4 fio is a tool that will spawn a number of thread doing a particular
5 type of io action as specified by the user. fio takes a number of
6 global parameters, each inherited by the thread unless otherwise
7 parameters given to them overriding that setting is given.
13 fio resides in a git repo, the canonical place is:
15 git://brick.kernel.dk/data/git/fio.git
17 Snapshots are frequently generated as well and they include the git
18 meta data as well. You can download them here:
20 http://brick.kernel.dk/snaps/
28 -b block size in KiB for each io
29 -t <sec> Runtime in seconds
30 -r For random io, sequence must be repeatable
31 -R <on> If one thread fails to meet rate, quit all
32 -o <on> Use direct IO is 1, buffered if 0
33 -l Generate per-job latency logs
34 -w Generate per-job bandwidth logs
35 -f <file> Read <file> for job descriptions
37 -v Print version information and exit
39 The <jobs> format is as follows:
41 directory=x Use 'x' as the top level directory for storing files
42 rw=x 'x' may be: read, randread, write, randwrite,
43 rw (read-write mix), randrw (read-write random mix)
44 size=x Set file size to x bytes (x string can include k/m/g)
45 ioengine=x 'x' may be: aio/libaio/linuxaio for Linux aio,
46 posixaio for POSIX aio, sync for regular read/write io,
47 mmap for mmap'ed io, or sgio for direct SG_IO io. The
48 latter only works on Linux on SCSI (or SCSI-like
49 devices, such as usb-storage or sata/libata driven)
51 iodepth=x For async io, allow 'x' ios in flight
52 overwrite=x If 'x', layout a write file first.
53 prio=x Run io at prio X, 0-7 is the kernel allowed range
54 prioclass=x Run io at prio class X
55 bs=x Use 'x' for thread blocksize. May include k/m postfix.
56 bsrange=x-y Mix thread block sizes randomly between x and y. May
57 also include k/m postfix.
58 direct=x 1 for direct IO, 0 for buffered IO
59 thinktime=x "Think" x usec after each io
60 rate=x Throttle rate to x KiB/sec
61 ratemin=x Quit if rate of x KiB/sec can't be met
62 ratecycle=x ratemin averaged over x msecs
63 cpumask=x Only allow job to run on CPUs defined by mask.
64 fsync=x If writing, fsync after every x blocks have been written
65 startdelay=x Start this thread x seconds after startup
66 timeout=x Terminate x seconds after startup
67 offset=x Start io at offset x (x string can include k/m/g)
68 invalidate=x Invalidate page cache for file prior to doing io
69 sync=x Use sync writes if x and writing
70 mem=x If x == malloc, use malloc for buffers. If x == shm,
71 use shm for buffers. If x == mmap, use anon mmap.
72 exitall When one thread quits, terminate the others
73 bwavgtime=x Average bandwidth stats over an x msec window.
74 create_serialize=x If 'x', serialize file creation.
75 create_fsync=x If 'x', run fsync() after file creation.
76 loops=x Run the job 'x' number of times.
77 verify=x If 'x' == md5, use md5 for verifies. If 'x' == crc32,
78 use crc32 for verifies. md5 is 'safer', but crc32 is
79 a lot faster. Only makes sense for writing to a file.
80 stonewall Wait for preceeding jobs to end before running.
81 numjobs=x Create 'x' similar entries for this job
82 thread Use pthreads instead of forked jobs
84 zoneskip=y Zone options must be paired. If given, the job
85 will skip y bytes for every x read/written. This
86 can be used to gauge hard drive speed over the entire
87 platter, without reading everything. Both x/y can
91 Examples using a job file
92 -------------------------
94 A sample job file doing the same as above would look like this:
104 And fio would be invoked as:
106 $ fio -o1 -s -f file_with_above
108 The second example would look like this:
123 And fio would be invoked as:
125 $ fio -o0 -s -b4096 -f file_with_above
127 'global' is a reserved keyword. When used as the filename, it sets the
128 default options for the threads following that section. It is possible
129 to have more than one global section in the file, as it only affects
132 Also see the examples/ dir for sample job files.
135 Interpreting the output
136 -----------------------
138 fio spits out a lot of output. While running, fio will display the
139 status of the jobs created. An example of that would be:
141 Threads now running: 2 : [ww] [5.73% done]
143 The characters inside the square brackets denote the current status of
144 each thread. The possible values (in typical life cycle order) are:
148 P Thread setup, but not started.
149 C Thread created and running, but not doing anything yet
150 R Running, doing sequential reads.
151 r Running, doing random reads.
152 W Running, doing sequential writes.
153 w Running, doing random writes.
154 V Running, doing verification of written data.
155 E Thread exited, not reaped by main thread yet.
158 The other values are fairly self explanatory - number of thread currently
159 running and doing io, and the estimated completion percentage.
161 When fio is done (or interrupted by ctrl-c), it will show the data for
162 each thread, group of threads, and disks in that order. For each data
163 direction, the output looks like:
165 Client1 (g=0): err= 0:
166 write: io= 32MiB, bw= 666KiB/s, runt= 50320msec
167 slat (msec): min= 0, max= 136, avg= 0.03, dev= 1.92
168 clat (msec): min= 0, max= 631, avg=48.50, dev=86.82
169 bw (KiB/s) : min= 0, max= 1196, per=51.00%, avg=664.02, dev=681.68
170 cpu : usr=1.49%, sys=0.25%, ctx=7969
172 The client number is printed, along with the group id and error of that
173 thread. Below is the io statistics, here for writes. In the order listed,
176 io= Number of megabytes io performed
177 bw= Average bandwidth rate
178 runt= The runtime of that thread
179 slat= Submission latency (avg being the average, dev being the
180 standard deviation). This is the time it took to submit
181 the io. For sync io, the slat is really the completion
182 latency, since queue/complete is one operation there.
183 clat= Completion latency. Same names as slat, this denotes the
184 time from submission to completion of the io pieces. For
185 sync io, clat will usually be equal (or very close) to 0,
186 as the time from submit to complete is basically just
187 CPU time (io has already been done, see slat explanation).
188 bw= Bandwidth. Same names as the xlat stats, but also includes
189 an approximate percentage of total aggregate bandwidth
190 this thread received in this group. This last value is
191 only really useful if the threads in this group are on the
192 same disk, since they are then competing for disk access.
193 cpu= CPU usage. User and system time, along with the number
194 of context switches this thread went through.
196 After each client has been listed, the group statistics are printed. They
199 Run status group 0 (all jobs):
200 READ: io=64MiB, aggrb=22178, minb=11355, maxb=11814, mint=2840msec, maxt=2955msec
201 WRITE: io=64MiB, aggrb=1302, minb=666, maxb=669, mint=50093msec, maxt=50320msec
203 For each data direction, it prints:
205 io= Number of megabytes io performed.
206 aggrb= Aggregate bandwidth of threads in this group.
207 minb= The minimum average bandwidth a thread saw.
208 maxb= The maximum average bandwidth a thread saw.
209 mint= The minimum runtime of a thread.
210 maxt= The maximum runtime of a thread.
212 And finally, the disk statistics are printed. They will look like this:
214 Disk stats (read/write):
215 sda: ios=16398/16511, merge=30/162, ticks=6853/819634, in_queue=826487, util=100.00%
217 Each value is printed for both reads and writes, with reads first. The
220 ios= Number of ios performed by all groups.
221 merge= Number of merges io the io scheduler.
222 ticks= Number of ticks we kept the disk busy.
223 io_queue= Total time spent in the disk queue.
224 util= The disk utilization. A value of 100% means we kept the disk
225 busy constantly, 50% would be a disk idling half of the time.