_bits:3 ----->| (CMS promoted object) ysr@1901: // ysr@1901: // 64 bits: ysr@1901: // -------- ysr@1901: // unused:25 hash:31 -->| unused:1 age:4 biased_lock:1 lock:2 (normal object) ysr@1901: // JavaThread*:54 epoch:2 unused:1 age:4 biased_lock:1 lock:2 (biased object) ysr@1901: // PromotedObject*:61 --------------------->| promo_bits:3 ----->| (CMS promoted object) ysr@1901: // size:64 ----------------------------------------------------->| (CMS free block) ysr@1901: // ysr@1901: // unused:25 hash:31 -->| cms_free:1 age:4 biased_lock:1 lock:2 (COOPs && normal object) ysr@1901: // JavaThread*:54 epoch:2 cms_free:1 age:4 biased_lock:1 lock:2 (COOPs && biased object) ysr@1901: // narrowOop:32 unused:24 cms_free:1 unused:4 promo_bits:3 ----->| (COOPs && CMS promoted object) ysr@1901: // unused:21 size:35 -->| cms_free:1 unused:7 ------------------>| (COOPs && CMS free block) duke@435: // duke@435: // - hash contains the identity hash value: largest value is duke@435: // 31 bits, see os::random(). Also, 64-bit vm's require duke@435: // a hash value no bigger than 32 bits because they will not duke@435: // properly generate a mask larger than that: see library_call.cpp duke@435: // and c1_CodePatterns_sparc.cpp. duke@435: // duke@435: // - the biased lock pattern is used to bias a lock toward a given duke@435: // thread. When this pattern is set in the low three bits, the lock duke@435: // is either biased toward a given thread or "anonymously" biased, duke@435: // indicating that it is possible for it to be biased. When the duke@435: // lock is biased toward a given thread, locking and unlocking can duke@435: // be performed by that thread without using atomic operations. duke@435: // When a lock's bias is revoked, it reverts back to the normal duke@435: // locking scheme described below. duke@435: // duke@435: // Note that we are overloading the meaning of the "unlocked" state duke@435: // of the header. Because we steal a bit from the age we can duke@435: // guarantee that the bias pattern will never be seen for a truly duke@435: // unlocked object. duke@435: // duke@435: // Note also that the biased state contains the age bits normally duke@435: // contained in the object header. Large increases in scavenge duke@435: // times were seen when these bits were absent and an arbitrary age duke@435: // assigned to all biased objects, because they tended to consume a duke@435: // significant fraction of the eden semispaces and were not duke@435: // promoted promptly, causing an increase in the amount of copying duke@435: // performed. The runtime system aligns all JavaThread* pointers to ysr@1901: // a very large value (currently 128 bytes (32bVM) or 256 bytes (64bVM)) ysr@1901: // to make room for the age bits & the epoch bits (used in support of ysr@1901: // biased locking), and for the CMS "freeness" bit in the 64bVM (+COOPs). duke@435: // duke@435: // [JavaThread* | epoch | age | 1 | 01] lock is biased toward given thread duke@435: // [0 | epoch | age | 1 | 01] lock is anonymously biased duke@435: // duke@435: // - the two lock bits are used to describe three states: locked/unlocked and monitor. duke@435: // duke@435: // [ptr | 00] locked ptr points to real header on stack duke@435: // [header | 0 | 01] unlocked regular object header duke@435: // [ptr | 10] monitor inflated lock (header is wapped out) duke@435: // [ptr | 11] marked used by markSweep to mark an object duke@435: // not valid at any other time duke@435: // duke@435: // We assume that stack/thread pointers have the lowest two bits cleared. duke@435: duke@435: class BasicLock; duke@435: class ObjectMonitor; duke@435: class JavaThread; duke@435: duke@435: class markOopDesc: public oopDesc { duke@435: private: duke@435: // Conversion duke@435: uintptr_t value() const { return (uintptr_t) this; } duke@435: duke@435: public: duke@435: // Constants duke@435: enum { age_bits = 4, duke@435: lock_bits = 2, duke@435: biased_lock_bits = 1, coleenp@548: max_hash_bits = BitsPerWord - age_bits - lock_bits - biased_lock_bits, duke@435: hash_bits = max_hash_bits > 31 ? 31 : max_hash_bits, coleenp@622: cms_bits = LP64_ONLY(1) NOT_LP64(0), duke@435: epoch_bits = 2 duke@435: }; duke@435: duke@435: // The biased locking code currently requires that the age bits be coleenp@2497: // contiguous to the lock bits. duke@435: enum { lock_shift = 0, duke@435: biased_lock_shift = lock_bits, duke@435: age_shift = lock_bits + biased_lock_bits, coleenp@622: cms_shift = age_shift + age_bits, coleenp@622: hash_shift = cms_shift + cms_bits, duke@435: epoch_shift = hash_shift duke@435: }; duke@435: duke@435: enum { lock_mask = right_n_bits(lock_bits), duke@435: lock_mask_in_place = lock_mask << lock_shift, duke@435: biased_lock_mask = right_n_bits(lock_bits + biased_lock_bits), duke@435: biased_lock_mask_in_place= biased_lock_mask << lock_shift, duke@435: biased_lock_bit_in_place = 1 << biased_lock_shift, duke@435: age_mask = right_n_bits(age_bits), duke@435: age_mask_in_place = age_mask << age_shift, duke@435: epoch_mask = right_n_bits(epoch_bits), coleenp@622: epoch_mask_in_place = epoch_mask << epoch_shift, coleenp@622: cms_mask = right_n_bits(cms_bits), coleenp@622: cms_mask_in_place = cms_mask << cms_shift duke@435: #ifndef _WIN64 duke@435: ,hash_mask = right_n_bits(hash_bits), duke@435: hash_mask_in_place = (address_word)hash_mask << hash_shift duke@435: #endif duke@435: }; duke@435: duke@435: // Alignment of JavaThread pointers encoded in object header required by biased locking duke@435: enum { biased_lock_alignment = 2 << (epoch_shift + epoch_bits) duke@435: }; duke@435: duke@435: #ifdef _WIN64 duke@435: // These values are too big for Win64 duke@435: const static uintptr_t hash_mask = right_n_bits(hash_bits); duke@435: const static uintptr_t hash_mask_in_place = duke@435: (address_word)hash_mask << hash_shift; duke@435: #endif duke@435: duke@435: enum { locked_value = 0, duke@435: unlocked_value = 1, duke@435: monitor_value = 2, duke@435: marked_value = 3, duke@435: biased_lock_pattern = 5 duke@435: }; duke@435: duke@435: enum { no_hash = 0 }; // no hash value assigned duke@435: duke@435: enum { no_hash_in_place = (address_word)no_hash << hash_shift, duke@435: no_lock_in_place = unlocked_value duke@435: }; duke@435: duke@435: enum { max_age = age_mask }; duke@435: duke@435: enum { max_bias_epoch = epoch_mask }; duke@435: duke@435: // Biased Locking accessors. duke@435: // These must be checked by all code which calls into the duke@435: // ObjectSynchronizer and other code. The biasing is not understood duke@435: // by the lower-level CAS-based locking code, although the runtime duke@435: // fixes up biased locks to be compatible with it when a bias is duke@435: // revoked. duke@435: bool has_bias_pattern() const { duke@435: return (mask_bits(value(), biased_lock_mask_in_place) == biased_lock_pattern); duke@435: } duke@435: JavaThread* biased_locker() const { duke@435: assert(has_bias_pattern(), "should not call this otherwise"); duke@435: return (JavaThread*) ((intptr_t) (mask_bits(value(), ~(biased_lock_mask_in_place | age_mask_in_place | epoch_mask_in_place)))); duke@435: } duke@435: // Indicates that the mark has the bias bit set but that it has not duke@435: // yet been biased toward a particular thread duke@435: bool is_biased_anonymously() const { duke@435: return (has_bias_pattern() && (biased_locker() == NULL)); duke@435: } duke@435: // Indicates epoch in which this bias was acquired. If the epoch duke@435: // changes due to too many bias revocations occurring, the biases duke@435: // from the previous epochs are all considered invalid. duke@435: int bias_epoch() const { duke@435: assert(has_bias_pattern(), "should not call this otherwise"); duke@435: return (mask_bits(value(), epoch_mask_in_place) >> epoch_shift); duke@435: } duke@435: markOop set_bias_epoch(int epoch) { duke@435: assert(has_bias_pattern(), "should not call this otherwise"); duke@435: assert((epoch & (~epoch_mask)) == 0, "epoch overflow"); duke@435: return markOop(mask_bits(value(), ~epoch_mask_in_place) | (epoch << epoch_shift)); duke@435: } duke@435: markOop incr_bias_epoch() { duke@435: return set_bias_epoch((1 + bias_epoch()) & epoch_mask); duke@435: } duke@435: // Prototype mark for initialization duke@435: static markOop biased_locking_prototype() { duke@435: return markOop( biased_lock_pattern ); duke@435: } duke@435: duke@435: // lock accessors (note that these assume lock_shift == 0) duke@435: bool is_locked() const { duke@435: return (mask_bits(value(), lock_mask_in_place) != unlocked_value); duke@435: } duke@435: bool is_unlocked() const { duke@435: return (mask_bits(value(), biased_lock_mask_in_place) == unlocked_value); duke@435: } duke@435: bool is_marked() const { duke@435: return (mask_bits(value(), lock_mask_in_place) == marked_value); duke@435: } duke@435: bool is_neutral() const { return (mask_bits(value(), biased_lock_mask_in_place) == unlocked_value); } duke@435: duke@435: // Special temporary state of the markOop while being inflated. duke@435: // Code that looks at mark outside a lock need to take this into account. duke@435: bool is_being_inflated() const { return (value() == 0); } duke@435: duke@435: // Distinguished markword value - used when inflating over duke@435: // an existing stacklock. 0 indicates the markword is "BUSY". duke@435: // Lockword mutators that use a LD...CAS idiom should always duke@435: // check for and avoid overwriting a 0 value installed by some duke@435: // other thread. (They should spin or block instead. The 0 value duke@435: // is transient and *should* be short-lived). duke@435: static markOop INFLATING() { return (markOop) 0; } // inflate-in-progress duke@435: duke@435: // Should this header be preserved during GC? ysr@777: inline bool must_be_preserved(oop obj_containing_mark) const; duke@435: inline bool must_be_preserved_with_bias(oop obj_containing_mark) const; duke@435: duke@435: // Should this header (including its age bits) be preserved in the duke@435: // case of a promotion failure during scavenge? duke@435: // Note that we special case this situation. We want to avoid duke@435: // calling BiasedLocking::preserve_marks()/restore_marks() (which duke@435: // decrease the number of mark words that need to be preserved duke@435: // during GC) during each scavenge. During scavenges in which there duke@435: // is no promotion failure, we actually don't need to call the above duke@435: // routines at all, since we don't mutate and re-initialize the duke@435: // marks of promoted objects using init_mark(). However, during duke@435: // scavenges which result in promotion failure, we do re-initialize duke@435: // the mark words of objects, meaning that we should have called duke@435: // these mark word preservation routines. Currently there's no good duke@435: // place in which to call them in any of the scavengers (although duke@435: // guarded by appropriate locks we could make one), but the duke@435: // observation is that promotion failures are quite rare and duke@435: // reducing the number of mark words preserved during them isn't a duke@435: // high priority. ysr@777: inline bool must_be_preserved_for_promotion_failure(oop obj_containing_mark) const; duke@435: inline bool must_be_preserved_with_bias_for_promotion_failure(oop obj_containing_mark) const; duke@435: duke@435: // Should this header be preserved during a scavenge where CMS is duke@435: // the old generation? duke@435: // (This is basically the same body as must_be_preserved_for_promotion_failure(), duke@435: // but takes the klassOop as argument instead) ysr@777: inline bool must_be_preserved_for_cms_scavenge(klassOop klass_of_obj_containing_mark) const; duke@435: inline bool must_be_preserved_with_bias_for_cms_scavenge(klassOop klass_of_obj_containing_mark) const; duke@435: duke@435: // WARNING: The following routines are used EXCLUSIVELY by duke@435: // synchronization functions. They are not really gc safe. duke@435: // They must get updated if markOop layout get changed. duke@435: markOop set_unlocked() const { duke@435: return markOop(value() | unlocked_value); duke@435: } duke@435: bool has_locker() const { duke@435: return ((value() & lock_mask_in_place) == locked_value); duke@435: } duke@435: BasicLock* locker() const { duke@435: assert(has_locker(), "check"); duke@435: return (BasicLock*) value(); duke@435: } duke@435: bool has_monitor() const { duke@435: return ((value() & monitor_value) != 0); duke@435: } duke@435: ObjectMonitor* monitor() const { duke@435: assert(has_monitor(), "check"); duke@435: // Use xor instead of &~ to provide one extra tag-bit check. duke@435: return (ObjectMonitor*) (value() ^ monitor_value); duke@435: } duke@435: bool has_displaced_mark_helper() const { duke@435: return ((value() & unlocked_value) == 0); duke@435: } duke@435: markOop displaced_mark_helper() const { duke@435: assert(has_displaced_mark_helper(), "check"); duke@435: intptr_t ptr = (value() & ~monitor_value); duke@435: return *(markOop*)ptr; duke@435: } duke@435: void set_displaced_mark_helper(markOop m) const { duke@435: assert(has_displaced_mark_helper(), "check"); duke@435: intptr_t ptr = (value() & ~monitor_value); duke@435: *(markOop*)ptr = m; duke@435: } duke@435: markOop copy_set_hash(intptr_t hash) const { duke@435: intptr_t tmp = value() & (~hash_mask_in_place); duke@435: tmp |= ((hash & hash_mask) << hash_shift); duke@435: return (markOop)tmp; duke@435: } duke@435: // it is only used to be stored into BasicLock as the duke@435: // indicator that the lock is using heavyweight monitor duke@435: static markOop unused_mark() { duke@435: return (markOop) marked_value; duke@435: } duke@435: // the following two functions create the markOop to be duke@435: // stored into object header, it encodes monitor info duke@435: static markOop encode(BasicLock* lock) { duke@435: return (markOop) lock; duke@435: } duke@435: static markOop encode(ObjectMonitor* monitor) { duke@435: intptr_t tmp = (intptr_t) monitor; duke@435: return (markOop) (tmp | monitor_value); duke@435: } duke@435: static markOop encode(JavaThread* thread, int age, int bias_epoch) { duke@435: intptr_t tmp = (intptr_t) thread; duke@435: assert(UseBiasedLocking && ((tmp & (epoch_mask_in_place | age_mask_in_place | biased_lock_mask_in_place)) == 0), "misaligned JavaThread pointer"); duke@435: assert(age <= max_age, "age too large"); duke@435: assert(bias_epoch <= max_bias_epoch, "bias epoch too large"); duke@435: return (markOop) (tmp | (bias_epoch << epoch_shift) | (age << age_shift) | biased_lock_pattern); duke@435: } duke@435: duke@435: // used to encode pointers during GC duke@435: markOop clear_lock_bits() { return markOop(value() & ~lock_mask_in_place); } duke@435: duke@435: // age operations duke@435: markOop set_marked() { return markOop((value() & ~lock_mask_in_place) | marked_value); } duke@435: duke@435: int age() const { return mask_bits(value() >> age_shift, age_mask); } duke@435: markOop set_age(int v) const { duke@435: assert((v & ~age_mask) == 0, "shouldn't overflow age field"); duke@435: return markOop((value() & ~age_mask_in_place) | (((intptr_t)v & age_mask) << age_shift)); duke@435: } duke@435: markOop incr_age() const { return age() == max_age ? markOop(this) : set_age(age() + 1); } duke@435: duke@435: // hash operations duke@435: intptr_t hash() const { duke@435: return mask_bits(value() >> hash_shift, hash_mask); duke@435: } duke@435: duke@435: bool has_no_hash() const { duke@435: return hash() == no_hash; duke@435: } duke@435: duke@435: // Prototype mark for initialization duke@435: static markOop prototype() { duke@435: return markOop( no_hash_in_place | no_lock_in_place ); duke@435: } duke@435: duke@435: // Helper function for restoration of unmarked mark oops during GC duke@435: static inline markOop prototype_for_object(oop obj); duke@435: duke@435: // Debugging duke@435: void print_on(outputStream* st) const; duke@435: duke@435: // Prepare address of oop for placement into mark duke@435: inline static markOop encode_pointer_as_mark(void* p) { return markOop(p)->set_marked(); } duke@435: duke@435: // Recover address of oop from encoded form used in mark duke@435: inline void* decode_pointer() { if (UseBiasedLocking && has_bias_pattern()) return NULL; return clear_lock_bits(); } dcubed@483: dcubed@483: // see the definition in markOop.cpp for the gory details dcubed@483: bool should_not_be_cached() const; coleenp@622: coleenp@622: // These markOops indicate cms free chunk blocks and not objects. coleenp@622: // In 64 bit, the markOop is set to distinguish them from oops. coleenp@622: // These are defined in 32 bit mode for vmStructs. coleenp@622: const static uintptr_t cms_free_chunk_pattern = 0x1; coleenp@622: coleenp@622: // Constants for the size field. coleenp@622: enum { size_shift = cms_shift + cms_bits, coleenp@622: size_bits = 35 // need for compressed oops 32G coleenp@622: }; coleenp@622: // These values are too big for Win64 coleenp@622: const static uintptr_t size_mask = LP64_ONLY(right_n_bits(size_bits)) coleenp@622: NOT_LP64(0); coleenp@622: const static uintptr_t size_mask_in_place = coleenp@622: (address_word)size_mask << size_shift; coleenp@622: coleenp@622: #ifdef _LP64 coleenp@622: static markOop cms_free_prototype() { coleenp@622: return markOop(((intptr_t)prototype() & ~cms_mask_in_place) | coleenp@622: ((cms_free_chunk_pattern & cms_mask) << cms_shift)); coleenp@622: } coleenp@622: uintptr_t cms_encoding() const { coleenp@622: return mask_bits(value() >> cms_shift, cms_mask); coleenp@622: } coleenp@622: bool is_cms_free_chunk() const { coleenp@622: return is_neutral() && coleenp@622: (cms_encoding() & cms_free_chunk_pattern) == cms_free_chunk_pattern; coleenp@622: } coleenp@622: coleenp@622: size_t get_size() const { return (size_t)(value() >> size_shift); } coleenp@622: static markOop set_size_and_free(size_t size) { coleenp@622: assert((size & ~size_mask) == 0, "shouldn't overflow size field"); coleenp@622: return markOop(((intptr_t)cms_free_prototype() & ~size_mask_in_place) | coleenp@622: (((intptr_t)size & size_mask) << size_shift)); coleenp@622: } coleenp@622: #endif // _LP64 duke@435: }; stefank@2314: stefank@2314: #endif // SHARE_VM_OOPS_MARKOOP_HPP