ck_elide(3) | Library Functions Manual | ck_elide(3) |
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 acquisition, 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-effects of the critical section and force every thread to retry the lock acquisition 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 executed. 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
UNLOCK_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 operation 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 elision behavior associated with lock operations according to
the run-time behavior 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 implementation.
/* 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
Ravi Rajwar and James R. Goodman. 2001. Speculative lock elision: enabling highly concurrent multithreaded execution. In Proceedings of the 34th annual 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/Transactional_Synchronization_Extensions and http://concurrencykit.org/
July 13, 2013. |