vm/oops/markOop.hpp

39 //             hash:25 ------------>| age:4    biased_lock:1 lock:2 (normal object)
40 //             JavaThread*:23 epoch:2 age:4    biased_lock:1 lock:2 (biased object)
46 //  unused:25 hash:31 -->| unused:1   age:4    biased_lock:1 lock:2 (normal object)
47 //  JavaThread*:54 epoch:2 unused:1   age:4    biased_lock:1 lock:2 (biased object)
51 //  unused:25 hash:31 -->| cms_free:1 age:4    biased_lock:1 lock:2 (COOPs && normal object)
52 //  JavaThread*:54 epoch:2 cms_free:1 age:4    biased_lock:1 lock:2 (COOPs && biased object)
72 //    of the header. Because we steal a bit from the age we can
76 //    Note also that the biased state contains the age bits normally
78 //    times were seen when these bits were absent and an arbitrary age
84 //    to make room for the age bits & the epoch bits (used in support of
87 //    [JavaThread* | epoch | age | 1 | 01]       lock is biased toward given thread
88 //    [0           | epoch | age | 1 | 01]       lock is anonymously biased
120   // The biased locking code currently requires that the age bits be
241   // Should this header (including its age bits) be preserved in the
321   static markOop encode(JavaThread* thread, uint age, int bias_epoch) {
324     assert(age <= max_age, "age too large");
326     return (markOop) (tmp | (bias_epoch << epoch_shift) | (age << age_shift) | biased_lock_pattern);
332   // age operations
336   uint    age()               const { return mask_bits(value() >> age_shift, age_mask); }
338     assert((v & ~age_mask) == 0, "shouldn't overflow age field");
341   markOop incr_age()          const { return age() == max_age ? markOop(this) : set_age(age() + 1); }