X-Git-Url: https://git.kernel.dk/?p=fio.git;a=blobdiff_plain;f=HOWTO;h=99cbaea37eb760dca27875eab9bcb8bd9def2292;hp=051a4554a95ff8a1229d3154a1c6bd31f701c9c6;hb=7616cafe9c2c76451e518eafe5cc37db460c8b1e;hpb=211097b2aa664b8c157692a1e2fe656ed4a3488c diff --git a/HOWTO b/HOWTO index 051a4554..99cbaea3 100644 --- a/HOWTO +++ b/HOWTO @@ -170,7 +170,7 @@ Some parameters take an option of a given type, such as an integer or a string. The following types are used: str String. This is a sequence of alpha characters. -int Integer. A whole number value, may be negative. +int Integer. A whole number value, can be negative. siint SI integer. A whole number value, which may contain a postfix describing the base of the number. Accepted postfixes are k/m/g, meaning kilo, mega, and giga. So if you want to specify 4096, @@ -211,7 +211,9 @@ filename=str Fio normally makes up a filename based on the job name, ioengine is file based, you can specify a number of files by seperating the names with a ':' colon. So if you wanted a job to open /dev/sda and /dev/sdb as the two working files, - you would use filename=/dev/sda:/dev/sdb + you would use filename=/dev/sda:/dev/sdb. '-' is a reserved + name, meaning stdin or stdout. Which of the two depends + on the read/write direction set. opendir=str Tell fio to recursively add any file it can find in this directory and down the file system tree. @@ -240,12 +242,19 @@ rw=str Type of io pattern. Accepted values are: randrepeat=bool For random IO workloads, seed the generator in a predictable way so that results are repeatable across repetitions. -size=siint The total size of file io for this job. This may describe - the size of the single file the job uses, or it may be - divided between the number of files in the job. If the - file already exists, the file size will be adjusted to this - size if larger than the current file size. If this parameter - is not given and the file exists, the file size will be used. +fadvise_hint=bool By default, fio will use fadvise() to advise the kernel + on what IO patterns it is likely to issue. Sometimes you + want to test specific IO patterns without telling the + kernel about it, in which case you can disable this option. + If set, fio will use POSIX_FADV_SEQUENTIAL for sequential + IO and POSIX_FADV_RANDOM for random IO. + +size=siint The total size of file io for this job. Fio will run until + this many bytes has been transferred, unless runtime is + limited by other options (such as 'runtime', for instance). + Unless specific nr_files and filesize options are given, + fio will divide this size between the available files + specified by the job. filesize=siint Individual file sizes. May be a range, in which case fio will select sizes for files at random within the given range @@ -276,6 +285,9 @@ bs_unaligned If this option is given, any byte size value within bsrange may be used as a block range. This typically wont work with direct IO, as that normally requires sector alignment. +zero_buffers If this option is given, fio will init the IO buffers to + all zeroes. The default is to fill them with random data. + nrfiles=int Number of files to use for this job. Defaults to 1. openfiles=int Number of files to keep open at the same time. Defaults to @@ -407,7 +419,9 @@ norandommap Normally fio will cover every block of the file when doing new random offset without looking at past io history. This means that some blocks may not be read or written, and that some blocks may be read/written more than once. This option - is mutually exclusive with verify= for that reason. + is mutually exclusive with verify= for that reason, since + fio doesn't track potential block rewrites which may alter + the calculated checksum for that block. nice=int Run the job with the given nice value. See man nice(2). @@ -453,7 +467,8 @@ ratecycle=int Average bandwidth for 'rate' and 'ratemin' over this number cpumask=int Set the CPU affinity of this job. The parameter given is a bitmask of allowed CPU's the job may run on. See man - sched_setaffinity(2). + sched_setaffinity(2). This may not work on all supported + operating systems or kernel versions. startdelay=int Start this job the specified number of seconds after fio has started. Only useful if the job file contains several @@ -465,6 +480,11 @@ runtime=int Tell fio to terminate processing after the specified number a specified job will run, so this parameter is handy to cap the total runtime to a given time. +time_based If set, fio will run for the duration of the runtime + specified even if the file(s) are completey read or + written. It will simply loop over the same workload + as many times as the runtime allows. + invalidate=bool Invalidate the buffer/page cache parts for this file prior to starting io. Defaults to true. @@ -548,10 +568,22 @@ verify=str If writing to a file, fio can verify the file contents crc32 Use a crc32 sum of the data area and store it in the header of each block. + null Only pretend to verify. Useful for testing + internals with ioengine=null, not for much + else. + This option can be used for repeated burn-in tests of a system to make sure that the written data is also correctly read back. +verifysort=bool If set, fio will sort written verify blocks when it deems + it faster to read them back in a sorted manner. This is + often the case when overwriting an existing file, since + the blocks are already laid out in the file system. You + can ignore this option unless doing huge amounts of really + fast IO where the red-black tree sorting CPU time becomes + significant. + stonewall Wait for preceeding jobs in the job file to exit, before starting this one. Can be used to insert serialization points in the job file. A stone wall also implies starting @@ -589,7 +621,12 @@ write_iolog=str Write the issued io patterns to the specified file. See read_iolog=str Open an iolog with the specified file name and replay the io patterns it contains. This can be used to store a - workload and replay it sometime later. + workload and replay it sometime later. The iolog given + may also be a blktrace binary file, which allows fio + to replay a workload captured by blktrace. See blktrace + for how to capture such logging data. For blktrace replay, + the file needs to be turned into a blkparse binary data + file first (blktrace -d file_for_fio.bin). write_bw_log If given, write a bandwidth log of the jobs in this job file. Can be used to store data of the bandwidth of the @@ -619,6 +656,9 @@ cpuload=int If the job is a CPU cycle eater, attempt to use the specified cpuchunks=int If the job is a CPU cycle eater, split the load into cycles of the given time. In milliseconds. +disk_util=bool Generate disk utilization statistics, if the platform + supports it. Defaults to on. + 6.0 Interpreting the output --------------------------- @@ -663,6 +703,7 @@ Client1 (g=0): err= 0: bw (KiB/s) : min= 0, max= 1196, per=51.00%, avg=664.02, stdev=681.68 cpu : usr=1.49%, sys=0.25%, ctx=7969 IO depths : 1=0.1%, 2=0.3%, 4=0.5%, 8=99.0%, 16=0.0%, 32=0.0%, >32=0.0% + issued r/w: total=0/32768, short=0/0 lat (msec): 2=1.6%, 4=0.0%, 10=3.2%, 20=12.8%, 50=38.4%, 100=24.8%, lat (msec): 250=15.2%, 500=0.0%, 750=0.0%, 1000=0.0%, >=2048=0.0% @@ -694,6 +735,8 @@ IO depths= The distribution of io depths over the job life time. The 16= entries includes depths up to that value but higher than the previous entry. In other words, it covers the range from 16 to 31. +IO issued= The number of read/write requests issued, and how many + of them were short. IO latencies= The distribution of IO completion latencies. This is the time from when IO leaves fio and when it gets completed. The numbers follow the same pattern as the IO depths,