| fio |
| --- |
| |
| fio is a tool that will spawn a number of thread doing a particular |
| type of io action as specified by the user. fio takes a number of |
| global parameters, each inherited by the thread unless otherwise |
| parameters given to them overriding that setting is given. |
| |
| |
| Source |
| ------ |
| |
| fio resides in a git repo, the canonical place is: |
| |
| git://brick.kernel.dk/data/git/fio.git |
| |
| Snapshots are frequently generated as well and they include the git |
| meta data as well. You can download them here: |
| |
| http://brick.kernel.dk/snaps/ |
| |
| |
| Options |
| ------- |
| |
| $ fio |
| -s IO is sequential |
| -b block size in KiB for each io |
| -t <sec> Runtime in seconds |
| -r For random io, sequence must be repeatable |
| -R <on> If one thread fails to meet rate, quit all |
| -o <on> Use direct IO is 1, buffered if 0 |
| -l Generate per-job latency logs |
| -w Generate per-job bandwidth logs |
| -f <file> Read <file> for job descriptions |
| -h Print help info |
| -v Print version information and exit |
| |
| The <jobs> format is as follows: |
| |
| directory=x Use 'x' as the top level directory for storing files |
| rw=x 'x' may be: read, randread, write, randwrite, |
| rw (read-write mix), randrw (read-write random mix) |
| rwmixcycle=x Base cycle for switching between read and write |
| in msecs. |
| rwmixread=x 'x' percentage of rw mix ios will be reads. If |
| rwmixwrite is also given, the last of the two will |
| be used if they don't add up to 100%. |
| rwmixwrite=x 'x' percentage of rw mix ios will be writes. See |
| rwmixread. |
| size=x Set file size to x bytes (x string can include k/m/g) |
| ioengine=x 'x' may be: aio/libaio/linuxaio for Linux aio, |
| posixaio for POSIX aio, sync for regular read/write io, |
| mmap for mmap'ed io, splice for using splice/vmsplice, |
| or sgio for direct SG_IO io. The latter only works on |
| Linux on SCSI (or SCSI-like devices, such as |
| usb-storage or sata/libata driven) devices. |
| iodepth=x For async io, allow 'x' ios in flight |
| overwrite=x If 'x', layout a write file first. |
| prio=x Run io at prio X, 0-7 is the kernel allowed range |
| prioclass=x Run io at prio class X |
| bs=x Use 'x' for thread blocksize. May include k/m postfix. |
| bsrange=x-y Mix thread block sizes randomly between x and y. May |
| also include k/m postfix. |
| direct=x 1 for direct IO, 0 for buffered IO |
| thinktime=x "Think" x usec after each io |
| rate=x Throttle rate to x KiB/sec |
| ratemin=x Quit if rate of x KiB/sec can't be met |
| ratecycle=x ratemin averaged over x msecs |
| cpumask=x Only allow job to run on CPUs defined by mask. |
| fsync=x If writing, fsync after every x blocks have been written |
| startdelay=x Start this thread x seconds after startup |
| timeout=x Terminate x seconds after startup |
| offset=x Start io at offset x (x string can include k/m/g) |
| invalidate=x Invalidate page cache for file prior to doing io |
| sync=x Use sync writes if x and writing |
| mem=x If x == malloc, use malloc for buffers. If x == shm, |
| use shm for buffers. If x == mmap, use anon mmap. |
| exitall When one thread quits, terminate the others |
| bwavgtime=x Average bandwidth stats over an x msec window. |
| create_serialize=x If 'x', serialize file creation. |
| create_fsync=x If 'x', run fsync() after file creation. |
| end_fsync=x If 'x', run fsync() after end-of-job. |
| loops=x Run the job 'x' number of times. |
| verify=x If 'x' == md5, use md5 for verifies. If 'x' == crc32, |
| use crc32 for verifies. md5 is 'safer', but crc32 is |
| a lot faster. Only makes sense for writing to a file. |
| stonewall Wait for preceeding jobs to end before running. |
| numjobs=x Create 'x' similar entries for this job |
| thread Use pthreads instead of forked jobs |
| zonesize=x |
| zoneskip=y Zone options must be paired. If given, the job |
| will skip y bytes for every x read/written. This |
| can be used to gauge hard drive speed over the entire |
| platter, without reading everything. Both x/y can |
| include k/m/g suffix. |
| iolog=x Open and read io pattern from file 'x'. The file must |
| contain one io action per line in the following format: |
| rw, offset, length |
| where with rw=0/1 for read/write, and the offset |
| and length entries being in bytes. |
| write_iolog=x Write an iolog to file 'x' in the same format as iolog. |
| The iolog options are exclusive, if both given the |
| read iolog will be performed. |
| lockmem=x Lock down x amount of memory on the machine, to |
| simulate a machine with less memory available. x can |
| include k/m/g suffix. |
| nice=x Run job at given nice value. |
| |
| Examples using a job file |
| ------------------------- |
| |
| A sample job file doing the same as above would look like this: |
| |
| [read_file] |
| rw=0 |
| bs=4096 |
| |
| [write_file] |
| rw=1 |
| bs=16384 |
| |
| And fio would be invoked as: |
| |
| $ fio -o1 -s -f file_with_above |
| |
| The second example would look like this: |
| |
| [rf1] |
| rw=0 |
| prio=6 |
| |
| [rf2] |
| rw=0 |
| prio=3 |
| |
| [rf3] |
| rw=0 |
| prio=0 |
| direct=1 |
| |
| And fio would be invoked as: |
| |
| $ fio -o0 -s -b4096 -f file_with_above |
| |
| 'global' is a reserved keyword. When used as the filename, it sets the |
| default options for the threads following that section. It is possible |
| to have more than one global section in the file, as it only affects |
| subsequent jobs. |
| |
| Also see the examples/ dir for sample job files. |
| |
| |
| Interpreting the output |
| ----------------------- |
| |
| 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 now running: 2 : [ww] [5.73% done] |
| |
| The characters inside the square brackets denote the current status of |
| each thread. The possible values (in typical life cycle order) are: |
| |
| Idle Run |
| ---- --- |
| P Thread setup, but not started. |
| C Thread created and running, but not doing anything yet |
| R Running, doing sequential reads. |
| r Running, doing random reads. |
| W Running, doing sequential writes. |
| w Running, doing random writes. |
| V Running, doing verification of written data. |
| E Thread exited, not reaped by main thread yet. |
| _ Thread reaped. |
| |
| The other values are fairly self explanatory - number of thread currently |
| running and doing io, and the estimated completion percentage. |
| |
| 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 |
| 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 |
| cpu : usr=1.49%, sys=0.25%, ctx=7969 |
| |
| 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, |
| 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 |
| 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. |
| 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, |
| as the time from submit to complete is basically just |
| CPU time (io has already been done, see slat explanation). |
| bw= Bandwidth. Same names as the xlat stats, but also includes |
| an approximate percentage of total aggregate bandwidth |
| this thread received in this group. This last value is |
| 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. |
| |
| After each client has been listed, the group statistics are printed. They |
| will look like this: |
| |
| Run status group 0 (all jobs): |
| READ: io=64MiB, aggrb=22178, minb=11355, maxb=11814, mint=2840msec, maxt=2955msec |
| WRITE: io=64MiB, aggrb=1302, minb=666, maxb=669, mint=50093msec, maxt=50320msec |
| |
| For each data direction, it prints: |
| |
| io= Number of megabytes io performed. |
| aggrb= Aggregate bandwidth of threads in this group. |
| minb= The minimum average bandwidth a thread saw. |
| maxb= The maximum average bandwidth a thread saw. |
| mint= The minimum runtime of a thread. |
| maxt= The maximum runtime of a thread. |
| |
| And finally, the disk statistics are printed. They will look like this: |
| |
| Disk stats (read/write): |
| sda: ios=16398/16511, merge=30/162, ticks=6853/819634, in_queue=826487, util=100.00% |
| |
| Each value is printed for both reads and writes, with reads first. The |
| numbers denote: |
| |
| ios= Number of ios performed by all groups. |
| merge= Number of merges io the io scheduler. |
| ticks= Number of ticks we kept the disk busy. |
| io_queue= Total time spent in the disk queue. |
| util= The disk utilization. A value of 100% means we kept the disk |
| busy constantly, 50% would be a disk idling half of the time. |