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author | Jens Axboe <axboe@kernel.dk> | 2012-11-15 15:38:32 -0700 |
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committer | Jens Axboe <axboe@kernel.dk> | 2012-11-15 15:38:32 -0700 |

commit | 92d42d69755e9547f73d782466c453c5c9b67517 (patch) | |

tree | 5731d33f333d36a339619b2b08b72161432bc102 | |

parent | 5881fda43ce41756029a830cc83dbf4480cb6ea2 (diff) | |

download | fio-92d42d69755e9547f73d782466c453c5c9b67517.tar.gz fio-92d42d69755e9547f73d782466c453c5c9b67517.tar.bz2 |

Document random distribution

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

-rw-r--r-- | HOWTO | 19 | ||||

-rw-r--r-- | fio.1 | 26 |

2 files changed, 45 insertions, 0 deletions

@@ -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 @@ -580,6 +580,32 @@ overrides the first. This may interfere with a given rate setting, if fio is asked to limit reads or writes to a certain rate. If that is the case, then the distribution may be skewed. Default: 50. .TP +.BI random_distribution \fR=\fPstr: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: +.RS +.TP +.B random +Uniform random distribution +.TP +.B zipf +Zipf distribution +.TP +.B pareto +Pareto distribution +.TP +.RE +.P +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. +.TP .B norandommap Normally \fBfio\fR will cover every block of the file when doing random I/O. If this parameter is given, a new offset will be chosen without looking at past |