Switch to using our internal Tausworthe based random generator for offsets
It's both faster and more exhaustive than what is available on
glibc on my test systems. So no downsides, and the upside of having
the same offset generator across all platforms.
This will change the random series, so could alter performance for
your workload since the pattern will be different in sequence. There's
an option to revert to the OS generator, you can add use_us_rand=1
on your job files to retain the old generator offsets.
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
diff --git a/HOWTO b/HOWTO
index d4e7092..69b8cc6 100644
--- a/HOWTO
+++ b/HOWTO
@@ -348,6 +348,12 @@
randrepeat=bool For random IO workloads, seed the generator in a predictable
way so that results are repeatable across repetitions.
+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
+ internal generator, which is often of better quality and
+ faster.
+
fallocate=bool By default, fio will use fallocate() to advise the system
of the size of the file we are going to write. This can be
turned off with fallocate=0. May not be available on all