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The following changes since commit fdba6ac393728b3f743013a6517a987fda79bd1a:

  Remove default setting of clocksource (2010-03-24 13:44:34 +0100)

are available in the git repository at:
  git://git.kernel.dk/fio.git master

Jens Axboe (8):
      Fix typo in bandwidth log command line option
      Keep the global command line bw/lat logs separate from per job logs
      First step at speeding up io_u rand refill
      Merge branch 'master' of ssh://brick.kernel.dk/data/git/fio
      Remember to prime the random generator
      "Expand" random number from 32-bit to 64-bit when necessary
      Add documentation for the random number generator
      Only use true random generator for initial seed

 Makefile         |    2 +
 Makefile.FreeBSD |    2 +
 Makefile.mac     |    2 +
 Makefile.solaris |    2 +
 fio.c            |    2 +
 init.c           |    5 +---
 io_u.c           |   10 ++++++++-
 lib/rand.c       |   59 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 lib/rand.h       |   23 +++++++++++++++++++++
 9 files changed, 102 insertions(+), 5 deletions(-)
 create mode 100644 lib/rand.c
 create mode 100644 lib/rand.h

---

Diff of recent changes:

diff --git a/Makefile b/Makefile
index 12042f4..837f421 100644
--- a/Makefile
+++ b/Makefile
@@ -9,6 +9,8 @@ OBJS = gettime.o fio.o ioengines.o init.o stat.o log.o time.o filesetup.o \
 	rbtree.o diskutil.o fifo.o blktrace.o smalloc.o filehash.o helpers.o \
 	cgroup.o profile.o debug.o
 
+OBJS += lib/rand.o
+
 OBJS += crc/crc7.o
 OBJS += crc/crc16.o
 OBJS += crc/crc32.o
diff --git a/Makefile.FreeBSD b/Makefile.FreeBSD
index deae03d..3c59a99 100644
--- a/Makefile.FreeBSD
+++ b/Makefile.FreeBSD
@@ -8,6 +8,8 @@ OBJS = gettime.o fio.o ioengines.o init.o stat.o log.o time.o filesetup.o \
 	eta.o verify.o memory.o io_u.o parse.o mutex.o options.o \
 	rbtree.o smalloc.o filehash.o helpers.o profile.o debug.o
 
+OBJS += lib/rand.o
+
 OBJS += crc/crc7.o
 OBJS += crc/crc16.o
 OBJS += crc/crc32.o
diff --git a/Makefile.mac b/Makefile.mac
index a726546..fe84297 100644
--- a/Makefile.mac
+++ b/Makefile.mac
@@ -8,6 +8,8 @@ OBJS = gettime.o fio.o ioengines.o init.o stat.o log.o time.o filesetup.o \
 	eta.o verify.o memory.o io_u.o parse.o mutex.o options.o \
 	rbtree.o smalloc.o filehash.o helpers.o profile.o debug.o
 
+OBJS += lib/rand.o
+
 OBJS += crc/crc7.o
 OBJS += crc/crc16.o
 OBJS += crc/crc32.o
diff --git a/Makefile.solaris b/Makefile.solaris
index 0ec6d73..49a4ef9 100644
--- a/Makefile.solaris
+++ b/Makefile.solaris
@@ -7,6 +7,8 @@ OBJS = gettime.o fio.o ioengines.o init.o stat.o log.o time.o filesetup.o \
 	rbtree.o fifo.o smalloc.o filehash.o lib/strsep.o helpers.o solaris.o \
 	profile.o debug.o
 
+OBJS += lib/rand.o
+
 OBJS += crc/crc7.o
 OBJS += crc/crc16.o
 OBJS += crc/crc32.o
diff --git a/fio.c b/fio.c
index dfda268..03dc6cc 100644
--- a/fio.c
+++ b/fio.c
@@ -41,6 +41,7 @@
 #include "diskutil.h"
 #include "cgroup.h"
 #include "profile.h"
+#include "lib/rand.h"
 
 unsigned long page_mask;
 unsigned long page_size;
@@ -1636,6 +1637,7 @@ int main(int argc, char *argv[])
 	long ps;
 
 	sinit();
+	init_rand(&__fio_rand_state);
 
 	/*
 	 * We need locale for number printing, if it isn't set then just
diff --git a/init.c b/init.c
index 4d0a906..69941b2 100644
--- a/init.c
+++ b/init.c
@@ -881,9 +881,6 @@ static int fill_def_thread(void)
 	fio_fill_default_options(&def_thread);
 
 	def_thread.o.timeout = def_timeout;
-	def_thread.o.write_bw_log = write_bw_log;
-	def_thread.o.write_lat_log = write_lat_log;
-
 	return 0;
 }
 
@@ -1076,7 +1073,7 @@ static int parse_cmd_line(int argc, char *argv[])
 		case 'l':
 			write_lat_log = 1;
 			break;
-		case 'w':
+		case 'b':
 			write_bw_log = 1;
 			break;
 		case 'o':
diff --git a/io_u.c b/io_u.c
index afc90de..23037f1 100644
--- a/io_u.c
+++ b/io_u.c
@@ -8,6 +8,7 @@
 #include "fio.h"
 #include "hash.h"
 #include "verify.h"
+#include "lib/rand.h"
 
 struct io_completion_data {
 	int nr;				/* input */
@@ -1216,9 +1217,16 @@ void io_u_fill_buffer(struct thread_data *td, struct io_u *io_u,
 	long *ptr = io_u->buf;
 
 	if (!td->o.zero_buffers) {
+		unsigned long r = __rand(&__fio_rand_state);
+
+		if (sizeof(int) != sizeof(*ptr))
+			r *= (unsigned long) __rand(&__fio_rand_state);
+
 		while ((void *) ptr - io_u->buf < max_bs) {
-			*ptr = rand() * GOLDEN_RATIO_PRIME;
+			*ptr = r;
 			ptr++;
+			r *= GOLDEN_RATIO_PRIME;
+			r >>= 3;
 		}
 	} else
 		memset(ptr, 0, max_bs);
diff --git a/lib/rand.c b/lib/rand.c
new file mode 100644
index 0000000..cecc4c2
--- /dev/null
+++ b/lib/rand.c
@@ -0,0 +1,59 @@
+/*
+  This is a maximally equidistributed combined Tausworthe generator
+  based on code from GNU Scientific Library 1.5 (30 Jun 2004)
+
+   x_n = (s1_n ^ s2_n ^ s3_n)
+
+   s1_{n+1} = (((s1_n & 4294967294) <<12) ^ (((s1_n <<13) ^ s1_n) >>19))
+   s2_{n+1} = (((s2_n & 4294967288) << 4) ^ (((s2_n << 2) ^ s2_n) >>25))
+   s3_{n+1} = (((s3_n & 4294967280) <<17) ^ (((s3_n << 3) ^ s3_n) >>11))
+
+   The period of this generator is about 2^88.
+
+   From: P. L'Ecuyer, "Maximally Equidistributed Combined Tausworthe
+   Generators", Mathematics of Computation, 65, 213 (1996), 203--213.
+
+   This is available on the net from L'Ecuyer's home page,
+
+   http://www.iro.umontreal.ca/~lecuyer/myftp/papers/tausme.ps
+   ftp://ftp.iro.umontreal.ca/pub/simulation/lecuyer/papers/tausme.ps
+
+   There is an erratum in the paper "Tables of Maximally
+   Equidistributed Combined LFSR Generators", Mathematics of
+   Computation, 68, 225 (1999), 261--269:
+   http://www.iro.umontreal.ca/~lecuyer/myftp/papers/tausme2.ps
+
+        ... the k_j most significant bits of z_j must be non-
+        zero, for each j. (Note: this restriction also applies to the
+        computer code given in [4], but was mistakenly not mentioned in
+        that paper.)
+
+   This affects the seeding procedure by imposing the requirement
+   s1 > 1, s2 > 7, s3 > 15.
+
+*/
+
+#include "rand.h"
+
+struct frand_state __fio_rand_state;
+
+static inline int __seed(unsigned int x, unsigned int m)
+{
+	return (x < m) ? x + m : x;
+}
+
+void init_rand(struct frand_state *state)
+{
+#define LCG(x)  ((x) * 69069)   /* super-duper LCG */
+
+	state->s1 = __seed(LCG((2^31) + (2^17) + (2^7)), 1);
+	state->s2 = __seed(LCG(state->s1), 7);
+	state->s3 = __seed(LCG(state->s2), 15);
+
+	__rand(state);
+	__rand(state);
+	__rand(state);
+	__rand(state);
+	__rand(state);
+	__rand(state);
+}
diff --git a/lib/rand.h b/lib/rand.h
new file mode 100644
index 0000000..363e7b6
--- /dev/null
+++ b/lib/rand.h
@@ -0,0 +1,23 @@
+#ifndef FIO_RAND_H
+#define FIO_RAND_H
+
+struct frand_state {
+	unsigned int s1, s2, s3;
+};
+
+extern struct frand_state __fio_rand_state;
+
+static inline unsigned int __rand(struct frand_state *state)
+{
+#define TAUSWORTHE(s,a,b,c,d) ((s&c)<<d) ^ (((s <<a) ^ s)>>b)
+
+	state->s1 = TAUSWORTHE(state->s1, 13, 19, 4294967294UL, 12);
+	state->s2 = TAUSWORTHE(state->s2, 2, 25, 4294967288UL, 4);
+	state->s3 = TAUSWORTHE(state->s3, 3, 11, 4294967280UL, 17);
+
+	return (state->s1 ^ state->s2 ^ state->s3);
+}
+
+extern void init_rand(struct frand_state *);
+
+#endif
--
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