X-Git-Url: https://git.kernel.dk/?p=fio.git;a=blobdiff_plain;f=HOWTO;h=de4b0a9932b43f207260a569a5e33349efebc63b;hp=8025cf513273a1cc4d9656170d19c0119f38881f;hb=bc5b77a8c46aabea554c4a2c8cca37f27f97969a;hpb=71bfa161f13b6fca98ba215ebebbcb5c99003d24 diff --git a/HOWTO b/HOWTO index 8025cf51..de4b0a99 100644 --- a/HOWTO +++ b/HOWTO @@ -49,10 +49,10 @@ bottom, it contains the following basic parameters: IO engine How do we issue io? We could be memory mapping the file, we could be using regular read/write, we - could be using splice, async io, or even + could be using splice, async io, syslet, or even SG (SCSI generic sg). - IO depth If the io engine is async, how large a queueing + IO depth If the io engine is async, how large a queuing depth do we want to maintain? IO type Should we be doing buffered io, or direct/raw io? @@ -82,9 +82,21 @@ more than one job file on the command line, fio will serialize the running of those files. Internally that is the same as using the 'stonewall' parameter described the the parameter section. +If the job file contains only one job, you may as well just give the +parameters on the command line. The command line parameters are identical +to the job parameters, with a few extra that control global parameters +(see README). For example, for the job file parameter iodepth=2, the +mirror command line option would be --iodepth 2 or --iodepth=2. You can +also use the command line for giving more than one job entry. For each +--name option that fio sees, it will start a new job with that name. +Command line entries following a --name entry will apply to that job, +until there are no more entries or a new --name entry is seen. This is +similar to the job file options, where each option applies to the current +job until a new [] job entry is seen. + fio does not need to run as root, except if the files or devices specified in the job section requires that. Some other options may also be restricted, -such as memory locking, io scheduler switching, and descreasing the nice value. +such as memory locking, io scheduler switching, and decreasing the nice value. 4.0 Job file format @@ -96,8 +108,8 @@ to use any ascii name you want, except 'global' which has special meaning. A global section sets defaults for the jobs described in that file. A job may override a global section parameter, and a job file may even have several global sections if so desired. A job is only affected by a global -section residing above it. If the first character in a line is a ';', the -entire line is discarded as a comment. +section residing above it. If the first character in a line is a ';' or a +'#', the entire line is discarded as a comment. So lets look at a really simple job file that define to threads, each randomly reading from a 128MiB file. @@ -115,7 +127,11 @@ size=128m As you can see, the job file sections themselves are empty as all the described parameters are shared. As no filename= option is given, fio -makes up a filename for each of the jobs as it sees fit. +makes up a filename for each of the jobs as it sees fit. On the command +line, this job would look as follows: + +$ fio --name=global --rw=randread --size=128m --name=job1 --name=job2 + Lets look at an example that have a number of processes writing randomly to files. @@ -136,7 +152,11 @@ Here we have no global section, as we only have one job defined anyway. We want to use async io here, with a depth of 4 for each file. We also increased the buffer size used to 32KiB and define numjobs to 4 to fork 4 identical jobs. The result is 4 processes each randomly writing -to their own 64MiB file. +to their own 64MiB file. Instead of using the above job file, you could +have given the parameters on the command line. For this case, you would +specify: + +$ fio --name=random-writers --ioengine=libaio --iodepth=4 --rw=randwrite --bs=32k --direct=0 --size=64m --numjobs=4 fio ships with a few example job files, you can also look there for inspiration. @@ -153,20 +173,29 @@ str String. This is a sequence of alpha characters. int Integer. A whole number value, may 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 specifiy 4096, + meaning kilo, mega, and giga. So if you want to specify 4096, you could either write out '4096' or just give 4k. The postfixes signify base 2 values, so 1024 is 1k and 1024k is 1m and so on. 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. name=str ASCII name of the job. This may be used to override the name printed by fio for this job. Otherwise the job - name is used. + name is used. On the command line this parameter has the + special purpose of also signaling the start of a new + job. + +description=str Text description of the job. Doesn't do anything except + dump this text description when this job is run. It's + not parsed. directory=str Prefix filenames with this directory. Used to places files in a different location than "./". @@ -174,7 +203,9 @@ directory=str Prefix filenames with this directory. Used to places files filename=str Fio normally makes up a filename based on the job name, thread number, and file number. If you want to share files between threads in a job or several jobs, specify - a filename for each of them to override the default. + a filename for each of them to override the default. If + the ioengine used is 'net', the filename is the host and + port to connect to in the format of =host:port. rw=str Type of io pattern. Accepted values are: @@ -189,6 +220,9 @@ 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 @@ -196,12 +230,26 @@ 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. +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. + 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 + direct IO, as that normally requires sector alignment. nrfiles=int Number of files to use for this job. Defaults to 1. @@ -222,19 +270,46 @@ ioengine=str Defines how the job issues io to the file. The following vmsplice(2) to transfer data from user space to the kernel. + syslet-rw Use the syslet system calls to make + regular read/write async. + sg SCSI generic sg v3 io. May either be - syncrhonous using the SG_IO ioctl, or if + synchronous using the SG_IO ioctl, or if the target is an sg character device 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. + + net Transfer over the network to given host:port. + 'filename' must be set appropriately to + filename=host:port regardless of send + or receive, if the latter only the port + argument is used. + 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. +iodepth_batch=int This defines how many pieces of IO to submit at once. + It defaults to the same as iodepth, but can be set lower + if one so desires. + +iodepth_low=int The low water mark indicating when to start filling + the queue again. Defaults to the same as iodepth, meaning + that fio will attempt to keep the queue full at all times. + If iodepth is set to eg 16 and iodepth_low is set to 4, then + after fio has filled the queue of 16 requests, it will let + the depth drain down to 4 before starting to fill it again. + 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 @@ -245,13 +320,13 @@ fsync=int If writing to a file, issue a sync of the dirty data 32 as a parameter, fio will sync the file for every 32 writes issued. If fio is using non-buffered io, we may not sync the file. The exception is the sg io engine, which - syncronizes the disk cache anyway. + synchronizes the disk cache anyway. overwrite=bool If writing to a file, setup the file first and do overwrites. end_fsync=bool If true, fsync file contents when the job exits. -rwmixcycle=int Value in miliseconds describing how often to switch between +rwmixcycle=int Value in milliseconds describing how often to switch between reads and writes for a mixed workload. The default is 500 msecs. @@ -262,6 +337,13 @@ rwmixwrite=int How large a percentage of the mix should be writes. If both up to 100%, the latter of the two will be used to override the first. +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 + 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. + 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 @@ -272,7 +354,20 @@ 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 and + thinktime_spin. + +thinktime_spin=int + Only valid if thinktime is set - pretend to spend CPU time + doing something with the data received, before falling back + to sleeping for the rest of the period specified by + thinktime. + +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. @@ -280,7 +375,7 @@ ratemin=int Tell fio to do whatever it can to maintain at least this bandwidth. ratecycle=int Average bandwidth for 'rate' and 'ratemin' over this number - of miliseconds. + of milliseconds. 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 @@ -291,7 +386,7 @@ 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. @@ -310,18 +405,48 @@ 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 desired action. bwavgtime=int Average the calculated bandwidth over the given time. Value - is specified in miliseconds. + is specified in milliseconds. create_serialize=bool If true, serialize the file creating for the jobs. This may be handy to avoid interleaving of data @@ -331,8 +456,9 @@ 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, - if it created the file itself. +unlink=bool Unlink the job files when done. Not the default, as repeated + runs of that job would then waste time recreating the fileset + again and again. loops=int Run the specified number of iterations of this job. Used to repeat the same workload a given number of times. Defaults @@ -347,7 +473,7 @@ 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. - This option can be used for repeated burnin tests of a + 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. @@ -369,15 +495,18 @@ zoneskip=siint Skip the specified number of bytes when zonesize data has been read. The two zone options can be used to only do io on zones of a file. -write_iolog=str Write the issued io patterns to the specified file. See iolog. +write_iolog=str Write the issued io patterns to the specified file. See + read_iolog. -iolog=str Open an iolog with the specified file name and replay the +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. 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 - jobs in their lifetime. + jobs in their lifetime. The included fio_generate_plots + script uses gnuplot to turn these text files into nice + graphs. write_lat_log Same as write_bw_log, except that this option stores io completion latencies instead. @@ -399,7 +528,7 @@ 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 miliseconds. + cycles of the given time. In milliseconds. 6.0 Interpreting the output @@ -408,7 +537,7 @@ 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] [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: @@ -430,9 +559,9 @@ E Thread exited, not reaped by main thread yet. _ Thread reaped. The other values are fairly self explanatory - number of threads -currently running and doing io, and the estimated completion percentage -and time for the running group. It's impossible to estimate runtime -of the following groups (if any). +currently running and doing io, rate of io since last check, and the estimated +completion percentage and time for the running group. It's impossible to +estimate runtime of the following groups (if any). When fio is done (or interrupted by ctrl-c), it will show the data for each thread, group of threads, and disks in that order. For each data @@ -440,10 +569,13 @@ 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% + 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% 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, @@ -468,6 +600,17 @@ 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. +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, + meaning that 2=1.6% means that 1.6% of the IO completed + within 2 msecs, 20=12.8% means that 12.8% of the IO + took more than 10 msecs, but less than (or equal to) 20 msecs. After each client has been listed, the group statistics are printed. They will look like this: @@ -505,7 +648,7 @@ util= The disk utilization. A value of 100% means we kept the disk ---------------- For scripted usage where you typically want to generate tables or graphs -of the results, fio can output the results in a comma seperated format. +of the results, fio can output the results in a comma separated format. The format is one long line of values, such as: client1,0,0,936,331,2894,0,0,0.000000,0.000000,1,170,22.115385,34.290410,16,714,84.252874%,366.500000,566.417819,3496,1237,2894,0,0,0.000000,0.000000,0,246,6.671625,21.436952,0,2534,55.465300%,1406.600000,2008.044216,0.000000%,0.431928%,1109 @@ -517,11 +660,11 @@ Split up, the format is as follows: KiB IO, bandwidth (KiB/sec), runtime (msec) Submission latency: min, max, mean, deviation Completion latency: min, max, mean, deviation - Bw: min, max, aggreate percentage of total, mean, deviation + Bw: min, max, aggregate percentage of total, mean, deviation WRITE status: KiB IO, bandwidth (KiB/sec), runtime (msec) Submission latency: min, max, mean, deviation Completion latency: min, max, mean, deviation - Bw: min, max, aggreate percentage of total, mean, deviation + Bw: min, max, aggregate percentage of total, mean, deviation CPU usage: user, system, context switches