NAME¶
ck_cohort
—
generalized interface for lock cohorts
LIBRARY¶
Concurrency Kit (libck, -lck)
SYNOPSIS¶
#include
<ck_cohort.h>
CK_COHORT_PROTOTYPE
(
COHORT_NAME
cohort_name,
LOCK_FXN
global_lock_method,
LOCK_FXN
global_unlock_method,
LOCK_FXN
local_lock_method,
LOCK_FXN
local_unlock_method);
CK_COHORT_TRYLOCK_PROTOTYPE
(
COHORT_NAME
cohort_name,
LOCK_FXN
global_lock_method,
LOCK_FXN
global_unlock_method,
BOOL_LOCK_FXN
global_locked_method,
BOOL_LOCK_FXN
global_trylock_method,
LOCK_FXN
local_lock_method,
LOCK_FXN
local_unlock_method,
BOOL_LOCK_FXN
local_locked_method,
BOOL_LOCK_FXN
local_trylock_method);
CK_COHORT_INSTANCE
(
COHORT_NAME
cohort_name);
CK_COHORT_INIT
(
COHORT_NAME
cohort_name,
ck_cohort
*cohort,
void
*global_lock,
void
*local_lock,
unsigned int
pass_limit);
CK_COHORT_LOCK
(
COHORT_NAME
cohort_name,
ck_cohort
*cohort,
void
*global_context,
void
*local_context);
CK_COHORT_UNLOCK
(
COHORT_NAME
cohort_name,
ck_cohort
*cohort,
void
*global_context,
void
*local_context);
Where LOCK_FXN refers to a method with the signature
void(void *lock, void *context)
BOOL_LOCK_FXN refers to a method with the signature
bool(void *lock, void *context)
The
context argument in each signature is used
to pass along any additional information that the lock might need for its
lock, unlock and trylock methods. The values for this argument are provided to
each call to
CK_COHORT_LOCK(3),
CK_COHORT_UNLOCK(3),
CK_COHORT_LOCKED(3), and
CK_COHORT_TRYLOCK(3)
DESCRIPTION¶
ck_cohort.h provides an interface for defining lock cohorts with arbitrary lock
types. Cohorts are a mechanism for coordinating threads on NUMA architectures
in order to reduce the frequency with which a lock is passed between threads
on different clusters.
Before using a cohort, the user must define a cohort type using either the
CK_COHORT_PROTOTYPE
() or the
CK_COHORT_TRYLOCK_PROTOTYPE
() macros. These
macros allow the user to specify the lock methods that they would like the
cohort to use. See the
CK_COHORT_PROTOTYPE(3) and
CK_COHORT_TRYLOCK_PROTOTYPE(3) man pages for more
details.
EXAMPLE¶
#include <stdlib.h>
#include <pthread.h>
#include <ck_pr.h>
#include <ck_cohort.h>
#include <ck_spinlock.h>
/*
* Create cohort methods with signatures that match
* the required signature
*/
static void
ck_spinlock_lock_with_context(ck_spinlock_t *lock, void *context)
{
(void)context;
ck_spinlock_lock(lock);
return;
}
static void
ck_spinlock_unlock_with_context(ck_spinlock_t *lock, void *context)
{
(void)context;
ck_spinlock_unlock(lock);
return;
}
static bool
ck_spinlock_locked_with_context(ck_spinlock_t *lock, void *context)
{
(void)context;
return ck_spinlock_locked(lock);
}
/*
* define a cohort type named "test_cohort" that will use
* the above methods for both its global and local locks
*/
CK_COHORT_PROTOTYPE(test_cohort,
ck_spinlock_lock_with_context, ck_spinlock_unlock_with_context, ck_spinlock_locked_with_context,
ck_spinlock_lock_with_context, ck_spinlock_unlock_with_context, ck_spinlock_locked_with_context)
static ck_spinlock_t global_lock = CK_SPINLOCK_INITIALIZER;
static unsigned int ready;
static void *
function(void *context)
{
CK_COHORT_INSTANCE(test_cohort) *cohort = context;
while (ready == 0);
while (ready > 0) {
/*
* acquire the cohort lock before performing critical section.
* note that we pass NULL for both the global and local context
* arguments because neither the lock nor unlock functions
* will use them.
*/
CK_COHORT_LOCK(test_cohort, cohort, NULL, NULL);
/* perform critical section */
/* relinquish cohort lock */
CK_COHORT_UNLOCK(test_cohort, cohort, NULL, NULL);
}
return NULL;
}
int
main(void)
{
unsigned int nthr = 4;
unsigned int n_cohorts = 2;
unsigned int i;
/* allocate 2 cohorts of the defined type */
CK_COHORT_INSTANCE(test_cohort) *cohorts =
calloc(n_cohorts, sizeof(CK_COHORT_INSTANCE(test_cohort)));
/* create local locks to use with each cohort */
ck_spinlock_t *local_locks =
calloc(n_cohorts, sizeof(ck_spinlock_t));
pthread_t *threads =
calloc(nthr, sizeof(pthread_t));
/* initialize each of the cohorts before using them */
for (i = 0 ; i < n_cohorts ; ++i) {
CK_COHORT_INIT(test_cohort, cohorts + i, &global_lock, local_locks + i,
CK_COHORT_DEFAULT_LOCAL_PASS_LIMIT);
}
/* start each thread and assign cohorts equally */
for (i = 0 ; i < nthr ; ++i) {
pthread_create(threads + i, NULL, function, cohorts + (i % n_cohorts));
}
ck_pr_store_uint(&ready, 1);
sleep(10);
ck_pr_store_uint(&ready, 0);
for (i = 0 ; i < nthr ; ++i) {
pthread_join(threads[i], NULL);
}
return 0;
}
SEE ALSO¶
CK_COHORT_PROTOTYPE(3),
CK_COHORT_TRYLOCK_PROTOTYPE(3),
CK_COHORT_INSTANCE(3),
CK_COHORT_INITIALIZER(3),
CK_COHORT_INIT(3),
CK_COHORT_LOCK(3),
CK_COHORT_UNLOCK(3),
CK_COHORT_LOCKED(3),
CK_COHORT_TRYLOCK(3),
Additional information available at
http://concurrencykit.org/