X-Git-Url: https://git.kernel.dk/?p=fio.git;a=blobdiff_plain;f=HOWTO;h=794728f3b2cf3b3d9edc3a7493ce157c8a5901ea;hp=76effeef9e1b2bc2c9d0254301a9c9042dd50692;hb=b9ea0c31d25a6f3b88925398158463863d44c3c2;hpb=7351f402b131fc4ad4e25bd2609a255a1ab4e97c diff --git a/HOWTO b/HOWTO index 76effeef..794728f3 100644 --- a/HOWTO +++ b/HOWTO @@ -568,6 +568,8 @@ ioengine=str Defines how the job issues io to the file. The following vsync Basic readv(2) or writev(2) IO. + psyncv Basic preadv(2) or pwritev(2) IO. + libaio Linux native asynchronous io. Note that Linux may only support queued behaviour with non-buffered IO (set direct=1 or buffered=0). @@ -766,6 +768,17 @@ random_distribution=str:float By default, fio will use a completely uniform random_distribution=zipf:1.2 as the option. If a non-uniform model is used, fio will disable use of the random map. +percentage_random=int For a random workload, set how big a percentage should + be random. This defaults to 100%, in which case the workload + is fully random. It can be set from anywhere from 0 to 100. + Setting it to 0 would make the workload fully sequential. Any + setting in between will result in a random mix of sequential + and random IO, at the given percentages. + +percentage_sequential=int See percentage_random. It is guaranteed that + they add up to 100. The later setting has priority, each + will adjust the other. + 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 @@ -817,11 +830,15 @@ thinktime_spin=int to sleeping for the rest of the period specified by thinktime. -thinktime_blocks +thinktime_blocks=int Only valid if thinktime is set - control how many blocks to issue, before waiting 'thinktime' usecs. If not set, defaults to 1 which will make fio wait 'thinktime' usecs - after every block. + after every block. This effectively makes any queue depth + setting redundant, since no more than 1 IO will be queued + before we have to complete it and do our thinktime. In + other words, this setting effectively caps the queue depth + if the latter is larger. rate=int Cap the bandwidth used by this job. The number is in bytes/sec, the normal suffix rules apply. You can use rate=500k to limit @@ -1219,7 +1236,7 @@ write_lat_log=str Same as write_bw_log, except that this option stores io write_lat_log=foo - The actual log names will be foo_slat.log, foo_slat.log, + The actual log names will be foo_slat.log, foo_clat.log, and foo_lat.log. This helps fio_generate_plot fine the logs automatically. @@ -1241,6 +1258,7 @@ log_avg_msec=int By default, fio will log an entry in the iops, latency, lockmem=int Pin down the specified amount of memory with mlock(2). Can potentially be used instead of removing memory or booting with less memory to simulate a smaller amount of memory. + The amount specified is per worker. exec_prerun=str Before running this job, issue the command specified through system(3). @@ -1251,12 +1269,6 @@ exec_postrun=str After the job completes, issue the command specified ioscheduler=str Attempt to switch the device hosting the file to the specified io scheduler before running. -cpuload=int If the job is a CPU cycle eater, attempt to use the specified - percentage of CPU cycles. - -cpuchunks=int If the job is a CPU cycle eater, split the load into - cycles of the given time. In microseconds. - disk_util=bool Generate disk utilization statistics, if the platform supports it. Defaults to on. @@ -1416,6 +1428,11 @@ that defines them is selected. enabled when polling for a minimum of 0 events (eg when iodepth_batch_complete=0). +[cpu] cpuload=int Attempt to use the specified percentage of CPU cycles. + +[cpu] cpuchunks=int Split the load into cycles of the given time. In + microseconds. + [netsplice] hostname=str [net] hostname=str The host name or IP address to use for TCP or UDP based IO. If the job is a TCP listener or UDP reader, the hostname is not @@ -1600,6 +1617,9 @@ util= The disk utilization. A value of 100% means we kept the disk It is also possible to get fio to dump the current output while it is running, without terminating the job. To do that, send fio the USR1 signal. +You can also get regularly timed dumps by using the --status-interval +parameter, or by creating a file in /tmp named fio-dump-status. If fio +sees this file, it will unlink it and dump the current output status. 7.0 Terse output @@ -1721,7 +1741,7 @@ trim trim the given file from the given 'offset' for 'length' bytes 9.0 CPU idleness profiling - +-------------------------- In some cases, we want to understand CPU overhead in a test. For example, we test patches for the specific goodness of whether they reduce CPU usage. fio implements a balloon approach to create a thread per CPU that runs at