From 01eed4db668dd7b009ff5c120ef7146812cef606 Mon Sep 17 00:00:00 2001
From: Alexey Kopytov <akopytov@gmail.com>
Date: Tue, 4 Jul 2017 11:21:21 +0300
Subject: [PATCH] Remove busy-wait in --rate mode to avoid CPU hogging.

In the bounded rate (--rate) mode, if the queue is empty, sleep for a
certain amount of time depending on the requested rate and the number of
worker threads instead of spinning on the queue.

Clean up some code duplication by removing sb_next_event().
---
 src/sysbench.c | 43 ++-----------------------------------------
 1 file changed, 2 insertions(+), 41 deletions(-)

diff --git a/src/sysbench.c b/src/sysbench.c
index ab5549d..a4712d0 100644
--- a/src/sysbench.c
+++ b/src/sysbench.c
@@ -703,7 +703,7 @@ bool sb_more_events(int thread_id)
 
     while (!ck_ring_dequeue_spmc(&queue_ring, queue_ring_buffer, &ptr) &&
            !ck_pr_load_int(&queue_is_full))
-      ck_pr_stall();
+      usleep(500000.0 * sb_globals.threads / sb_globals.tx_rate);
 
     if (ck_pr_load_int(&queue_is_full))
     {
@@ -721,45 +721,6 @@ bool sb_more_events(int thread_id)
   return true;
 }
 
-/*
-   Get the next event, or return an 'empty' event with type = SB_REQ_TYPE_NULL,
-   if there are no more events to execute.
-*/
-
-sb_event_t sb_next_event(sb_test_t *test, int thread_id)
-{
-  uint64_t            queue_start_time = 0;
-
-  /* If we are in tx_rate mode, we take events from queue */
-  if (sb_globals.tx_rate > 0)
-  {
-    void *ptr = NULL;
-
-    while (!ck_ring_dequeue_spmc(&queue_ring, queue_ring_buffer, &ptr) &&
-           !ck_pr_load_int(&queue_is_full))
-      ck_pr_stall();
-
-    if (ck_pr_load_int(&queue_is_full))
-    {
-      log_text(LOG_FATAL, "Event queue is full. Terminating the worker thread");
-
-      sb_event_t          event;
-      event.type = SB_REQ_TYPE_NULL;
-
-      return event;
-    }
-
-    queue_start_time = ((uint64_t *) ptr)[0];
-
-    ck_pr_inc_int(&sb_globals.concurrency);
-
-    timers[thread_id].queue_time = sb_timer_value(&sb_exec_timer) -
-      queue_start_time;
-  }
-
-  return test->ops.next_event(thread_id);
-}
-
 
 void sb_event_start(int thread_id)
 {
@@ -796,7 +757,7 @@ static int thread_run(sb_test_t *test, int thread_id)
 
   while (sb_more_events(thread_id) && rc == 0)
   {
-    event = sb_next_event(test, thread_id);
+    event = test->ops.next_event(thread_id);
     if (event.type == SB_REQ_TYPE_NULL)
       break;