From 61e7f1939ada762d6134e0777c38997593e93ff2 Mon Sep 17 00:00:00 2001
From: Pedro Gonnet <pedro.gonnet@durham.ac.uk>
Date: Sat, 22 Jun 2013 11:11:20 +0000
Subject: [PATCH] implement strategy to sleep if tasks are rare.
Former-commit-id: 544f802833b16e3ecf9e399e2f8a4d02579ef817
---
src/scheduler.c | 15 +++++++++++++++
src/scheduler.h | 4 ++++
2 files changed, 19 insertions(+)
diff --git a/src/scheduler.c b/src/scheduler.c
index 8ffc16a480..a100d55039 100644
--- a/src/scheduler.c
+++ b/src/scheduler.c
@@ -25,6 +25,7 @@
#include <stdlib.h>
#include <string.h>
#include <math.h>
+#include <pthread.h>
/* Local headers. */
#include "error.h"
@@ -627,7 +628,10 @@ void scheduler_done ( struct scheduler *s , struct task *t ) {
}
/* Task definitely done. */
+ pthread_mutex_lock( &s->sleep_mutex );
atomic_dec( &s->waiting );
+ pthread_cond_broadcast( &s->sleep_cond );
+ pthread_mutex_unlock( &s->sleep_mutex );
}
@@ -664,6 +668,12 @@ struct task *scheduler_gettask ( struct scheduler *s , int qid ) {
if ( max_count > 0 && ( res = queue_gettask( &s->queues[ max_ind ] , qid , 0 ) ) != NULL )
return res;
}
+
+ /* If we failed, take a short nap. */
+ pthread_mutex_lock( &s->sleep_mutex );
+ if ( s->waiting > 0 )
+ pthread_cond_wait( &s->sleep_cond , &s->sleep_mutex );
+ pthread_mutex_unlock( &s->sleep_mutex );
}
@@ -696,6 +706,11 @@ void scheduler_init ( struct scheduler *s , struct space *space , int nr_queues
for ( k = 0 ; k < nr_queues ; k++ )
queue_init( &s->queues[k] , NULL );
+ /* Init the sleep mutex and cond. */
+ if ( pthread_cond_init( &s->sleep_cond , NULL ) != 0 ||
+ pthread_mutex_init( &s->sleep_mutex , NULL ) != 0 )
+ error( "Failed to initialize sleep barrier." );
+
/* Set the scheduler variables. */
s->nr_queues = nr_queues;
s->flags = flags;
diff --git a/src/scheduler.h b/src/scheduler.h
index 485c9b101b..f38929d72e 100644
--- a/src/scheduler.h
+++ b/src/scheduler.h
@@ -56,6 +56,10 @@ struct scheduler {
/* Lock for this scheduler. */
lock_type lock;
+ /* Waiting queue. */
+ pthread_mutex_t sleep_mutex;
+ pthread_cond_t sleep_cond;
+
/* The space associated with this scheduler. */
struct space *space;
--
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