.TH fio 1 "September 2007" "User Manual" .SH NAME fio \- flexible I/O tester .SH SYNOPSIS .B fio [\fIoptions\fR] [\fIjobfile\fR]... .SH DESCRIPTION .B fio is a tool that will spawn a number of threads or processes doing a particular type of I/O action as specified by the user. The typical use of fio is to write a job file matching the I/O load one wants to simulate. .SH OPTIONS .TP .BI \-\-output \fR=\fPfilename Write output to \fIfilename\fR. .TP .BI \-\-timeout \fR=\fPtimeout Limit run time to \fItimeout\fR seconds. .TP .B \-\-latency\-log Generate per-job latency logs. .TP .B \-\-bandwidth\-log Generate per-job bandwidth logs. .TP .B \-\-minimal Print statistics in a terse, semicolon-delimited format. .TP .BI \-\-showcmd \fR=\fPjobfile Convert \fIjobfile\fR to a set of command-line options. .TP .B \-\-readonly Enable read-only safety checks. .TP .BI \-\-eta \fR=\fPwhen Specifies when real-time ETA estimate should be printed. \fIwhen\fR may be one of `always', `never' or `auto'. .TP .BI \-\-section \fR=\fPsec Only run section \fIsec\fR from job file. .TP .BI \-\-cmdhelp \fR=\fPcommand Print help information for \fIcommand\fR. May be `all' for all commands. .TP .BI \-\-debug \fR=\fPtype Enable verbose tracing of various fio actions. May be `all' for all types or individual types seperated by a comma (eg \-\-debug=io,file). `help' will list all available tracing options. .TP .B \-\-help Display usage information and exit. .TP .B \-\-version Display version information and exit. .SH "JOB FILE FORMAT" Job files are in `ini' format. They consist of one or more job definitions, which begin with a job name in square brackets and extend to the next job name. The job name can be any ASCII string except `global', which has a special meaning. Following the job name is a sequence of zero or more parameters, one per line, that define the behavior of the job. Any line starting with a `;' or `#' character is considered a comment and ignored. .P If \fIjobfile\fR is specified as `-', the job file will be read from standard input. .SS "Global Section" The global section contains default parameters for jobs specified in the job file. A job is only affected by global sections residing above it, and there may be any number of global sections. Specific job definitions may override any parameter set in global sections. .SH "JOB PARAMETERS" .SS Types Some parameters may take arguments of a specific type. The types used are: .TP .I str String: a sequence of alphanumeric characters. .TP .I int SI integer: a whole number, possibly containing a suffix denoting the base unit of the value. Accepted suffixes are `k', 'M', 'G', 'T', and 'P', denoting kilo (1024), mega (1024^2), giga (1024^3), tera (1024^4), and peta (1024^5) respectively. The suffix is not case sensitive. If prefixed with '0x', the value is assumed to be base 16 (hexadecimal). .TP .I bool Boolean: a true or false value. `0' denotes false, `1' denotes true. .TP .I irange Integer range: a range of integers specified in the format \fIlower\fR:\fIupper\fR or \fIlower\fR\-\fIupper\fR. \fIlower\fR and \fIupper\fR may contain a suffix as described above. If an option allows two sets of ranges, they are separated with a `,' or `/' character. For example: `8\-8k/8M\-4G'. .SS "Parameter List" .TP .BI name \fR=\fPstr May be used to override the job name. On the command line, this parameter has the special purpose of signalling the start of a new job. .TP .BI description \fR=\fPstr Human-readable description of the job. It is printed when the job is run, but otherwise has no special purpose. .TP .BI directory \fR=\fPstr Prefix filenames with this directory. Used to place files in a location other than `./'. .TP .BI filename \fR=\fPstr .B fio normally makes up a file name 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 \fIfilename\fR for each of them to override the default. If the I/O engine used is `net', \fIfilename\fR is the host and port to connect to in the format \fIhost\fR/\fIport\fR. If the I/O engine is file-based, you can specify a number of files by separating the names with a `:' character. `\-' is a reserved name, meaning stdin or stdout, depending on the read/write direction set. .TP .BI lockfile \fR=\fPstr Fio defaults to not locking any files before it does IO to them. If a file or file descriptor is shared, fio can serialize IO to that file to make the end result consistent. This is usual for emulating real workloads that share files. The lock modes are: .RS .RS .TP .B none No locking. This is the default. .TP .B exclusive Only one thread or process may do IO at the time, excluding all others. .TP .B readwrite Read-write locking on the file. Many readers may access the file at the same time, but writes get exclusive access. .RE .P The option may be post-fixed with a lock batch number. If set, then each thread/process may do that amount of IOs to the file before giving up the lock. Since lock acquisition is expensive, batching the lock/unlocks will speed up IO. .RE .P .BI opendir \fR=\fPstr Recursively open any files below directory \fIstr\fR. .TP .BI readwrite \fR=\fPstr "\fR,\fP rw" \fR=\fPstr Type of I/O pattern. Accepted values are: .RS .RS .TP .B read Sequential reads. .TP .B write Sequential writes. .TP .B randread Random reads. .TP .B randwrite Random writes. .TP .B rw Mixed sequential reads and writes. .TP .B randrw Mixed random reads and writes. .RE .P For mixed I/O, the default split is 50/50. For random I/O, the number of I/Os to perform before getting a new offset can be specified by appending `:\fIint\fR' to the pattern type. The default is 1. .RE .TP .BI kb_base \fR=\fPint The base unit for a kilobyte. The defacto base is 2^10, 1024. Storage manufacturers like to use 10^3 or 1000 as a base ten unit instead, for obvious reasons. Allow values are 1024 or 1000, with 1024 being the default. .TP .BI randrepeat \fR=\fPbool Seed the random number generator in a predictable way so results are repeatable across runs. Default: true. .TP .BI fallocate \fR=\fPbool By default, fio will use fallocate() to advise the system of the size of the file we are going to write. This can be turned off with fallocate=0. May not be available on all supported platforms. .TP .BI fadvise_hint \fR=\fPbool Disable use of \fIposix_fadvise\fR\|(2) to advise the kernel what I/O patterns are likely to be issued. Default: true. .TP .BI size \fR=\fPint Total size of I/O for this job. \fBfio\fR will run until this many bytes have been transfered, unless limited by other options (\fBruntime\fR, for instance). Unless \fBnr_files\fR and \fBfilesize\fR options are given, this amount will be divided between the available files for the job. .TP .BI fill_device \fR=\fPbool Sets size to something really large and waits for ENOSPC (no space left on device) as the terminating condition. Only makes sense with sequential write. For a read workload, the mount point will be filled first then IO started on the result. .TP .BI filesize \fR=\fPirange Individual file sizes. May be a range, in which case \fBfio\fR will select sizes for files at random within the given range, limited to \fBsize\fR in total (if that is given). If \fBfilesize\fR is not specified, each created file is the same size. .TP .BI blocksize \fR=\fPint[,int] "\fR,\fB bs" \fR=\fPint[,int] Block size for I/O units. Default: 4k. Values for reads and writes can be specified seperately in the format \fIread\fR,\fIwrite\fR, either of which may be empty to leave that value at its default. .TP .BI blocksize_range \fR=\fPirange[,irange] "\fR,\fB bsrange" \fR=\fPirange[,irange] Specify a range of I/O block sizes. The issued I/O unit will always be a multiple of the minimum size, unless \fBblocksize_unaligned\fR is set. Applies to both reads and writes if only one range is given, but can be specified seperately with a comma seperating the values. Example: bsrange=1k-4k,2k-8k. Also (see \fBblocksize\fR). .TP .BI bssplit \fR=\fPstr This option allows even finer grained control of the block sizes issued, not just even splits between them. With this option, you can weight various block sizes for exact control of the issued IO for a job that has mixed block sizes. The format of the option is bssplit=blocksize/percentage, optionally adding as many definitions as needed seperated by a colon. Example: bssplit=4k/10:64k/50:32k/40 would issue 50% 64k blocks, 10% 4k blocks and 40% 32k blocks. \fBbssplit\fR also supports giving separate splits to reads and writes. The format is identical to what the \fBbs\fR option accepts, the read and write parts are separated with a comma. .TP .B blocksize_unaligned\fR,\fP bs_unaligned If set, any size in \fBblocksize_range\fR may be used. This typically won't work with direct I/O, as that normally requires sector alignment. .TP .BI blockalign \fR=\fPint[,int] "\fR,\fB ba" \fR=\fPint[,int] At what boundary to align random IO offsets. Defaults to the same as 'blocksize' the minimum blocksize given. Minimum alignment is typically 512b for using direct IO, though it usually depends on the hardware block size. This option is mutually exclusive with using a random map for files, so it will turn off that option. .TP .B zero_buffers Initialise buffers with all zeros. Default: fill buffers with random data. .TP .B refill_buffers If this option is given, fio will refill the IO buffers on every submit. The default is to only fill it at init time and reuse that data. Only makes sense if zero_buffers isn't specified, naturally. If data verification is enabled, refill_buffers is also automatically enabled. .TP .BI nrfiles \fR=\fPint Number of files to use for this job. Default: 1. .TP .BI openfiles \fR=\fPint Number of files to keep open at the same time. Default: \fBnrfiles\fR. .TP .BI file_service_type \fR=\fPstr Defines how files to service are selected. The following types are defined: .RS .RS .TP .B random Choose a file at random .TP .B roundrobin Round robin over open files (default). .B sequential Do each file in the set sequentially. .RE .P The number of I/Os to issue before switching a new file can be specified by appending `:\fIint\fR' to the service type. .RE .TP .BI ioengine \fR=\fPstr Defines how the job issues I/O. The following types are defined: .RS .RS .TP .B sync Basic \fIread\fR\|(2) or \fIwrite\fR\|(2) I/O. \fIfseek\fR\|(2) is used to position the I/O location. .TP .B psync Basic \fIpread\fR\|(2) or \fIpwrite\fR\|(2) I/O. .TP .B vsync Basic \fIreadv\fR\|(2) or \fIwritev\fR\|(2) I/O. Will emulate queuing by coalescing adjacents IOs into a single submission. .TP .B libaio Linux native asynchronous I/O. .TP .B posixaio glibc POSIX asynchronous I/O using \fIaio_read\fR\|(3) and \fIaio_write\fR\|(3). .TP .B mmap File is memory mapped with \fImmap\fR\|(2) and data copied using \fImemcpy\fR\|(3). .TP .B splice \fIsplice\fR\|(2) is used to transfer the data and \fIvmsplice\fR\|(2) to transfer data from user-space to the kernel. .TP .B syslet-rw Use the syslet system calls to make regular read/write asynchronous. .TP .B sg SCSI generic sg v3 I/O. May be either synchronous using the SG_IO ioctl, or if the target is an sg character device, we use \fIread\fR\|(2) and \fIwrite\fR\|(2) for asynchronous I/O. .TP .B null Doesn't transfer any data, just pretends to. Mainly used to exercise \fBfio\fR itself and for debugging and testing purposes. .TP .B net Transfer over the network. \fBfilename\fR must be set appropriately to `\fIhost\fR/\fIport\fR' regardless of data direction. If receiving, only the \fIport\fR argument is used. .TP .B netsplice Like \fBnet\fR, but uses \fIsplice\fR\|(2) and \fIvmsplice\fR\|(2) to map data and send/receive. .TP .B cpuio Doesn't transfer any data, but burns CPU cycles according to \fBcpuload\fR and \fBcpucycles\fR parameters. .TP .B guasi The GUASI I/O engine is the Generic Userspace Asynchronous Syscall Interface approach to asycnronous I/O. .br See . .TP .B external Loads an external I/O engine object file. Append the engine filename as `:\fIenginepath\fR'. .RE .RE .TP .BI iodepth \fR=\fPint Number of I/O units to keep in flight against the file. Default: 1. .TP .BI iodepth_batch \fR=\fPint Number of I/Os to submit at once. Default: \fBiodepth\fR. .TP .BI iodepth_batch_complete \fR=\fPint This defines how many pieces of IO to retrieve at once. It defaults to 1 which means that we'll ask for a minimum of 1 IO in the retrieval process from the kernel. The IO retrieval will go on until we hit the limit set by \fBiodepth_low\fR. If this variable is set to 0, then fio will always check for completed events before queuing more IO. This helps reduce IO latency, at the cost of more retrieval system calls. .TP .BI iodepth_low \fR=\fPint Low watermark indicating when to start filling the queue again. Default: \fBiodepth\fR. .TP .BI direct \fR=\fPbool If true, use non-buffered I/O (usually O_DIRECT). Default: false. .TP .BI buffered \fR=\fPbool If true, use buffered I/O. This is the opposite of the \fBdirect\fR parameter. Default: true. .TP .BI offset \fR=\fPint Offset in the file to start I/O. Data before the offset will not be touched. .TP .BI fsync \fR=\fPint How many I/Os to perform before issuing an \fBfsync\fR\|(2) of dirty data. If 0, don't sync. Default: 0. .TP .BI fdatasync \fR=\fPint Like \fBfsync\fR, but uses \fBfdatasync\fR\|(2) instead to only sync the data parts of the file. Default: 0. .TP .BI overwrite \fR=\fPbool If writing, setup the file first and do overwrites. Default: false. .TP .BI end_fsync \fR=\fPbool Sync file contents when job exits. Default: false. .TP .BI fsync_on_close \fR=\fPbool If true, sync file contents on close. This differs from \fBend_fsync\fR in that it will happen on every close, not just at the end of the job. Default: false. .TP .BI rwmixcycle \fR=\fPint How many milliseconds before switching between reads and writes for a mixed workload. Default: 500ms. .TP .BI rwmixread \fR=\fPint Percentage of a mixed workload that should be reads. Default: 50. .TP .BI rwmixwrite \fR=\fPint Percentage of a mixed workload that should be writes. If \fBrwmixread\fR and \fBrwmixwrite\fR are given and do not sum to 100%, the latter of the two overrides the first. This may interfere with a given rate setting, if fio is asked to limit reads or writes to a certain rate. If that is the case, then the distribution may be skewed. Default: 50. .TP .B norandommap Normally \fBfio\fR will cover every block of the file when doing random I/O. If this parameter is given, a new offset will be chosen without looking at past I/O history. This parameter is mutually exclusive with \fBverify\fR. .TP .B softrandommap See \fBnorandommap\fR. If fio runs with the random block map enabled and it 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 nice \fR=\fPint Run job with given nice value. See \fInice\fR\|(2). .TP .BI prio \fR=\fPint Set I/O priority value of this job between 0 (highest) and 7 (lowest). See \fIionice\fR\|(1). .TP .BI prioclass \fR=\fPint Set I/O priority class. See \fIionice\fR\|(1). .TP .BI thinktime \fR=\fPint Stall job for given number of microseconds between issuing I/Os. .TP .BI thinktime_spin \fR=\fPint Pretend to spend CPU time for given number of microseconds, sleeping the rest of the time specified by \fBthinktime\fR. Only valid if \fBthinktime\fR is set. .TP .BI thinktime_blocks \fR=\fPint Number of blocks to issue before waiting \fBthinktime\fR microseconds. Default: 1. .TP .BI rate \fR=\fPint Cap bandwidth used by this job. The number is in bytes/sec, the normal postfix rules apply. You can use \fBrate\fR=500k to limit reads and writes to 500k each, or you can specify read and writes separately. Using \fBrate\fR=1m,500k would limit reads to 1MB/sec and writes to 500KB/sec. Capping only reads or writes can be done with \fBrate\fR=,500k or \fBrate\fR=500k,. The former will only limit writes (to 500KB/sec), the latter will only limit reads. .TP .BI ratemin \fR=\fPint Tell \fBfio\fR to do whatever it can to maintain at least the given bandwidth. Failing to meet this requirement will cause the job to exit. The same format as \fBrate\fR is used for read vs write separation. .TP .BI rate_iops \fR=\fPint Cap the bandwidth to this number of IOPS. Basically the same as rate, just specified independently of bandwidth. The same format as \fBrate\fR is used for read vs write seperation. If \fBblocksize\fR is a range, the smallest block size is used as the metric. .TP .BI rate_iops_min \fR=\fPint If this rate of I/O is not met, the job will exit. The same format as \fBrate\fR is used for read vs write seperation. .TP .BI ratecycle \fR=\fPint Average bandwidth for \fBrate\fR and \fBratemin\fR over this number of milliseconds. Default: 1000ms. .TP .BI cpumask \fR=\fPint Set CPU affinity for this job. \fIint\fR is a bitmask of allowed CPUs the job may run on. See \fBsched_setaffinity\fR\|(2). .TP .BI cpus_allowed \fR=\fPstr Same as \fBcpumask\fR, but allows a comma-delimited list of CPU numbers. .TP .BI startdelay \fR=\fPint Delay start of job for the specified number of seconds. .TP .BI runtime \fR=\fPint Terminate processing after the specified number of seconds. .TP .B time_based If given, run for the specified \fBruntime\fR duration even if the files are completely read or written. The same workload will be repeated as many times as \fBruntime\fR allows. .TP .BI ramp_time \fR=\fPint If set, fio will run the specified workload for this amount of time before logging any performance numbers. Useful for letting performance settle before logging results, thus minimizing the runtime required for stable results. Note that the \fBramp_time\fR is considered lead in time for a job, thus it will increase the total runtime if a special timeout or runtime is specified. .TP .BI invalidate \fR=\fPbool Invalidate buffer-cache for the file prior to starting I/O. Default: true. .TP .BI sync \fR=\fPbool Use synchronous I/O for buffered writes. For the majority of I/O engines, this means using O_SYNC. Default: false. .TP .BI iomem \fR=\fPstr "\fR,\fP mem" \fR=\fPstr Allocation method for I/O unit buffer. Allowed values are: .RS .RS .TP .B malloc Allocate memory with \fImalloc\fR\|(3). .TP .B shm Use shared memory buffers allocated through \fIshmget\fR\|(2). .TP .B shmhuge Same as \fBshm\fR, but use huge pages as backing. .TP .B mmap Use \fImmap\fR\|(2) for allocation. Uses anonymous memory unless a filename is given after the option in the format `:\fIfile\fR'. .TP .B mmaphuge Same as \fBmmap\fR, but use huge files as backing. .RE .P The amount of memory allocated is the maximum allowed \fBblocksize\fR for the job multiplied by \fBiodepth\fR. For \fBshmhuge\fR or \fBmmaphuge\fR to work, the system must have free huge pages allocated. \fBmmaphuge\fR also needs to have hugetlbfs mounted, and \fIfile\fR must point there. At least on Linux, huge pages must be manually allocated. See \fB/proc/sys/vm/nr_hugehages\fR and the documentation for that. Normally you just need to echo an appropriate number, eg echoing 8 will ensure that the OS has 8 huge pages ready for use. .RE .TP .BI iomem_align \fR=\fPint This indiciates the memory alignment of the IO memory buffers. Note that the given alignment is applied to the first IO unit buffer, if using \fBiodepth\fR the alignment of the following buffers are given by the \fBbs\fR used. In other words, if using a \fBbs\fR that is a multiple of the page sized in the system, all buffers will be aligned to this value. If using a \fBbs\fR that is not page aligned, the alignment of subsequent IO memory buffers is the sum of the \fBiomem_align\fR and \fBbs\fR used. .TP .BI hugepage\-size \fR=\fPint Defines the size of a huge page. Must be at least equal to the system setting. Should be a multiple of 1MB. Default: 4MB. .TP .B exitall Terminate all jobs when one finishes. Default: wait for each job to finish. .TP .BI bwavgtime \fR=\fPint Average bandwidth calculations over the given time in milliseconds. Default: 500ms. .TP .BI create_serialize \fR=\fPbool If true, serialize file creation for the jobs. Default: true. .TP .BI create_fsync \fR=\fPbool \fIfsync\fR\|(2) data file after creation. Default: true. .TP .BI create_on_open \fR=\fPbool If true, the files are not created until they are opened for IO by the job. .TP .BI pre_read \fR=\fPbool If this is given, files will be pre-read into memory before starting the given IO operation. This will also clear the \fR \fBinvalidate\fR flag, since it is pointless to pre-read and then drop the cache. This will only work for IO engines that are seekable, since they allow you to read the same data multiple times. Thus it will not work on eg network or splice IO. .TP .BI unlink \fR=\fPbool Unlink job files when done. Default: false. .TP .BI loops \fR=\fPint Specifies the number of iterations (runs of the same workload) of this job. Default: 1. .TP .BI do_verify \fR=\fPbool Run the verify phase after a write phase. Only valid if \fBverify\fR is set. Default: true. .TP .BI verify \fR=\fPstr Method of verifying file contents after each iteration of the job. Allowed values are: .RS .RS .TP .B md5 crc16 crc32 crc32c crc32c-intel crc64 crc7 sha256 sha512 sha1 Store appropriate checksum in the header of each block. .TP .B meta Write extra information about each I/O (timestamp, block number, etc.). The block number is verified. .TP .B pattern Fill I/O buffers with a specific pattern that is used to verify. If the pattern is < 4bytes, it can either be a decimal or a hexadecimal number. If the pattern is > 4bytes, currently, it can only be a hexadecimal pattern starting with either "0x" or "0X". .TP .B null Pretend to verify. Used for testing internals. .RE 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. If the data direction given is a read or random read, fio will assume that it should verify a previously written file. If the data direction includes any form of write, the verify will be of the newly written data. .RE .TP .BI verify_sort \fR=\fPbool If true, written verify blocks are sorted if \fBfio\fR deems it to be faster to read them back in a sorted manner. Default: true. .TP .BI verify_offset \fR=\fPint Swap the verification header with data somewhere else in the block before writing. It is swapped back before verifying. .TP .BI verify_interval \fR=\fPint Write the verification header for this number of bytes, which should divide \fBblocksize\fR. Default: \fBblocksize\fR. .TP .BI verify_fatal \fR=\fPbool If true, exit the job on the first observed verification failure. Default: false. .TP .BI verify_async \fR=\fPint Fio will normally verify IO inline from the submitting thread. This option takes an integer describing how many async offload threads to create for IO verification instead, causing fio to offload the duty of verifying IO contents to one or more separate threads. If using this offload option, even sync IO engines can benefit from using an \fBiodepth\fR setting higher than 1, as it allows them to have IO in flight while verifies are running. .TP .BI verify_async_cpus \fR=\fPstr Tell fio to set the given CPU affinity on the async IO verification threads. See \fBcpus_allowed\fP for the format used. .TP .B stonewall Wait for preceeding jobs in the job file to exit before starting this one. \fBstonewall\fR implies \fBnew_group\fR. .TP .B new_group Start a new reporting group. If not given, all jobs in a file will be part of the same reporting group, unless separated by a stonewall. .TP .BI numjobs \fR=\fPint Number of clones (processes/threads performing the same workload) of this job. Default: 1. .TP .B group_reporting If set, display per-group reports instead of per-job when \fBnumjobs\fR is specified. .TP .B thread Use threads created with \fBpthread_create\fR\|(3) instead of processes created with \fBfork\fR\|(2). .TP .BI zonesize \fR=\fPint Divide file into zones of the specified size in bytes. See \fBzoneskip\fR. .TP .BI zoneskip \fR=\fPint Skip the specified number of bytes when \fBzonesize\fR bytes of data have been read. .TP .BI write_iolog \fR=\fPstr Write the issued I/O patterns to the specified file. .TP .BI read_iolog \fR=\fPstr Replay the I/O patterns contained in the specified file generated by \fBwrite_iolog\fR, or may be a \fBblktrace\fR binary file. .TP .B write_bw_log \fR=\fPstr 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. The included fio_generate_plots script uses gnuplot to turn these text files into nice graphs. See \fBwrite_log_log\fR for behaviour of given filename. For this option, the postfix is _bw.log. .TP .B write_lat_log Same as \fBwrite_bw_log\fR, but writes I/O completion latencies. If no filename is given with this option, the default filename of "jobname_type.log" is used. Even if the filename is given, fio will still append the type of log. .TP .B disable_clat \fR=\fPbool Disable measurements of completion latency numbers. Useful only for cutting back the number of calls to gettimeofday, as that does impact performance at really high IOPS rates. Note that to really get rid of a large amount of these calls, this option must be used with disable_slat and disable_bw as well. .TP .B disable_slat \fR=\fPbool Disable measurements of submission latency numbers. See \fBdisable_clat\fR. .TP .B disable_bw_measurement \fR=\fPbool Disable measurements of throughput/bandwidth numbers. See \fBdisable_clat\fR. .TP .BI lockmem \fR=\fPint Pin the specified amount of memory with \fBmlock\fR\|(2). Can be used to simulate a smaller amount of memory. .TP .BI exec_prerun \fR=\fPstr Before running the job, execute the specified command with \fBsystem\fR\|(3). .TP .BI exec_postrun \fR=\fPstr Same as \fBexec_prerun\fR, but the command is executed after the job completes. .TP .BI ioscheduler \fR=\fPstr Attempt to switch the device hosting the file to the specified I/O scheduler. .TP .BI cpuload \fR=\fPint If the job is a CPU cycle-eater, attempt to use the specified percentage of CPU cycles. .TP .BI cpuchunks \fR=\fPint If the job is a CPU cycle-eater, split the load into cycles of the given time in milliseconds. .TP .BI disk_util \fR=\fPbool Generate disk utilization statistics if the platform supports it. Default: true. .TP .BI gtod_reduce \fR=\fPbool Enable all of the gettimeofday() reducing options (disable_clat, disable_slat, disable_bw) plus reduce precision of the timeout somewhat to really shrink the gettimeofday() call count. With this option enabled, we only do about 0.4% of the gtod() calls we would have done if all time keeping was enabled. .TP .BI gtod_cpu \fR=\fPint Sometimes it's cheaper to dedicate a single thread of execution to just getting the current time. Fio (and databases, for instance) are very intensive on gettimeofday() calls. With this option, you can set one CPU aside for doing nothing but logging current time to a shared memory location. Then the other threads/processes that run IO workloads need only copy that segment, instead of entering the kernel with a gettimeofday() call. The CPU set aside for doing these time calls will be excluded from other uses. Fio will manually clear it from the CPU mask of other jobs. .TP .BI cgroup \fR=\fPstr Add job to this control group. If it doesn't exist, it will be created. The system must have a mounted cgroup blkio mount point for this to work. If your system doesn't have it mounted, you can do so with: # mount -t cgroup -o blkio none /cgroup .TP .BI cgroup_weight \fR=\fPint Set the weight of the cgroup to this value. See the documentation that comes with the kernel, allowed values are in the range of 100..1000. .TP .BI uid \fR=\fPint Instead of running as the invoking user, set the user ID to this value before the thread/process does any work. .TP .BI gid \fR=\fPint Set group ID, see \fBuid\fR. .SH OUTPUT While running, \fBfio\fR will display the status of the created jobs. For example: .RS .P Threads: 1: [_r] [24.8% done] [ 13509/ 8334 kb/s] [eta 00h:01m:31s] .RE .P The characters in the first set of brackets denote the current status of each threads. The possible values are: .P .PD 0 .RS .TP .B P Setup but not started. .TP .B C Thread created. .TP .B I Initialized, waiting. .TP .B R Running, doing sequential reads. .TP .B r Running, doing random reads. .TP .B W Running, doing sequential writes. .TP .B w Running, doing random writes. .TP .B M Running, doing mixed sequential reads/writes. .TP .B m Running, doing mixed random reads/writes. .TP .B F Running, currently waiting for \fBfsync\fR\|(2). .TP .B V Running, verifying written data. .TP .B E Exited, not reaped by main thread. .TP .B \- Exited, thread reaped. .RE .PD .P The second set of brackets shows the estimated completion percentage of the current group. The third set shows the read and write I/O rate, respectively. Finally, the estimated run time of the job is displayed. .P When \fBfio\fR completes (or is interrupted by Ctrl-C), it will show data for each thread, each group of threads, and each disk, in that order. .P Per-thread statistics first show the threads client number, group-id, and error code. The remaining figures are as follows: .RS .TP .B io Number of megabytes of I/O performed. .TP .B bw Average data rate (bandwidth). .TP .B runt Threads run time. .TP .B slat Submission latency minimum, maximum, average and standard deviation. This is the time it took to submit the I/O. .TP .B clat Completion latency minimum, maximum, average and standard deviation. This is the time between submission and completion. .TP .B bw Bandwidth minimum, maximum, percentage of aggregate bandwidth received, average and standard deviation. .TP .B cpu CPU usage statistics. Includes user and system time, number of context switches this thread went through and number of major and minor page faults. .TP .B IO depths Distribution of I/O depths. Each depth includes everything less than (or equal) to it, but greater than the previous depth. .TP .B IO issued Number of read/write requests issued, and number of short read/write requests. .TP .B IO latencies Distribution of I/O completion latencies. The numbers follow the same pattern as \fBIO depths\fR. .RE .P The group statistics show: .PD 0 .RS .TP .B io Number of megabytes I/O performed. .TP .B aggrb Aggregate bandwidth of threads in the group. .TP .B minb Minimum average bandwidth a thread saw. .TP .B maxb Maximum average bandwidth a thread saw. .TP .B mint Shortest runtime of threads in the group. .TP .B maxt Longest runtime of threads in the group. .RE .PD .P Finally, disk statistics are printed with reads first: .PD 0 .RS .TP .B ios Number of I/Os performed by all groups. .TP .B merge Number of merges in the I/O scheduler. .TP .B ticks Number of ticks we kept the disk busy. .TP .B io_queue Total time spent in the disk queue. .TP .B util Disk utilization. .RE .PD .SH TERSE OUTPUT If the \fB\-\-minimal\fR option is given, the results will be printed in a semicolon-delimited format suitable for scripted use. The fields are: .P .RS .B jobname, groupid, error .P Read status: .RS .B KB I/O, bandwidth \fR(KB/s)\fP, runtime \fR(ms)\fP .P Submission latency: .RS .B min, max, mean, standard deviation .RE Completion latency: .RS .B min, max, mean, standard deviation .RE Bandwidth: .RS .B min, max, aggregate percentage of total, mean, standard deviation .RE .RE .P Write status: .RS .B KB I/O, bandwidth \fR(KB/s)\fP, runtime \fR(ms)\fP .P Submission latency: .RS .B min, max, mean, standard deviation .RE Completion latency: .RS .B min, max, mean, standard deviation .RE Bandwidth: .RS .B min, max, aggregate percentage of total, mean, standard deviation .RE .RE .P CPU usage: .RS .B user, system, context switches, major page faults, minor page faults .RE .P IO depth distribution: .RS .B <=1, 2, 4, 8, 16, 32, >=64 .RE .P IO latency distribution (ms): .RS .B <=2, 4, 10, 20, 50, 100, 250, 500, 750, 1000, >=2000 .RE .P .B text description .RE .SH AUTHORS .B fio was written by Jens Axboe . .br This man page was written by Aaron Carroll based on documentation by Jens Axboe. .SH "REPORTING BUGS" Report bugs to the \fBfio\fR mailing list . See \fBREADME\fR. .SH "SEE ALSO" For further documentation see \fBHOWTO\fR and \fBREADME\fR. .br Sample jobfiles are available in the \fBexamples\fR directory.