X-Git-Url: https://git.kernel.dk/?p=fio.git;a=blobdiff_plain;f=HOWTO;h=6391b82a9c79b31fe3e3b0f2fac2dd0b6caf57ae;hp=40fe65fe9bc6d65cfc14cbe2e5565189fee2ae9d;hb=92d42d69755e9547f73d782466c453c5c9b67517;hpb=5881fda43ce41756029a830cc83dbf4480cb6ea2

diff --git a/HOWTO b/HOWTO
index 40fe65fe..6391b82a 100644
--- a/HOWTO
+++ b/HOWTO
@@ -716,6 +716,25 @@ rwmixwrite=int	How large a percentage of the mix should be writes. If both
 		if fio is asked to limit reads or writes to a certain rate.
 		If that is the case, then the distribution may be skewed.
 
+random_distribution=str:float	By default, fio will use a completely uniform
+		random distribution when asked to perform random IO. Sometimes
+		it is useful to skew the distribution in specific ways,
+		ensuring that some parts of the data is more hot than others.
+		fio includes the following distribution models:
+
+		random		Uniform random distribution
+		zipf		Zipf distribution
+		pareto		Pareto distribution
+
+		When using a zipf or pareto distribution, an input value
+		is also needed to define the access pattern. For zipf, this
+		is the zipf theta. For pareto, it's the pareto power. Fio
+		includes a test program, genzipf, that can be used visualize
+		what the given input values will yield in terms of hit rates.
+		If you wanted to use zipf with a theta of 1.2, you would use
+		random_distribution=zipf:1.2 as the option. If a non-uniform
+		model is used, fio will disable use of the random map.
+
 norandommap	Normally fio will cover every block of the file when doing
 		random IO. If this option is given, fio will just get a
 		new random offset without looking at past io history. This