X-Git-Url: https://git.kernel.dk/?p=fio.git;a=blobdiff_plain;f=HOWTO;h=95d059e766e6399f29d8097331a076db4df29161;hp=2616156d1234017a1d08da368c3bb461c29fcf0a;hb=71619dc28506f7b7b40905b942e992b02f0d5b96;hpb=6c21976321b14966466cdcd7a1636c303ecf43c0 diff --git a/HOWTO b/HOWTO index 2616156d..95d059e7 100644 --- a/HOWTO +++ b/HOWTO @@ -179,7 +179,10 @@ siint SI integer. A whole number value, which may contain a postfix bool Boolean. Usually parsed as an integer, however only defined for true and false (1 and 0). irange Integer range with postfix. Allows value range to be given, such - as 1024-4096. Also see siint. + as 1024-4096. A colon may also be used as the seperator, eg + 1k:4k. If the option allows two sets of ranges, they can be + specified with a ',' or '/' delimiter: 1k-4k/8k-32k. Also see + siint. With the above in mind, here follows the complete list of fio job parameters. @@ -211,6 +214,9 @@ rw=str Type of io pattern. Accepted values are: For certain types of io the result may still be skewed a bit, since the speed may be different. +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 @@ -218,22 +224,22 @@ size=siint The total size of file io for this job. This may describe size if larger than the current file size. If this parameter is not given and the file exists, the file size will be used. -bs=siint The block size used for the io units. Defaults to 4k. - -read_bs=siint -write_bs=siint If the workload is a mixed read-write workload, you can use - these options to set separate block sizes. +bs=siint The block size used for the io units. Defaults to 4k. Values + can be given for both read and writes. If a single siint is + given, it will apply to both. If a second siint is specified + after a comma, it will apply to writes only. In other words, + the format is either bs=read_and_write or bs=read,write. + bs=4k,8k will thus use 4k blocks for reads, and 8k blocks + for writes. If you only wish to set the write size, you + can do so by passing an empty read size - bs=,8k will set + 8k for writes and leave the read default value. bsrange=irange Instead of giving a single block size, specify a range and fio will mix the issued io block sizes. The issued io unit will always be a multiple of the minimum value - given (also see bs_unaligned). - -read_bsrange=irange -write_bsrange=irange - If the workload is a mixed read-write workload, you can use - one of these options to set separate block size ranges for - reads and writes. + given (also see bs_unaligned). Applies to both reads and + writes, however a second range can be given after a comma. + See bs=. 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 @@ -264,13 +270,20 @@ ioengine=str Defines how the job issues io to the file. The following we use read(2) and write(2) for asynchronous io. + null Doesn't transfer any data, just pretends + to. This is mainly used to exercise fio + itself and for debugging/testing purposes. + iodepth=int This defines how many io units to keep in flight against the file. The default is 1 for each file defined in this job, can be overridden with a larger value for higher concurrency. direct=bool If value is true, use non-buffered io. This is usually - O_DIRECT. Defaults to true. + O_DIRECT. + +buffered=bool If value is true, use buffered io. This is the opposite + of the 'direct' option. Defaults to true. offset=siint Start io at the given offset in the file. The data before the given offset will not be touched. This effectively @@ -315,7 +328,13 @@ prioclass=int Set the io priority class. See man ionice(1). thinktime=int Stall the job x microseconds after an io has completed before issuing the next. May be used to simulate processing being - done by an application. + done by an application. See thinktime_blocks. + +thinktime_blocks + 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. rate=int Cap the bandwidth used by this job to this number of KiB/sec. @@ -334,7 +353,7 @@ startdelay=int Start this job the specified number of seconds after fio jobs, and you want to delay starting some jobs to a certain time. -timeout=int Tell fio to terminate processing after the specified number +runtime=int Tell fio to terminate processing after the specified number of seconds. It can be quite hard to determine for how long a specified job will run, so this parameter is handy to cap the total runtime to a given time. @@ -353,11 +372,41 @@ mem=str Fio can use various types of memory as the io unit buffer. shm Use shared memory as the buffers. Allocated through shmget(2). - mmap Use anonymous memory maps as the buffers. - Allocated through mmap(2). + shmhuge Same as shm, but use huge pages as backing. + + mmap Use mmap to allocate buffers. May either be + anonymous memory, or can be file backed if + a filename is given after the option. The + format is mem=mmap:/path/to/file. + + mmaphuge Use a memory mapped huge file as the buffer + backing. Append filename after mmaphuge, ala + mem=mmaphuge:/hugetlbfs/file The area allocated is a function of the maximum allowed - bs size for the job, multiplied by the io depth given. + bs size for the job, multiplied by the io depth given. Note + that for shmhuge and mmaphuge to work, the system must have + free huge pages allocated. This can normally be checked + and set by reading/writing /proc/sys/vm/nr_hugepages on a + Linux system. Fio assumes a huge page is 4MiB in size. So + to calculate the number of huge pages you need for a given + job file, add up the io depth of all jobs (normally one unless + iodepth= is used) and multiply by the maximum bs set. Then + divide that number by the huge page size. You can see the + size of the huge pages in /proc/meminfo. If no huge pages + are allocated by having a non-zero number in nr_hugepages, + using mmaphuge or shmhuge will fail. Also see hugepage-size. + + mmaphuge also needs to have hugetlbfs mounted and the file + location should point there. So if it's mounted in /huge, + you would use mem=mmaphuge:/huge/somefile. + +hugepage-size=siint + Defines the size of a huge page. Must at least be equal + to the system setting, see /proc/meminfo. Defaults to 4MiB. + Should probably always be a multiple of megabytes, so using + hugepage-size=Xm is the preferred way to set this to avoid + setting a non-pow-2 bad value. exitall When one job finishes, terminate the rest. The default is to wait for each job to finish, sometimes that is not the @@ -374,7 +423,7 @@ create_serialize=bool If true, serialize the file creating for the jobs. create_fsync=bool fsync the data file after creation. This is the default. -unlink Unlink the job files when done. fio defaults to doing this, +unlink=bool Unlink the job files when done. fio defaults to doing this, if it created the file itself. loops=int Run the specified number of iterations of this job. Used @@ -454,7 +503,7 @@ cpuchunks=int If the job is a CPU cycle eater, split the load into fio spits out a lot of output. While running, fio will display the status of the jobs created. An example of that would be: -Threads running: 1: [_r] [24.79% done] [ 13509/ 8334 kb/s] [eta 00h:01m:31s] +Threads: 1: [_r] [24.8% done] [ 13509/ 8334 kb/s] [eta 00h:01m:31s] The characters inside the square brackets denote the current status of each thread. The possible values (in typical life cycle order) are: @@ -486,10 +535,11 @@ direction, the output looks like: Client1 (g=0): err= 0: write: io= 32MiB, bw= 666KiB/s, runt= 50320msec - slat (msec): min= 0, max= 136, avg= 0.03, dev= 1.92 - clat (msec): min= 0, max= 631, avg=48.50, dev=86.82 - bw (KiB/s) : min= 0, max= 1196, per=51.00%, avg=664.02, dev=681.68 + slat (msec): min= 0, max= 136, avg= 0.03, stdev= 1.92 + clat (msec): min= 0, max= 631, avg=48.50, stdev=86.82 + 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% The client number is printed, along with the group id and error of that thread. Below is the io statistics, here for writes. In the order listed, @@ -514,6 +564,11 @@ runt= The runtime of that thread same disk, since they are then competing for disk access. cpu= CPU usage. User and system time, along with the number of context switches this thread went through. +IO depths= The distribution of io depths over the job life time. The + numbers are divided into powers of 2, so for example 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. After each client has been listed, the group statistics are printed. They will look like this: