From e8b1961dd3470be277d31d3ddd6eeef885c1cfe2 Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Wed, 5 Dec 2012 10:28:08 +0100 Subject: [PATCH] lfsr: add HOWTO and man page documentation Signed-off-by: Jens Axboe --- HOWTO | 17 +++++++++++++++++ fio.1 | 20 ++++++++++++++++++++ 2 files changed, 37 insertions(+) diff --git a/HOWTO b/HOWTO index 32e5d668..6d541afb 100644 --- a/HOWTO +++ b/HOWTO @@ -753,6 +753,23 @@ softrandommap=bool See norandommap. If fio runs with the random block map will not be as complete as with random maps, this option is disabled by default. +random_generator=str Fio supports the following engines for generating + IO offsets for random IO: + + tausworthe Strong 2^88 cycle random number generator + lfsr Linear feedback shift register generator + + Tausworthe is a strong random number generator, but it + requires tracking on the side if we want to ensure that + blocks are only read or written once. LFSR guarantees + that we never generate the same offset twice, and it's + also less computationally expensive. It's not a true + random generator, however, though for IO purposes it's + typically good enough. LFSR only works with single + block sizes, not with workloads that use multiple block + sizes. If used with such a workload, fio may read or write + some blocks multiple times. + nice=int Run the job with the given nice value. See man nice(2). prio=int Set the io priority value of this job. Linux limits us to diff --git a/fio.1 b/fio.1 index 2db9793f..7c622938 100644 --- a/fio.1 +++ b/fio.1 @@ -617,6 +617,26 @@ fails to allocate the map, if this option is set it will continue without a random block map. As coverage will not be as complete as with random maps, this option is disabled by default. .TP +.BI random_generator \fR=\fPstr +Fio supports the following engines for generating IO offsets for random IO: +.RS +.TP +.B tausworthe +Strong 2^88 cycle random number generator +.TP +.B lfsr +Linear feedback shift register generator +.TP +.RE +.P +Tausworthe is a strong random number generator, but it requires tracking on the +side if we want to ensure that blocks are only read or written once. LFSR +guarantees that we never generate the same offset twice, and it's also less +computationally expensive. It's not a true random generator, however, though +for IO purposes it's typically good enough. LFSR only works with single block +sizes, not with workloads that use multiple block sizes. If used with such a +workload, fio may read or write some blocks multiple times. +.TP .BI nice \fR=\fPint Run job with given nice value. See \fInice\fR\|(2). .TP -- 2.25.1