From: Dave <dglen@micron.com>
Date: Thu, 16 Jul 2015 20:56:00 +0000 (-0600)
Subject: Re-seed random generator correctly between loops
X-Git-Tag: fio-2.2.10~35
X-Git-Url: https://git.kernel.dk/?p=fio.git;a=commitdiff_plain;h=1520f26e713a2fded6728ad372af0d7b8c197adf

Re-seed random generator correctly between loops

re-seeding random generator in this way means that random patterns will
precisely repeat between iterations.  if rand_repeatable is set, this is
desirable, otherwise it may produce unexpected IO patterns in random IO
testing.

Signed-off-by: Jens Axboe <axboe@fb.com>
---

diff --git a/libfio.c b/libfio.c
index 3a28f55e..30a3acb5 100644
--- a/libfio.c
+++ b/libfio.c
@@ -116,9 +116,10 @@ void clear_io_state(struct thread_data *td)
 	}
 
 	/*
-	 * Set the same seed to get repeatable runs
+	 * Re-Seed random number generator if rand_repeatable is true
 	 */
-	td_fill_rand_seeds(td);
+	if (td->o.rand_repeatable)
+		td_fill_rand_seeds(td);
 }
 
 void reset_all_stats(struct thread_data *td)