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/
22 Pascal Bleser <guru@unixtech.be> has fio RPMs in his repository, you
25 http://linux01.gwdg.de/~pbleser/rpm-navigation.php?cat=System/fio
33 -b block size in KiB for each io
34 -t <sec> Runtime in seconds
35 -r For random io, sequence must be repeatable
36 -R <on> If one thread fails to meet rate, quit all
37 -o <on> Use direct IO is 1, buffered if 0
38 -l Generate per-job latency logs
39 -w Generate per-job bandwidth logs
40 -f <file> Read <file> for job descriptions
42 -v Print version information and exit
44 The <jobs> format is as follows:
46 directory=x Use 'x' as the top level directory for storing files
47 rw=x 'x' may be: read, randread, write, randwrite,
48 rw (read-write mix), randrw (read-write random mix)
49 rwmixcycle=x Base cycle for switching between read and write
51 rwmixread=x 'x' percentage of rw mix ios will be reads. If
52 rwmixwrite is also given, the last of the two will
53 be used if they don't add up to 100%.
54 rwmixwrite=x 'x' percentage of rw mix ios will be writes. See
56 size=x Set file size to x bytes (x string can include k/m/g)
57 ioengine=x 'x' may be: aio/libaio/linuxaio for Linux aio,
58 posixaio for POSIX aio, sync for regular read/write io,
59 mmap for mmap'ed io, splice for using splice/vmsplice,
60 or sgio for direct SG_IO io. The latter only works on
61 Linux on SCSI (or SCSI-like devices, such as
62 usb-storage or sata/libata driven) devices.
63 iodepth=x For async io, allow 'x' ios in flight
64 overwrite=x If 'x', layout a write file first.
65 prio=x Run io at prio X, 0-7 is the kernel allowed range
66 prioclass=x Run io at prio class X
67 bs=x Use 'x' for thread blocksize. May include k/m postfix.
68 bsrange=x-y Mix thread block sizes randomly between x and y. May
69 also include k/m postfix.
70 direct=x 1 for direct IO, 0 for buffered IO
71 thinktime=x "Think" x usec after each io
72 rate=x Throttle rate to x KiB/sec
73 ratemin=x Quit if rate of x KiB/sec can't be met
74 ratecycle=x ratemin averaged over x msecs
75 cpumask=x Only allow job to run on CPUs defined by mask.
76 fsync=x If writing, fsync after every x blocks have been written
77 startdelay=x Start this thread x seconds after startup
78 timeout=x Terminate x seconds after startup
79 offset=x Start io at offset x (x string can include k/m/g)
80 invalidate=x Invalidate page cache for file prior to doing io
81 sync=x Use sync writes if x and writing
82 mem=x If x == malloc, use malloc for buffers. If x == shm,
83 use shm for buffers. If x == mmap, use anon mmap.
84 exitall When one thread quits, terminate the others
85 bwavgtime=x Average bandwidth stats over an x msec window.
86 create_serialize=x If 'x', serialize file creation.
87 create_fsync=x If 'x', run fsync() after file creation.
88 end_fsync=x If 'x', run fsync() after end-of-job.
89 loops=x Run the job 'x' number of times.
90 verify=x If 'x' == md5, use md5 for verifies. If 'x' == crc32,
91 use crc32 for verifies. md5 is 'safer', but crc32 is
92 a lot faster. Only makes sense for writing to a file.
93 stonewall Wait for preceeding jobs to end before running.
94 numjobs=x Create 'x' similar entries for this job
95 thread Use pthreads instead of forked jobs
97 zoneskip=y Zone options must be paired. If given, the job
98 will skip y bytes for every x read/written. This
99 can be used to gauge hard drive speed over the entire
100 platter, without reading everything. Both x/y can
101 include k/m/g suffix.
102 iolog=x Open and read io pattern from file 'x'. The file must
103 contain one io action per line in the following format:
105 where with rw=0/1 for read/write, and the offset
106 and length entries being in bytes.
107 write_iolog=x Write an iolog to file 'x' in the same format as iolog.
108 The iolog options are exclusive, if both given the
109 read iolog will be performed.
110 lockmem=x Lock down x amount of memory on the machine, to
111 simulate a machine with less memory available. x can
112 include k/m/g suffix.
113 nice=x Run job at given nice value.
114 exec_prerun=x Run 'x' before job io is begun.
115 exec_postrun=x Run 'x' after job io has finished.
116 ioscheduler=x Use ioscheduler 'x' for this job.
118 Examples using a job file
119 -------------------------
121 A sample job file doing the same as above would look like this:
131 And fio would be invoked as:
133 $ fio -o1 -s -f file_with_above
135 The second example would look like this:
150 And fio would be invoked as:
152 $ fio -o0 -s -b4096 -f file_with_above
154 'global' is a reserved keyword. When used as the filename, it sets the
155 default options for the threads following that section. It is possible
156 to have more than one global section in the file, as it only affects
159 Also see the examples/ dir for sample job files.
162 Interpreting the output
163 -----------------------
165 fio spits out a lot of output. While running, fio will display the
166 status of the jobs created. An example of that would be:
168 Threads now running: 2 : [ww] [5.73% done]
170 The characters inside the square brackets denote the current status of
171 each thread. The possible values (in typical life cycle order) are:
175 P Thread setup, but not started.
176 C Thread created and running, but not doing anything yet
177 R Running, doing sequential reads.
178 r Running, doing random reads.
179 W Running, doing sequential writes.
180 w Running, doing random writes.
181 V Running, doing verification of written data.
182 E Thread exited, not reaped by main thread yet.
185 The other values are fairly self explanatory - number of thread currently
186 running and doing io, and the estimated completion percentage.
188 When fio is done (or interrupted by ctrl-c), it will show the data for
189 each thread, group of threads, and disks in that order. For each data
190 direction, the output looks like:
192 Client1 (g=0): err= 0:
193 write: io= 32MiB, bw= 666KiB/s, runt= 50320msec
194 slat (msec): min= 0, max= 136, avg= 0.03, dev= 1.92
195 clat (msec): min= 0, max= 631, avg=48.50, dev=86.82
196 bw (KiB/s) : min= 0, max= 1196, per=51.00%, avg=664.02, dev=681.68
197 cpu : usr=1.49%, sys=0.25%, ctx=7969
199 The client number is printed, along with the group id and error of that
200 thread. Below is the io statistics, here for writes. In the order listed,
203 io= Number of megabytes io performed
204 bw= Average bandwidth rate
205 runt= The runtime of that thread
206 slat= Submission latency (avg being the average, dev being the
207 standard deviation). This is the time it took to submit
208 the io. For sync io, the slat is really the completion
209 latency, since queue/complete is one operation there.
210 clat= Completion latency. Same names as slat, this denotes the
211 time from submission to completion of the io pieces. For
212 sync io, clat will usually be equal (or very close) to 0,
213 as the time from submit to complete is basically just
214 CPU time (io has already been done, see slat explanation).
215 bw= Bandwidth. Same names as the xlat stats, but also includes
216 an approximate percentage of total aggregate bandwidth
217 this thread received in this group. This last value is
218 only really useful if the threads in this group are on the
219 same disk, since they are then competing for disk access.
220 cpu= CPU usage. User and system time, along with the number
221 of context switches this thread went through.
223 After each client has been listed, the group statistics are printed. They
226 Run status group 0 (all jobs):
227 READ: io=64MiB, aggrb=22178, minb=11355, maxb=11814, mint=2840msec, maxt=2955msec
228 WRITE: io=64MiB, aggrb=1302, minb=666, maxb=669, mint=50093msec, maxt=50320msec
230 For each data direction, it prints:
232 io= Number of megabytes io performed.
233 aggrb= Aggregate bandwidth of threads in this group.
234 minb= The minimum average bandwidth a thread saw.
235 maxb= The maximum average bandwidth a thread saw.
236 mint= The minimum runtime of a thread.
237 maxt= The maximum runtime of a thread.
239 And finally, the disk statistics are printed. They will look like this:
241 Disk stats (read/write):
242 sda: ios=16398/16511, merge=30/162, ticks=6853/819634, in_queue=826487, util=100.00%
244 Each value is printed for both reads and writes, with reads first. The
247 ios= Number of ios performed by all groups.
248 merge= Number of merges io the io scheduler.
249 ticks= Number of ticks we kept the disk busy.
250 io_queue= Total time spent in the disk queue.
251 util= The disk utilization. A value of 100% means we kept the disk
252 busy constantly, 50% would be a disk idling half of the time.