io-threads: Allow scaling to be switched off

The default is also to provide no scaling. For both, ordered and
unordered request pools, when scaling is off, we maintain atleast the
minimum number of threads specified in the volfile.

Signed-off-by: Anand V. Avati <avati@amp.gluster.com>

1 files changed, 55 insertions, 10 deletions

diff --git a/xlators/performance/io-threads/src/io-threads.c b/xlators/performance/io-threads/src/io-threads.c
index 1d255d972..fbd002267 100644
--- a/xlators/performance/io-threads/src/io-threads.c
+++ b/xlators/performance/io-threads/src/io-threads.c
@@ -41,6 +41,30 @@ void iot_startup_workers (iot_worker_t **workers, int start_idx, int count,
 void * iot_worker_unordered (void *arg);
 void * iot_worker_ordered (void *arg);
 
+int
+iot_unordered_request_balancer (iot_conf_t *conf)
+{
+        long int        rand = 0;
+        int             idx = 0;
+
+        /* Decide which thread will service the request.
+         * FIXME: This should change into some form of load-balancing.
+         * */
+        rand = random ();
+
+        /* If scaling is on, we can choose from any thread
+        * that has been allocated upto, max_o_threads, but
+        * with scaling off, we'll never have threads more
+        * than min_o_threads.
+        */
+        if (iot_unordered_scaling_on (conf))
+                idx = (rand % conf->max_u_threads);
+        else
+                idx = (rand % conf->min_u_threads);
+
+        return idx;
+}
+
 void
 iot_schedule_unordered (iot_conf_t *conf,
                 inode_t *inode,
@@ -50,10 +74,7 @@ iot_schedule_unordered (iot_conf_t *conf,
         iot_worker_t    *selected_worker = NULL;
         iot_request_t   *req = NULL;
 
-        /* First decide which thread will service the request.
-         * FIXME: This should change into some form of load-balancing.
-         * */
-        idx = (random() % conf->max_u_threads);
+        idx = iot_unordered_request_balancer (conf);
         selected_worker = conf->uworkers[idx];
 
         req = iot_init_request (stub);
@@ -73,6 +94,33 @@ iot_schedule_unordered (iot_conf_t *conf,
         pthread_mutex_unlock (&selected_worker->qlock);
 }
 
+/* Assumes inode lock is held. */
+int
+iot_ordered_request_balancer (iot_conf_t *conf,
+                inode_t *inode)
+{
+        int             ctxret = 0;
+        long int        rand = 0;
+        uint64_t        idx = 0;
+
+        ctxret = __inode_ctx_get (inode, conf->this, &idx);
+        if (ctxret < 0) {
+                rand = random ();
+                /* If scaling is on, we can choose from any thread
+                 * that has been allocated upto, max_o_threads, but
+                 * with scaling off, we'll never have threads more
+                 * than min_o_threads.
+                 */
+                if (iot_ordered_scaling_on (conf))
+                        idx = (rand % conf->max_o_threads);
+                else
+                        idx = (rand % conf->min_o_threads);
+                __inode_ctx_put (inode, conf->this, idx);
+        }
+
+        return idx;
+}
+
 void
 iot_schedule_ordered (iot_conf_t *conf,
                 inode_t *inode,
@@ -81,7 +129,6 @@ iot_schedule_ordered (iot_conf_t *conf,
         uint64_t        idx = 0;
         iot_worker_t    *selected_worker = NULL;
         iot_request_t   * req = NULL;
-        int             ctxret = 0;
 
         if (inode == NULL) {
                 gf_log (conf->this->name, GF_LOG_ERROR,
@@ -91,11 +138,7 @@ iot_schedule_ordered (iot_conf_t *conf,
         req = iot_init_request (stub);
         LOCK (&inode->lock);
         {
-                ctxret = __inode_ctx_get (inode, conf->this, &idx);
-                if (ctxret < 0) {
-                        idx = (random () % conf->max_o_threads);
-                        __inode_ctx_put (inode, conf->this, idx);
-                }
+                idx = iot_ordered_request_balancer (conf, inode);
                 /* inode lock once acquired, cannot be left here
                  * because other gluster main threads might be
                  * contending on it to append a request for this file.
@@ -1762,12 +1805,14 @@ init (xlator_t *this)
         conf->max_u_threads = IOT_MAX_THREADS;
         conf->min_u_threads = IOT_MIN_THREADS;
         conf->u_idle_time = IOT_DEFAULT_IDLE;
+        conf->u_scaling = IOT_SCALING_OFF;
 
         /* Init params for ordered workers. */
         pthread_mutex_init (&conf->otlock, NULL);
         conf->max_o_threads = IOT_MAX_THREADS;
         conf->min_o_threads = IOT_MIN_THREADS;
         conf->o_idle_time = IOT_DEFAULT_IDLE;
+        conf->o_scaling = IOT_SCALING_OFF;
 
         conf->this = this;
 	workers_init (conf);