From 5bfc35d7abe2582dc54127ca1d6e03792c9d62f5 Mon Sep 17 00:00:00 2001
From: Jens Axboe <jens.axboe@oracle.com>
Date: Tue, 7 Apr 2009 13:28:12 +0200
Subject: [PATCH] Reseed random generator for loop/time based runs

Then we get repeatable 2nd/3rd/etc runs. This is important
if the file layout was random, otherwise subsequent runs will
get very different results.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
---
 fio.c  |  5 +++++
 fio.h  |  3 +++
 init.c | 42 +++++++++++++++++++++++-------------------
 io_u.c | 11 -----------
 4 files changed, 31 insertions(+), 30 deletions(-)

diff --git a/fio.c b/fio.c
index f699951d..ad2282d7 100644
--- a/fio.c
+++ b/fio.c
@@ -876,6 +876,11 @@ static void reset_io_counters(struct thread_data *td)
 	 */
 	if (td->o.time_based || td->o.loops)
 		td->nr_done_files = 0;
+
+	/*
+	 * Set the same seed to get repeatable runs
+	 */
+	td_fill_rand_seeds(td);
 }
 
 void reset_all_stats(struct thread_data *td)
diff --git a/fio.h b/fio.h
index 4077a5be..ff0068ca 100644
--- a/fio.h
+++ b/fio.h
@@ -572,6 +572,8 @@ struct thread_data {
 
 	char *sysfs_root;
 
+	unsigned long rand_seeds[6];
+
 	os_random_state_t bsrange_state;
 	os_random_state_t verify_state;
 
@@ -854,6 +856,7 @@ extern int fio_show_option_help(const char *);
 extern void fio_options_dup_and_init(struct option *);
 extern void options_mem_dupe(struct thread_data *);
 extern void options_mem_free(struct thread_data *);
+extern void td_fill_rand_seeds(struct thread_data *);
 #define FIO_GETOPT_JOB		0x89988998
 #define FIO_NR_OPTIONS		128
 
diff --git a/init.c b/init.c
index 80d098dd..8deedcc6 100644
--- a/init.c
+++ b/init.c
@@ -408,13 +408,32 @@ static int exists_and_not_file(const char *filename)
 	return 1;
 }
 
+void td_fill_rand_seeds(struct thread_data *td)
+{
+	os_random_seed(td->rand_seeds[0], &td->bsrange_state);
+	os_random_seed(td->rand_seeds[1], &td->verify_state);
+	os_random_seed(td->rand_seeds[2], &td->rwmix_state);
+
+	if (td->o.file_service_type == FIO_FSERVICE_RANDOM)
+		os_random_seed(td->rand_seeds[3], &td->next_file_state);
+
+	os_random_seed(td->rand_seeds[5], &td->file_size_state);
+
+	if (!td_random(td))
+		return;
+
+	if (td->o.rand_repeatable)
+		td->rand_seeds[4] = FIO_RANDSEED * td->thread_number;
+
+	os_random_seed(td->rand_seeds[4], &td->random_state);
+}
+
 /*
  * Initialize the various random states we need (random io, block size ranges,
  * read/write mix, etc).
  */
 static int init_random_state(struct thread_data *td)
 {
-	unsigned long seeds[6];
 	int fd;
 
 	fd = open("/dev/urandom", O_RDONLY);
@@ -423,30 +442,15 @@ static int init_random_state(struct thread_data *td)
 		return 1;
 	}
 
-	if (read(fd, seeds, sizeof(seeds)) < (int) sizeof(seeds)) {
+	if (read(fd, td->rand_seeds, sizeof(td->rand_seeds)) <
+	    (int) sizeof(td->rand_seeds)) {
 		td_verror(td, EIO, "read");
 		close(fd);
 		return 1;
 	}
 
 	close(fd);
-
-	os_random_seed(seeds[0], &td->bsrange_state);
-	os_random_seed(seeds[1], &td->verify_state);
-	os_random_seed(seeds[2], &td->rwmix_state);
-
-	if (td->o.file_service_type == FIO_FSERVICE_RANDOM)
-		os_random_seed(seeds[3], &td->next_file_state);
-
-	os_random_seed(seeds[5], &td->file_size_state);
-
-	if (!td_random(td))
-		return 0;
-
-	if (td->o.rand_repeatable)
-		seeds[4] = FIO_RANDSEED * td->thread_number;
-
-	os_random_seed(seeds[4], &td->random_state);
+	td_fill_rand_seeds(td);
 	return 0;
 }
 
diff --git a/io_u.c b/io_u.c
index 476658ed..71089390 100644
--- a/io_u.c
+++ b/io_u.c
@@ -748,23 +748,12 @@ static int set_io_u_file(struct thread_data *td, struct io_u *io_u)
 		if (!f)
 			return 1;
 
-set_file:
 		io_u->file = f;
 		get_file(f);
 
 		if (!fill_io_u(td, io_u))
 			break;
 
-		/*
-		 * optimization to prevent close/open of the same file. This
-		 * way we preserve queueing etc.
-		 */
-		if (td->o.nr_files == 1 && td->o.time_based) {
-			put_file_log(td, f);
-			fio_file_reset(f);
-			goto set_file;
-		}
-
 		put_file_log(td, f);
 		td_io_close_file(td, f);
 		io_u->file = NULL;
-- 
2.25.1