From: Jens Axboe <axboe@kernel.dk>
Date: Sat, 11 Jan 2014 03:57:01 +0000 (-0700)
Subject: Add option to manually seed the random generators
X-Git-Tag: fio-2.1.5~40
X-Git-Url: https://git.kernel.dk/?p=fio.git;a=commitdiff_plain;h=04778baf2def8c1c5a3d7d60233c56d140831711

Add option to manually seed the random generators

Signed-off-by: Jens Axboe <axboe@kernel.dk>
---

diff --git a/HOWTO b/HOWTO
index 044b5722..2183be10 100644
--- a/HOWTO
+++ b/HOWTO
@@ -384,6 +384,11 @@ unified_rw_reporting=bool	Fio normally reports statistics on a per
 randrepeat=bool	For random IO workloads, seed the generator in a predictable
 		way so that results are repeatable across repetitions.
 
+randseed=int	Seed the random number generators based on this seed value, to
+		be able to control what sequence of output is being generated.
+		If not set, the random sequence depends on the randrepeat
+		setting.
+
 use_os_rand=bool Fio can either use the random generator supplied by the OS
 		to generator random offsets, or it can use it's own internal
 		generator (based on Tausworthe). Default is to use the
diff --git a/cconv.c b/cconv.c
index dd61d103..3a6880ac 100644
--- a/cconv.c
+++ b/cconv.c
@@ -118,6 +118,7 @@ void convert_thread_options_to_cpu(struct thread_options *o,
 	o->do_disk_util = le32_to_cpu(top->do_disk_util);
 	o->override_sync = le32_to_cpu(top->override_sync);
 	o->rand_repeatable = le32_to_cpu(top->rand_repeatable);
+	o->rand_seed = le32_to_cpu(top->rand_seed);
 	o->use_os_rand = le32_to_cpu(top->use_os_rand);
 	o->log_avg_msec = le32_to_cpu(top->log_avg_msec);
 	o->norandommap = le32_to_cpu(top->norandommap);
@@ -282,6 +283,7 @@ void convert_thread_options_to_net(struct thread_options_pack *top,
 	top->do_disk_util = cpu_to_le32(o->do_disk_util);
 	top->override_sync = cpu_to_le32(o->override_sync);
 	top->rand_repeatable = cpu_to_le32(o->rand_repeatable);
+	top->rand_seed = cpu_to_le32(o->rand_seed);
 	top->use_os_rand = cpu_to_le32(o->use_os_rand);
 	top->log_avg_msec = cpu_to_le32(o->log_avg_msec);
 	top->norandommap = cpu_to_le32(o->norandommap);
diff --git a/fio.1 b/fio.1
index 9ee0eef1..6c3dd21b 100644
--- a/fio.1
+++ b/fio.1
@@ -288,6 +288,11 @@ set, the fio will sum the results and report them as "mixed" instead.
 Seed the random number generator in a predictable way so results are repeatable
 across runs.  Default: true.
 .TP
+.BI randseed \fR=\fPint
+Seed the random number generators based on this seed value, to be able to
+control what sequence of output is being generated. If not set, the random
+sequence depends on the \fBrandrepeat\fR setting.
+.TP
 .BI use_os_rand \fR=\fPbool
 Fio can either use the random generator supplied by the OS to generator random
 offsets, or it can use it's own internal generator (based on Tausworthe).
diff --git a/init.c b/init.c
index ba22f785..af0bb2db 100644
--- a/init.c
+++ b/init.c
@@ -635,6 +635,12 @@ static int fixup_options(struct thread_data *td)
 	if (td->o.oatomic)
 		td->o.odirect = 1;
 
+	/*
+	 * If randseed is set, that overrides randrepeat
+	 */
+	if (td->o.rand_seed)
+		td->o.rand_repeatable = 0;
+
 	return ret;
 }
 
@@ -830,10 +836,15 @@ static int setup_random_seeds(struct thread_data *td)
 	unsigned long seed;
 	unsigned int i;
 
-	if (!td->o.rand_repeatable)
+	if (!td->o.rand_repeatable && !td->o.rand_seed)
 		return init_random_state(td, td->rand_seeds, sizeof(td->rand_seeds));
 
-	for (seed = 0x89, i = 0; i < 4; i++)
+	if (!td->o.rand_seed)
+		seed = 0x89;
+	else
+		seed = td->o.rand_seed;
+
+	for (i = 0; i < 4; i++)
 		seed *= 0x9e370001UL;
 
 	for (i = 0; i < FIO_RAND_NR_OFFS; i++) {
diff --git a/options.c b/options.c
index b0f45098..16b66369 100644
--- a/options.c
+++ b/options.c
@@ -1626,6 +1626,16 @@ struct fio_option fio_options[FIO_MAX_OPTS] = {
 		.category = FIO_OPT_C_IO,
 		.group	= FIO_OPT_G_RANDOM,
 	},
+	{
+		.name	= "randseed",
+		.lname	= "The random generator seed",
+		.type	= FIO_OPT_INT,
+		.off1	= td_var_offset(rand_seed),
+		.help	= "Set the random generator seed value",
+		.parent = "rw",
+		.category = FIO_OPT_C_IO,
+		.group	= FIO_OPT_G_RANDOM,
+	},
 	{
 		.name	= "use_os_rand",
 		.lname	= "Use OS random",
diff --git a/server.h b/server.h
index 84901cf6..0416fd7d 100644
--- a/server.h
+++ b/server.h
@@ -38,7 +38,7 @@ struct fio_net_cmd_reply {
 };
 
 enum {
-	FIO_SERVER_VER			= 28,
+	FIO_SERVER_VER			= 29,
 
 	FIO_SERVER_MAX_FRAGMENT_PDU	= 1024,
 
diff --git a/thread_options.h b/thread_options.h
index 7476d8c2..e2c6e885 100644
--- a/thread_options.h
+++ b/thread_options.h
@@ -100,6 +100,7 @@ struct thread_options {
 	unsigned int do_disk_util;
 	unsigned int override_sync;
 	unsigned int rand_repeatable;
+	unsigned int rand_seed;
 	unsigned int use_os_rand;
 	unsigned int log_avg_msec;
 	unsigned int norandommap;
@@ -319,6 +320,7 @@ struct thread_options_pack {
 	uint32_t do_disk_util;
 	uint32_t override_sync;
 	uint32_t rand_repeatable;
+	uint32_t rand_seed;
 	uint32_t use_os_rand;
 	uint32_t log_avg_msec;
 	uint32_t norandommap;