X-Git-Url: https://git.kernel.dk/?p=fio.git;a=blobdiff_plain;f=HOWTO;h=12974f3f4dcc563cd143a1084aaff17116d70d48;hp=460b456ce44b312a016346a62c30a7a8093bb86b;hb=44c47feb9edc7854bf3cfa2e3d843e90fc969b3a;hpb=d3aad8f28b9e214fccfce5e3a406dec723f57a62 diff --git a/HOWTO b/HOWTO index 460b456c..12974f3f 100644 --- a/HOWTO +++ b/HOWTO @@ -170,7 +170,8 @@ 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. If prefixed with + 0x, the integer is assumed to be of base 16 (hexidecimal). 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, @@ -211,11 +212,32 @@ 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. +lockfile=str Fio defaults to not doing any locking 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: + + none No locking. The default. + exclusive Only one thread/process may do IO, + excluding all others. + readwrite Read-write locking on the file. Many + readers may access the file at the + same time, but writes get exclusive + access. + + 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 acqusition is + expensive, batching the lock/unlocks will speed up IO. + readwrite=str rw=str Type of io pattern. Accepted values are: @@ -228,23 +250,41 @@ rw=str Type of io pattern. Accepted values are: For the mixed io types, the default is to split them 50/50. For certain types of io the result may still be skewed a bit, - since the speed may be different. + since the speed may be different. It is possible to specify + a number of IO's to do before getting a new offset - this + is only useful for random IO, where fio would normally + generate a new random offset for every IO. If you append + eg 8 to randread, you would get a new random offset for + every 8 IO's. The result would be a seek for only every 8 + IO's, instead of for every IO. Use rw=randread:8 to specify + that. 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 and limited to 'size' in total (if that is given). If not given, each created file is the same size. +fill_device=bool 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. + blocksize=siint 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 @@ -264,11 +304,44 @@ bsrange=irange Instead of giving a single block size, specify a range writes, however a second range can be given after a comma. See bs=. +bssplit=str Sometimes you want even finer grained control of the + block sizes issued, not just an even split between them. + This option allows you to weight various block sizes, + so that you are able to define a specific amount of + block sizes issued. The format for this option is: + + bssplit=blocksize/percentage:blocksize/percentage + + for as many block sizes as needed. So if you want to define + a workload that has 50% 64k blocks, 10% 4k blocks, and + 40% 32k blocks, you would write: + + bssplit=4k/10:64k/50:32k/40 + + Ordering does not matter. If the percentage is left blank, + fio will fill in the remaining values evenly. So a bssplit + option like this one: + + bssplit=4k/50:1k/:32k/ + + would have 50% 4k ios, and 25% 1k and 32k ios. The percentages + always add up to 100, if bssplit is given a range that adds + up to more, it will error out. + blocksize_unaligned 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. + +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. + 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 @@ -294,10 +367,16 @@ ioengine=str Defines how the job issues io to the file. The following sync Basic read(2) or write(2) io. lseek(2) is used to position the io location. + psync Basic pread(2) or pwrite(2) io. + + vsync Basic readv(2) or writev(2) IO. + libaio Linux native asynchronous io. posixaio glibc posix asynchronous io. + solarisaio Solaris native asynchronous io. + mmap File is memory mapped and data copied to/from using memcpy(3). @@ -324,11 +403,25 @@ ioengine=str Defines how the job issues io to the file. The following or receive, if the latter only the port argument is used. - cpu Doesn't transfer any data, but burns CPU + netsplice Like net, but uses splice/vmsplice to + map data and send/receive. + + cpuio Doesn't transfer any data, but burns CPU cycles according to the cpuload= and cpucycle= options. Setting cpuload=85 will cause that job to do nothing but burn - 85% of the CPU. + 85% of the CPU. In case of SMP machines, + use numjobs= to get desired CPU + usage, as the cpuload only loads a single + CPU at the desired rate. + + guasi The GUASI IO engine is the Generic Userspace + Asyncronous Syscall Interface approach + to async IO. See + + http://www.xmailserver.org/guasi-lib.html + + for more info on GUASI. external Prefix to specify loading an external IO engine object file. Append the engine @@ -341,8 +434,9 @@ iodepth=int This defines how many io units to keep in flight against 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. + It defaults to 1 which means that we submit each IO + as soon as it is available, but can be raised to submit + bigger batches of IO at the time. iodepth_low=int The low water mark indicating when to start filling the queue again. Defaults to the same as iodepth, meaning @@ -368,7 +462,11 @@ fsync=int If writing to a file, issue a sync of the dirty data not sync the file. The exception is the sg io engine, which synchronizes the disk cache anyway. -overwrite=bool If writing to a file, setup the file first and do overwrites. +overwrite=bool If true, writes to a file will always overwrite existing + data. If the file doesn't already exist, it will be + created before the write phase begins. If the file exists + and is large enough for the specified write phase, nothing + will be done. end_fsync=bool If true, fsync file contents when the job exits. @@ -376,10 +474,6 @@ fsync_on_close=bool If true, fio will fsync() a dirty file on close. This differs from end_fsync in that it will happen on every file close, not just at the end of the job. -rwmixcycle=int Value in milliseconds describing how often to switch between - reads and writes for a mixed workload. The default is - 500 msecs. - rwmixread=int How large a percentage of the mix should be reads. rwmixwrite=int How large a percentage of the mix should be writes. If both @@ -392,7 +486,15 @@ 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. + +softrandommap See norandommap. 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. nice=int Run the job with the given nice value. See man nice(2). @@ -437,8 +539,15 @@ ratecycle=int Average bandwidth for 'rate' and 'ratemin' over this number 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 - sched_setaffinity(2). + bitmask of allowed CPU's the job may run on. So if you want + the allowed CPUs to be 1 and 5, you would pass the decimal + value of (1 << 1 | 1 << 5), or 34. See man + sched_setaffinity(2). This may not work on all supported + operating systems or kernel versions. + +cpus_allowed=str Controls the same options as cpumask, but it allows a text + setting of the permitted CPUs instead. So to use CPUs 1 and + 5, you would specify cpus_allowed=1,5. startdelay=int Start this job the specified number of seconds after fio has started. Only useful if the job file contains several @@ -450,6 +559,11 @@ 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. @@ -524,22 +638,83 @@ loops=int Run the specified number of iterations of this job. Used to repeat the same workload a given number of times. Defaults to 1. +do_verify=bool Run the verify phase after a write phase. Only makes sense if + verify is set. Defaults to 1. + verify=str If writing to a file, fio can verify the file contents after each iteration of the job. The allowed values are: md5 Use an md5 sum of the data area and store it in the header of each block. + crc64 Use an experimental crc64 sum of the data + area and store it in the header of each + block. + crc32 Use a crc32 sum of the data area and store it in the header of each block. + crc16 Use a crc16 sum of the data area and store + it in the header of each block. + + crc7 Use a crc7 sum of the data area and store + it in the header of each block. + + sha512 Use sha512 as the checksum function. + + sha256 Use sha256 as the checksum function. + + meta Write extra information about each io + (timestamp, block number etc.). The block + number is verified. + + 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. + +verify_offset=siint Swap the verification header with data somewhere else + in the block before writing. Its swapped back before + verifying. + +verify_interval=siint Write the verification header at a finer granularity + than the blocksize. It will be written for chunks the + size of header_interval. blocksize should divide this + evenly. + +verify_pattern=int If set, fio will fill the io buffers with this + pattern. Fio defaults to filling with totally random + bytes, but sometimes it's interesting to fill with a known + pattern for io verification purposes. Depending on the + width of the pattern, fio will fill 1/2/3/4 bytes of the + buffer at the time. The verify_pattern cannot be larger than + a 32-bit quantity. + +verify_fatal=bool Normally fio will keep checking the entire contents + before quitting on a block verification failure. If this + option is set, fio will exit the job on the first observed + failure. + 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. + points in the job file. A stone wall also implies starting + a new reporting group. + +new_group Start a new reporting group. If this option isn't given, + jobs in a file will be part of the same reporting group + unless seperated by a stone wall (or if it's a group + by itself, with the numjobs option). numjobs=int Create the specified number of clones of this job. May be used to setup a larger number of threads/processes doing @@ -568,7 +743,12 @@ 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 @@ -598,6 +778,9 @@ 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 --------------------------- @@ -627,9 +810,10 @@ 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, 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). +currently running and doing io, rate of io since last check (read speed +listed first, then write speed), 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 @@ -640,8 +824,11 @@ Client1 (g=0): err= 0: 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 + cpu : usr=1.49%, sys=0.25%, ctx=7969, majf=0, minf=17 IO depths : 1=0.1%, 2=0.3%, 4=0.5%, 8=99.0%, 16=0.0%, 32=0.0%, >32=0.0% + submit : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0% + complete : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=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% @@ -652,10 +839,13 @@ they denote: io= Number of megabytes io performed bw= Average bandwidth rate runt= The runtime of that thread - slat= Submission latency (avg being the average, dev being the + slat= Submission latency (avg being the average, stdev being the standard deviation). This is the time it took to submit the io. For sync io, the slat is really the completion - latency, since queue/complete is one operation there. + latency, since queue/complete is one operation there. This + value can be in miliseconds or microseconds, fio will choose + the most appropriate base and print that. In the example + above, miliseconds is the best scale. clat= Completion latency. Same names as slat, this denotes the time from submission to completion of the io pieces. For sync io, clat will usually be equal (or very close) to 0, @@ -667,12 +857,21 @@ runt= The runtime of that thread only really useful if the threads in this group are on the 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. + of context switches this thread went through, usage of + system and user time, and finally the number of major + and minor page faults. 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 submit= How many pieces of IO were submitting in a single submit + call. Each entry denotes that amount and below, until + the previous entry - eg, 8=100% mean that we submitted + anywhere in between 5-8 ios per submit call. +IO complete= Like the above submit number, but for completions instead. +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, @@ -735,7 +934,7 @@ Split up, the format is as follows: Submission latency: min, max, mean, deviation Completion latency: min, max, mean, deviation Bw: min, max, aggregate percentage of total, mean, deviation - CPU usage: user, system, context switches + CPU usage: user, system, context switches, major faults, minor faults IO depths: <=1, 2, 4, 8, 16, 32, >=64 IO latencies: <=2, 4, 10, 20, 50, 100, 250, 500, 750, 1000, >=2000 Text description