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NAME CK_ELIDE_PROTOTYPE, CK_ELIDE_LOCK_ADAPTIVE, CK_ELIDE_UNLOCK_ADAPTIVE, CK_ELIDE_LOCK, CK_ELIDE_UNLOCK, CK_ELIDE_TRYLOCK_PROTOTYPE, CK_ELIDE_TRYLOCK -- lock elision wrappers LIBRARY Concurrency Kit (libck, -lck) SYNOPSIS #include <ck_elide.h> ck_elide_stat_t stat = CK_ELIDE_STAT_INITIALIZER; void ck_elide_stat_init(ck_elide_stat_t *); struct ck_elide_config config = CK_ELIDE_CONFIG_DEFAULT_INITIALIZER; struct ck_elide_config { unsigned short skip_busy; short retry_busy; unsigned short skip_other; short retry_other; unsigned short skip_conflict; short retry_conflict; }; CK_ELIDE_PROTOTYPE(NAME, TYPE, LOCK_PREDICATE, LOCK_FUNCTION, UNLOCK_PREDICATE, UNLOCK_FUNCTION); CK_ELIDE_LOCK_ADAPTIVE(NAME, ck_elide_stat_t *, struct ck_elide_config *, TYPE *); CK_ELIDE_UNLOCK_ADAPTIVE(NAME, ck_elide_stat_t *, TYPE *); CK_ELIDE_LOCK(NAME, TYPE *); CK_ELIDE_UNLOCK(NAME, TYPE *); CK_ELIDE_TRYLOCK_PROTOTYPE(NAME, TYPE, LOCK_PREDICATE, TRYLOCK_FUNCTION); DESCRIPTION These macros implement lock elision wrappers for a user-specified single- argument lock interface. The wrappers will attempt to elide lock acquisi- tion, allowing concurrent execution of critical sections that do not issue conflicting memory operations. If any threads have successfully elided a lock acquisition, conflicting memory operations will roll-back any side-ef- fects of the critical section and force every thread to retry the lock ac- quisition regularly. CK_ELIDE_LOCK(), CK_ELIDE_UNLOCK(), CK_ELIDE_LOCK_ADAPTIVE(), and CK_ELIDE_UNLOCK_ADAPTIVE() macros require a previous CK_ELIDE_PROTOTYPE() with the same NAME. Elision is attempted if the LOCK_PREDICATE function returns false. If LOCK_PREDICATE returns true then elision is aborted and LOCK_FUNCTION is executed instead. If any threads are in an elided critical section, LOCK_FUNCTION must force them to rollback through a conflicting memory operation. The UNLOCK_PREDICATE function must return true if the lock is acquired by the caller, meaning that the lock was not successfully elided. If UNLOCK_PREDICATE returns true, then the UNLOCK_FUNCTION is exe- cuted. If RTM is unsupported (no CK_F_PR_RTM macro) then CK_ELIDE_LOCK() and CK_ELIDE_LOCK_ADAPTIVE() will immediately call LOCK_FUNCTION(). CK_ELIDE_UNLOCK() and CK_ELIDE_UNLOCK_ADAPTIVE() will immediately call UN- LOCK_FUNCTION(). CK_ELIDE_TRYLOCK() requires a previous CK_ELIDE_TRYLOCK_PROTOTYPE() with the same name. Elision is attempted if the LOCK_PREDICATE function returns false. If LOCK_PREDICATE returns true or if elision fails then the opera- tion is aborted. If RTM is unsupported (no CK_F_PR_RTM macro) then CK_ELIDE_TRYLOCK() will immediately call TRYLOCK_FUNCTION(). CK_ELIDE_LOCK_ADAPTIVE() and CK_ELIDE_UNLOCK_ADAPTIVE() will adapt the eli- sion behavior associated with lock operations according to the run-time be- havior of the program. This behavior is defined by the ck_elide_config structure pointer passed to CK_ELIDE_LOCK_ADAPTIVE(). A thread-local ck_elide_stat structure must be passed to both CK_ELIDE_LOCK_ADAPTIVE() and CK_ELIDE_UNLOCK_ADAPTIVE(). This structure is expected to be unique for different workloads, may not be re-used in recursive acquisitions and must match the lifetime of the lock it is associated with. It is safe to mix adaptive calls with best-effort calls. Both ck_spinlock.h and ck_rwlock.h define ck_elide wrappers under the ck_spinlock and ck_rwlock namespace, respectively. EXAMPLES This example utilizes built-in lock elision facilities in ck_rwlock and ck_spinlock. #include <ck_rwlock.h> #include <ck_spinlock.h> static ck_rwlock_t rw = CK_RWLOCK_INITIALIZER; static struct ck_elide_config rw_config = CK_ELIDE_CONFIG_DEFAULT_INITIALIZER; static __thread ck_elide_stat_t rw_stat = CK_ELIDE_STAT_INITIALIZER; static ck_spinlock_t spinlock = CK_SPINLOCK_INITIALIZER; static struct ck_elide_config spinlock_config = CK_ELIDE_CONFIG_DEFAULT_INITIALIZER; static __thread ck_elide_stat_t spinlock_stat = CK_ELIDE_STAT_INITIALIZER; void function(void) { /* Lock-unlock write-side lock in weak best-effort manner. */ CK_ELIDE_LOCK(ck_rwlock_write, &rw); CK_ELIDE_UNLOCK(ck_rwlock_write, &rw); /* Attempt to acquire the write-side lock. */ if (CK_ELIDE_TRYLOCK(ck_rwlock_write, &rw) == true) CK_ELIDE_UNLOCK(ck_rwlock_write, &rw); /* Lock-unlock read-side lock in weak best-effort manner. */ CK_ELIDE_LOCK(ck_rwlock_read, &rw); CK_ELIDE_UNLOCK(ck_rwlock_read, &rw); /* Attempt to acquire the read-side lock. */ if (CK_ELIDE_TRYLOCK(ck_rwlock_read, &rw) == true) CK_ELIDE_UNLOCK(ck_rwlock_read, &rw); /* Lock-unlock write-side lock in an adaptive manner. */ CK_ELIDE_LOCK_ADAPTIVE(ck_rwlock_write, &rw_stat, &rw_config, &rw); CK_ELIDE_UNLOCK_ADAPTIVE(ck_rwlock_write, &rw_stat, &rw_config, &rw); /* Lock-unlock read-side lock in an adaptive manner. */ CK_ELIDE_LOCK_ADAPTIVE(ck_rwlock_read, &rw_stat, &rw_config, &rw); CK_ELIDE_UNLOCK_ADAPTIVE(ck_rwlock_read, &rw_stat, &rw_config, &rw); /* Lock-unlock spinlock in weak best-effort manner. */ CK_ELIDE_LOCK(ck_spinlock, &spinlock); CK_ELIDE_UNLOCK(ck_spinlock, &spinlock); /* Attempt to acquire the lock. */ if (CK_ELIDE_TRYLOCK(ck_spinlock, &lock) == true) CK_ELIDE_UNLOCK(ck_spinlock, &spinlock); /* Lock-unlock spinlock in an adaptive manner. */ CK_ELIDE_LOCK_ADAPTIVE(ck_spinlock, &spinlock_stat, &spinlock_config, &spinlock); CK_ELIDE_UNLOCK_ADAPTIVE(ck_spinlock, &spinlock_stat, &spinlock_config, &spinlock); } In this example, user-defined locking functions are provided an elision im- plementation. /* Assume lock_t has been previously defined. */ #include <ck_elide.h> /* * This function returns true if the lock is unavailable at the time * it was called or false if the lock is available. */ bool is_locked(lock_t *); /* * This function acquires the supplied lock. */ void lock(lock_t *); /* * This function releases the lock. */ void unlock(lock_t *); CK_ELIDE_PROTOTYPE(my_lock, lock_t, is_locked, lock, is_locked, unlock) static lock_t lock; void function(void) { CK_ELIDE_LOCK(my_lock, &lock); CK_ELIDE_UNLOCK(my_lock, &lock); } SEE ALSO ck_rwlock(3), ck_spinlock(3) Ravi Rajwar and James R. Goodman. 2001. Speculative lock elision: enabling highly concurrent multithreaded execution. In Proceedings of the 34th an- nual ACM/IEEE international symposium on Microarchitecture (MICRO 34). IEEE Computer Society, Washington, DC, USA, 294-305. Additional information available at http://en.wikipedia.org/wiki/Transac- tional_Synchronization_Extensions and http://concurrencykit.org/ July 13, 2013. ck_elide(3)
NAME | LIBRARY | SYNOPSIS | DESCRIPTION | EXAMPLES | SEE ALSO
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