randws.c

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/* -*- Mode: C; c-basic-offset:4 ; indent-tabs-mode:nil ; -*- */
/*
 * See COPYRIGHT in top-level directory.
 */
 
#include "abti.h"
 
/* Random Work-stealing Scheduler Implementation */
 
static int sched_init(ABT_sched sched, ABT_sched_config config);
static void sched_run(ABT_sched sched);
static int sched_free(ABT_sched);
 
static ABT_sched_def sched_randws_def = {
    .type = ABT_SCHED_TYPE_ULT,
    .init = sched_init,
    .run = sched_run,
    .free = sched_free,
    .get_migr_pool = NULL,
};
 
typedef struct {
    uint32_t event_freq;
    int num_pools;
    ABT_pool *pools;
#ifdef ABT_CONFIG_USE_SCHED_SLEEP
    struct timespec sleep_time;
#endif
} sched_data;
 
ABT_sched_def *ABTI_sched_get_randws_def(void)
{
    return &sched_randws_def;
}
 
static int sched_init(ABT_sched sched, ABT_sched_config config)
{
    int abt_errno;
    int num_pools;
    ABTI_global *p_global = ABTI_global_get_global();
 
    ABTI_sched *p_sched = ABTI_sched_get_ptr(sched);
    ABTI_CHECK_NULL_SCHED_PTR(p_sched);
    ABTI_sched_config *p_config = ABTI_sched_config_get_ptr(config);
 
    /* Default settings */
    sched_data *p_data;
    abt_errno = ABTU_malloc(sizeof(sched_data), (void **)&p_data);
    ABTI_CHECK_ERROR(abt_errno);
#ifdef ABT_CONFIG_USE_SCHED_SLEEP
    p_data->sleep_time.tv_sec = 0;
    p_data->sleep_time.tv_nsec = p_global->sched_sleep_nsec;
#endif
 
    /* Set the default value by default. */
    p_data->event_freq = p_global->sched_event_freq;
    if (p_config) {
        int event_freq;
        /* Set the variables from config */
        abt_errno = ABTI_sched_config_read(p_config, ABT_sched_basic_freq.idx,
                                           &event_freq);
        if (abt_errno == ABT_SUCCESS) {
            p_data->event_freq = event_freq;
        }
    }
 
    /* Save the list of pools */
    num_pools = p_sched->num_pools;
    p_data->num_pools = num_pools;
    abt_errno =
        ABTU_malloc(num_pools * sizeof(ABT_pool), (void **)&p_data->pools);
    if (ABTI_IS_ERROR_CHECK_ENABLED && abt_errno != ABT_SUCCESS) {
        ABTU_free(p_data);
        ABTI_HANDLE_ERROR(abt_errno);
    }
    memcpy(p_data->pools, p_sched->pools, sizeof(ABT_pool) * num_pools);
 
    p_sched->data = p_data;
    return ABT_SUCCESS;
}
 
static void sched_run(ABT_sched sched)
{
    ABTI_global *p_global = ABTI_global_get_global();
    ABTI_xstream *p_local_xstream =
        ABTI_local_get_xstream(ABTI_local_get_local());
    uint32_t work_count = 0;
    sched_data *p_data;
    int num_pools;
    ABT_pool *pools;
    int target;
    unsigned seed = time(NULL);
    CNT_DECL(run_cnt);
 
    ABTI_sched *p_sched = ABTI_sched_get_ptr(sched);
    ABTI_ASSERT(p_sched);
 
    p_data = (sched_data *)p_sched->data;
    num_pools = p_sched->num_pools;
    pools = p_data->pools;
 
    while (1) {
        CNT_INIT(run_cnt, 0);
 
        /* Execute one work unit from the scheduler's pool */
        ABT_pool pool = pools[0];
        ABTI_pool *p_pool = ABTI_pool_get_ptr(pool);
        ABT_thread thread =
            ABTI_pool_pop(p_pool, ABT_POOL_CONTEXT_OWNER_PRIMARY);
        if (thread != ABT_THREAD_NULL) {
            ABTI_thread *p_thread = ABTI_thread_get_ptr(thread);
            ABTI_ythread_schedule(p_global, &p_local_xstream, p_thread);
            CNT_INC(run_cnt);
        } else if (num_pools > 1) {
            /* Steal a work unit from other pools */
            target =
                (num_pools == 2) ? 1 : (rand_r(&seed) % (num_pools - 1) + 1);
            pool = pools[target];
            p_pool = ABTI_pool_get_ptr(pool);
            thread = ABTI_pool_pop(p_pool, ABT_POOL_CONTEXT_OWNER_SECONDARY);
            if (thread != ABT_THREAD_NULL) {
                ABTI_thread *p_thread = ABTI_thread_get_ptr(thread);
                ABTI_ythread_schedule(p_global, &p_local_xstream, p_thread);
                CNT_INC(run_cnt);
            }
        }
 
        if (++work_count >= p_data->event_freq) {
            ABTI_xstream_check_events(p_local_xstream, p_sched);
            if (ABTI_sched_has_to_stop(p_sched) == ABT_TRUE)
                break;
            work_count = 0;
            SCHED_SLEEP(run_cnt, p_data->sleep_time);
        }
    }
}
 
static int sched_free(ABT_sched sched)
{
    ABTI_sched *p_sched = ABTI_sched_get_ptr(sched);
    ABTI_ASSERT(p_sched);
 
    sched_data *p_data = (sched_data *)p_sched->data;
    ABTU_free(p_data->pools);
    ABTU_free(p_data);
    return ABT_SUCCESS;
}