fio2.1.10--HOWTO
1.0 Overview and history
------------------------
fio was originally written to save me the hassle of writing special test
case programs when I wanted to test a specific workload, either for
performance reasons or to find/reproduce a bug. The process of writing
such a test app can be tiresome, especially if you have to do it often.
Hence I needed a tool that would be able to simulate a given io workload
without resorting to writing a tailored test case again and again.
A test work load is difficult to define, though. There can be any number
of processes or threads involved, and they can each be using their own
way of generating io. You could have someone dirtying large amounts of
memory in an memory mapped file, or maybe several threads issuing
reads using asynchronous io. fio needed to be flexible enough to
simulate both of these cases, and many more.
2.0 How fio works
-----------------
The first step in getting fio to simulate a desired io workload, is
writing a job file describing that specific setup. A job file may contain
any number of threads and/or files - the typical contents of the job file
is a global section defining shared parameters, and one or more job
sections describing the jobs involved. When run, fio parses this file
and sets everything up as described. If we break down a job from top to
bottom, it contains the following basic parameters:
IO type Defines the io pattern issued to the
file(s).
We may only be reading
sequentially from this
file(s), or we may be
writing randomly. Or even
mixing reads and writes,
sequentially or randomly.
Block size In how large chunks are we issuing io? This
may be
a single value, or it
may describe a range of
block sizes.
IO size How much data are we going to be
reading/writing.
IO engine How do we issue io? We could be memory mapping
the
file, we could be using
regular read/write, we
could be using splice,
async io, syslet, or even
SG (SCSI generic
sg).
IO depth If the io engine is async, how large a
queuing
depth do we want to
maintain?
IO type Should we be doing buffered io, or
direct/raw io?
Num files How many files are we spreading the workload
over.
Num threads How many threads or processes should we
spread
this workload
over.
The above are the basic parameters defined for a workload, in addition
there's a multitude of parameters that modify other aspects of how this
job behaves.
3.0 Running fio
---------------使用命令行或者job file文件
See the README file for command line parameters, there are only a few
of them.
Running fio is normally the easiest part - you just give it the job file
(or job files) as parameters:
$ fio job_file
and it will start doing what the job_file tells it to do. You can give
more than one job file on the command line, fio will serialize the
running
of those files. Internally that is the same as using the 'stonewall'
parameter described the the parameter section.
If the job file contains only one job, you may as well just give the
parameters on the command line. The command line parameters are identical
to the job parameters, with a few extra that control global parameters
(see README). For example, for the job file parameter iodepth=2, the
mirror command line option would be --iodepth 2 or --iodepth=2. You can
also use the command line for giving more than one job entry. For each
--name option that fio sees, it will start a new job with that name.
Command line entries following a --name entry will apply to that job,
until there are no more entries or a new --name entry is seen. This is
similar to the job file options, where each option applies to the current
job until a new [] job entry is seen.
fio does not need to run as root, except if the files or devices
specified
in the job section requires that. Some other options may also be
restricted,
such as memory locking, io scheduler switching, and decreasing the nice
value.
4.0 Job file format
-------------------job file的格式怎么定义，可以参考example文件夹下的例子，其中有两个关于ssd的fio参考事例
As previously described, fio accepts one or more job files describing
what it is supposed to do. The job file format is the classic ini file,
where the names enclosed in [] brackets define the job name. You are free
to use any ascii name you want, except 'global' which has special
meaning.
A global section sets defaults for the jobs described in that file. A job
may override a global section parameter, and a job file may even have
several global sections if so desired. A job is only affected by a global
section residing above it. If the first character in a line is a ';' or a
'#', the entire line is discarded as a comment.
So let's look at a really simple job file that defines two processes, each
randomly reading from a 128MB file.
; -- start job file --
[global]
rw=randread
size=128m
[job1]
[job2]
; -- end job file --
As you can see, the job file sections themselves are empty as all the
described parameters are shared. As no filename= option is given, fio
makes up a filename for each of the jobs as it sees fit. On the command
line, this job would look as follows:
$ fio --name=global --rw=randread --size=128m --name=job1 --name=job2
Let's look at an example that has a number of processes writing randomly
to files.
; -- start job file --
[random-writers]
ioengine=libaio
iodepth=4
rw=randwrite
bs=32k
direct=0
size=64m
numjobs=4
; -- end job file --
Here we have no global section, as we only have one job defined anyway.
We want to use async io here, with a depth of 4 for each file. We also
increased the buffer size used to 32KB and define numjobs to 4 to
fork 4 identical jobs. The result is 4 processes each randomly writing
to their own 64MB file. Instead of using the above job file, you could
have given the parameters on the command line. For this case, you would
specify:
$ fio --name=random-writers --ioengine=libaio --iodepth=4 --rw=randwrite
--bs=32k --direct=0 --size=64m --numjobs=4
4.1 Environment variables
-------------------------还可以使用环境变量作为参数
fio also supports environment variable expansion in job files. Any
substring of the form "${VARNAME}" as part of an option value (in
other
words, on the right of the `='), will be expanded to the value of the
environment variable called VARNAME. If
no such environment variable
is defined, or VARNAME is the empty string, the empty string will be
substituted.
As an example, let's look at a sample fio invocation and job file:
$ SIZE=64m NUMJOBS=4 fio jobfile.fio
; -- start job file --
[random-writers]
rw=randwrite
size=${SIZE}
numjobs=${NUMJOBS}
; -- end job file --
This will expand to the following equivalent job file at runtime:
; -- start job file --
[random-writers]
rw=randwrite
size=64m
numjobs=4
; -- end job file --
fio ships with a few example job files, you can also look there for
inspiration.
4.2 Reserved keywords
---------------------保留的关键字
Additionally, fio has a set of reserved keywords that will be replaced
internally with the appropriate value. Those keywords are:
$pagesize The architecture page size of
the running system
$mb_memory Megabytes of total memory in
the system
$ncpus Number of online available
CPUs
These can be used on the command line or in the job file, and will be
automatically substituted with the current system values when the job
is run. Simple math is also supported on these keywords, so you can
perform actions like:
size=8*$mb_memory
and get that properly expanded to 8 times the size of memory in the
machine.
5.0 Detailed list of parameters
-------------------------------
This section describes in details each parameter associated with a job.
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.
time Integer with possible time
suffix. In seconds unless otherwise
specified, use eg 10m for 10
minutes. Accepts s/m/h for seconds,
minutes, and hours, and accepts 'ms'
(or 'msec') for milliseconds,
and 'us' (or 'usec') for
microseconds.
int SI integer. A whole number value,
which may contain a suffix
describing the base of the number.
Accepted suffixes are k/m/g/t/p,
meaning kilo, mega, giga, tera, and
peta. The suffix is not case
sensitive, and you may also include
trailing 'b' (eg 'kb' is the same
as 'k'). So if you want to specify
4096, you could either write
out '4096' or just give 4k. The
suffixes signify base 2 values, so
1024 is 1k and 1024k is 1m and so
on, unless the suffix is explicitly
set to a base 10 value using 'kib',
'mib', 'gib', etc. If that is the
case, then 1000 is used as the
multiplier. This can be handy for
disks, since manufacturers generally
use base 10 values when listing
the capacity of a drive. If the
option accepts an upper and lower
range, use a colon ':' or minus '-'
to separate such values. May also
include a prefix to indicate numbers
base. If 0x is used, the number
is assumed to be hexadecimal. See irange.
bool Boolean. Usually parsed as an
integer, however only defined for
true and false (1 and 0).
irange Integer range with suffix. Allows
value range to be given, such
as 1024-4096. A colon may also be
used as the separator, eg
1k:4k. If the option allows two sets
of ranges, they can be
specified with a ',' or '/'
delimiter: 1k-4k/8k-32k. Also see
int.
float_list A list of floating numbers,
separated by a ':' character.
With the above in mind, here follows the complete list of fio job
parameters.
name=str ASCII name of the job. This may
be used to override the
name printed by fio for this
job. Otherwise the job
name is used. On the command
line this parameter has the
special purpose of also
signaling the start of a new
job.
description=str Text description of
the job. Doesn't do anything except
dump this text description
when this job is run. It's
not parsed.
directory=str Prefix filenames with this
directory. Used to place files
in a different location than
"./". See the 'filename' option
for escaping certain
characters.
filename=str Fio normally makes up a
filename 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 filename for each of them to
override the default. If
the ioengine used is 'net',
the filename is the host, port,
and protocol to use in the
format of =host,port,protocol.
See ioengine=net for more. If
the ioengine is file based, you
can specify a number of files
by separating 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. On
Windows, disk devices are
accessed as \\.\PhysicalDrive0
for the first device,
\\.\PhysicalDrive1 for the
second etc. Note: Windows and
FreeBSD prevent write access
to areas of the disk containing
in-use data (e.g.
filesystems).
If the wanted filename does
need to include a colon, then
escape that with a '\'
character. For instance, if the filename
is
"/dev/dsk/foo@3,0:c", then you would use
filename="/dev/dsk/foo@3,0\:c".
'-' is a reserved name, meaning
stdin or stdout. Which of the
two depends on the read/write
direction set.
filename_format=str
If sharing multiple files
between jobs, it is usually necessary
to have fio generate the exact names that you
want. By default,
fio will name a file based on
the default file format
specification of
jobname.jobnumber.filenumber. With this
option, that can be
customized. Fio will recognize and replace
the following keywords in this
string:
$jobname
The name of the worker
thread or process.
$jobnum
The incremental number
of the worker thread or
process.
$filenum
The incremental number
of the file for that worker
thread or process.
To have dependent jobs share a
set of files, this option can
be set to have fio generate
filenames that are shared between
the two. For instance, if
testfiles.$filenum is specified,
file number 4 for any job will
be named testfiles.4. The
default of
$jobname.$jobnum.$filenum will be used if
no other format specifier is
given.
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
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:
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.
readwrite=str
rw=str Type of io pattern. Accepted
values are:
read Sequential reads
write Sequential writes
randwrite Random writes
randread Random reads
rw,readwrite Sequential mixed reads and writes
randrw Random mixed reads and writes
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. It is possible to specify
a number of IO's to do before
getting a new offset, this is
one by appending a
':<nr>' to the end of the string given.
For a random read, it would
look like 'rw=randread:8' for
passing in an offset modifier
with a value of 8. If the
suffix is used with a
sequential IO pattern, then the value
specified will be added to the
generated offset for each IO.
For instance, using
rw=write:4k will skip 4k for every
write. It turns sequential IO into
sequential IO with holes.
See the 'rw_sequencer'
option.
rw_sequencer=str If an offset modifier is given by appending a number to
the rw=<str> line, then
this option controls how that
number modifies the IO offset
being generated. Accepted
values are:
sequential Generate sequential offset
identical Generate the same offset
'sequential' 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. As sequential IO is
already sequential, setting
'sequential' for that would
not result in any differences.
'identical' behaves in a
similar fashion, except it sends
the same offset 8 number of
times before generating a new
offset.
kb_base=int 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.
unified_rw_reporting=bool Fio normally
reports statistics on a per
data direction basis, meaning
that read, write, and trim are
accounted and reported
separately. If this option is set,
the fio will sum the results
and report them as "mixed"
instead.
randrepeat=bool For random IO
workloads, seed the generator in a predictable
way so that results are
repeatable across repetitions.
randseed=int Seed the random number
generators based on this seed value, to
be able to control what
sequence of output is being generated.
If not set, the random
sequence depends on the randrepeat
setting.
use_os_rand=bool Fio can either use the random generator supplied by the
OS
to generator random offsets,
or it can use it's own internal
generator (based on
Tausworthe). Default is to use the
internal generator, which is
often of better quality and
faster.
fallocate=str Whether pre-allocation is
performed when laying down files.
Accepted values are:
none Do not pre-allocate space
posix Pre-allocate via
posix_fallocate()
keep Pre-allocate via fallocate()
with
FALLOC_FL_KEEP_SIZE
set
0 Backward-compatible alias for 'none'
1 Backward-compatible alias for 'posix'
May not be available on all
supported platforms. 'keep' is only
available on Linux.If using
ZFS on Solaris this must be set to
'none' because ZFS doesn't
support it. Default: 'posix'.
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=int 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 nrfiles and
filesize options are given,
fio will divide this size
between the available files
specified by the job. If not
set, fio will use the full
size of the given files or
devices. If the the files
do not exist, size must be
given. It is also possible to
give size as a percentage
between 1 and 100. If size=20%
is given, fio will use 20% of
the full size of the given
files or devices.
io_limit=int Normally fio operates
within the region set by 'size', which
means that the 'size' option
sets both the region and size of
IO to be performed. Sometimes
that is not what you want. With
this option, it is possible to
define just the amount of IO
that fio should do. For
instance, if 'size' is set to 20G and
'io_limit'
is set to 5G, fio will perform IO within the first
20G but exit when 5G have been
done.
filesize=int 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.
file_append=bool Perform IO after the end
of the file. Normally fio will
operate within the size of a
file. If this option is set, then
fio will append to the file instead.
This has identical
behavior to setting offset to
the size of a file. This option
is ignored on non-regular
files.
fill_device=bool
fill_fs=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.
For a read workload, the mount
point will be filled first
then IO started on the result. This
option doesn't make sense if
operating on a raw device node,
since the size of that is
already known by the file system.
Additionally, writing beyond
end-of-device will not return
ENOSPC there.
blocksize=int
bs=int The block size used for the
io units. Defaults to 4k. Values
can be given for both read and
writes. If a single int is
given, it will apply to both.
If a second int is specified
after a comma, it will apply
to writes only. In other words,
the format is either
bs=read_and_write or bs=read,write,trim.
bs=4k,8k will thus use 4k
blocks for reads, 8k blocks for
writes, and 8k for trims. You
can terminate the list with
a trailing comma. bs=4k,8k,
would use the default value for
trims.. If you only wish to
set the write size, you
can do so by passing an empty
read size - bs=,8k will set
8k for writes and leave the
read default value.
blockalign=int
ba=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.
blocksize_range=irange
bsrange=irange Instead of giving a
single block size, specify a range
and fio will mix the issued io
block sizes. The issued
io unit will always be a
multiple of the minimum value
given (also see bs_unaligned).
Applies to both reads and
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.
bssplit also supports giving
separate splits to reads and
writes. The format is
identical to what bs= accepts. You
have to separate the read and
write parts with a comma. So
if you want a workload that
has 50% 2k reads and 50% 4k reads,
while having 90% 4k writes and
10% 8k writes, you would
specify:
bssplit=2k/50:4k/50,4k/90,8k/10
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.
bs_is_seq_rand If this option is set,
fio will use the normal read,write
blocksize settings as
sequential,random instead. Any random
read or write will use the
WRITE blocksize settings, and any
sequential read or write will
use the READ blocksize setting.
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.
The resulting IO buffers will
not be completely zeroed,
unless scramble_buffers is
also turned off.
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.
scramble_buffers=bool If
refill_buffers is too costly and the target is
using data deduplication, then
setting this option will
slightly modify the IO buffer
contents to defeat normal
de-dupe attempts. This is not
enough to defeat more clever
block compression attempts,
but it will stop naive dedupe of
blocks. Default: true.
buffer_compress_percentage=int If this is
set, then fio will attempt to
provide IO buffer content (on
WRITEs) that compress to
the specified level. Fio does
this by providing a mix of
random data and zeroes. Note
that this is per block size
unit, for file/disk wide
compression level that matches
this setting, you'll also want
to set refill_buffers.
buffer_compress_chunk=int See
buffer_compress_percentage. This
setting allows fio to manage
how big the ranges of random
data and zeroed data is.
Without this set, fio will
provide buffer_compress_percentage
of blocksize random
data, followed by the
remaining zeroed. With this set
to some chunk size smaller
than the block size, fio can
alternate random and zeroed
data throughout the IO
buffer.
buffer_pattern=str If set, fio will fill
the io buffers with this pattern.
If not set, the contents of io
buffers is defined by the other
options related to buffer
contents. The setting can be any
pattern of bytes, and can be
prefixed with 0x for hex values.
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
the same as nrfiles, can be
set smaller to limit the number
simultaneous opens.
file_service_type=str Defines how fio
decides which file from a job to
service next. The following
types are defined:
random Just choose a file at random.
roundrobin Round robin over open files. This
is the
default.
sequential Finish one file before moving on to
the next. Multiple
files can still be
open depending on
'openfiles'.
The string can have a number
appended, indicating how
often to switch to a new file.
So if option random:4 is
given, fio will switch to a
new random file after 4 ios
have been issued.
ioengine=str Defines how the job issues
io to the file. The following
types are defined:
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.
psyncv Basic preadv(2) or pwritev(2) IO.
libaio Linux native asynchronous io. Note that
Linux
may only support
queued behaviour with
non-buffered IO
(set direct=1 or buffered=0).
This engine defines
engine specific options.
posixaio glibc posix
asynchronous io.
solarisaio Solaris
native asynchronous io.
windowsaio Windows
native asynchronous io.
mmap File is memory mapped and data copied
to/from using
memcpy(3).
splice splice(2) is used to transfer the data
and
vmsplice(2) to
transfer data from user
space to the
kernel.
syslet-rw Use the syslet
system calls to make
regular read/write
async.
sg SCSI generic sg v3 io. May either be
synchronous using
the SG_IO ioctl, or if
the target is an sg
character device
we use read(2) and write(2) for asynchronous
io.
null Doesn't transfer any data, just
pretends
to. This is mainly
used to exercise fio
itself and for
debugging/testing purposes.
net Transfer over the network to given
host:port.
Depending on the
protocol used, the hostname,
port, listen and
filename options are used to
specify what sort
of connection to make, while
the protocol option
determines which protocol
will be used.
This engine defines
engine specific options.
netsplice Like net, but
uses splice/vmsplice to
map data and
send/receive.
This engine defines
engine specific options.
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. In
case of SMP machines,
use
numjobs=<no_of_cpu> 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.
rdma The RDMA I/O engine supports
both RDMA
memory semantics
(RDMA_WRITE/RDMA_READ) and
channel semantics
(Send/Recv) for the
InfiniBand, RoCE
and iWARP protocols.
falloc IO engine that does regular fallocate
to
simulate data transfer as fio ioengine.
DDIR_READ
does fallocate(,mode = keep_size,)
DDIR_WRITE does fallocate(,mode = 0)
DDIR_TRIM
does fallocate(,mode = punch_hole)
e4defrag IO engine that
does regular EXT4_IOC_MOVE_EXT
ioctls to simulate defragment activity
in
request to DDIR_WRITE event
external Prefix to
specify loading an external
IO engine object
file. Append the engine
filename, eg
ioengine=external:/tmp/foo.o
to load ioengine
foo.o in /tmp.
iodepth=int This defines how many io
units to keep in flight against
the file. The default is 1 for
each file defined in this
job, can be overridden with a
larger value for higher
concurrency. Note that
increasing iodepth beyond 1 will not
affect synchronous ioengines
(except for small degress when
verify_async is in use). Even
async engines may impose OS
restrictions causing the
desired depth not to be achieved.
This may happen on Linux when
using libaio and not setting
direct=1, since buffered IO is
not async on that OS. Keep an
eye on the IO depth
distribution in the fio output to verify
that the achieved depth is as
expected. Default: 1.
iodepth_batch_submit=int
iodepth_batch=int This defines how many pieces of IO to submit at once.
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_batch_complete=int 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
iodepth_low. 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.
iodepth_low=int The low water mark
indicating when to start filling
the queue again. Defaults to
the same as iodepth, meaning
that fio will attempt to keep
the queue full at all times.
If iodepth is set to eg 16 and
iodepth_low is set to 4, then
after fio has filled the queue
of 16 requests, it will let
the depth drain down to 4
before starting to fill it again.
direct=bool If value is true, use
non-buffered io. This is usually
O_DIRECT. Note that ZFS on
Solaris doesn't support direct io.
On Windows the synchronous
ioengines don't support direct io.
atomic=bool If value is true, attempt
to use atomic direct IO. Atomic
writes are guaranteed to be
stable once acknowledged by
the operating system. Only
Linux supports O_ATOMIC right
now.
buffered=bool If value is true, use
buffered io. This is the opposite
of the 'direct' option.
Defaults to true.
offset=int Start io at the given offset
in the file. The data before
the given offset will not be
touched. This effectively
caps the file size at
real_size - offset.
offset_increment=int If this is
provided, then the real offset becomes
the offset + offset_increment
* thread_number, where the
thread number is a counter
that starts at 0 and is incremented
for each job. This option is
useful if there are several jobs
which are intended to operate
on a file in parallel in disjoint
segments, with even spacing
between the starting points.
number_ios=int Fio will normally
perform IOs until it has exhausted the size
of the region set by size=, or
if it exhaust the allocated
time (or hits an error
condition). With this setting, the
range/size can be set
independently of the number of IOs to
perform. When fio reaches this
number, it will exit normally
and report status.
fsync=int If writing to a file, issue a
sync of the dirty data
for every number of blocks
given. For example, if you give
32 as a parameter, fio will
sync the file for every 32
writes issued. If fio is using
non-buffered io, we may
not sync the file. The
exception is the sg io engine, which
synchronizes the disk cache
anyway.
fdatasync=int Like fsync= but uses
fdatasync() to only sync data and not
metadata blocks.
In FreeBSD and Windows there
is no fdatasync(), this falls back to
using fsync()
sync_file_range=str:val Use
sync_file_range() for every 'val' number of
write operations. Fio will
track range of writes that
have happened since the last
sync_file_range() call. 'str'
can currently be one or more
of:
wait_before SYNC_FILE_RANGE_WAIT_BEFORE
write SYNC_FILE_RANGE_WRITE
wait_after SYNC_FILE_RANGE_WAIT_AFTER
So if you do
sync_file_range=wait_before,write:8, fio would
use
SYNC_FILE_RANGE_WAIT_BEFORE | SYNC_FILE_RANGE_WRITE for
every 8 writes. Also see the
sync_file_range(2) man page.
This option is Linux
specific.
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 a write stage has completed.
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.
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
rwmixread and rwmixwrite is
given and the values do not add
up to 100%, the latter of the
two will be used to override
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.
random_distribution=str:float By default,
fio will use a completely uniform
random distribution when asked
to perform random IO. Sometimes
it is useful to skew the
distribution in specific ways,
ensuring that some parts of
the data is more hot than others.
fio includes the following
distribution models:
random Uniform random distribution
zipf Zipf distribution
pareto Pareto distribution
When using a zipf or pareto
distribution, an input value
is also needed to define the
access pattern. For zipf, this
is the zipf theta. For pareto,
it's the pareto power. Fio
includes a test program,
genzipf, that can be used visualize
what the given input values
will yield in terms of hit rates.
If you wanted to use zipf with
a theta of 1.2, you would use
random_distribution=zipf:1.2
as the option. If a non-uniform
model is used, fio will
disable use of the random map.
percentage_random=int For a random
workload, set how big a percentage should
be random. This defaults to
100%, in which case the workload
is fully random. It can be set
from anywhere from 0 to 100.
Setting it to 0 would make the
workload fully sequential. Any
setting in between will result
in a random mix of sequential
and random IO, at the given
percentages. It is possible to
set different values for
reads, writes, and trim. To do so,
simply use a comma separated
list. See blocksize.
norandommap Normally fio will cover every
block of the file when doing
random IO. If this option is
given, fio will just get a
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= if and only if multiple
blocksizes (via bsrange=) are
used, since fio only tracks
complete rewrites of
blocks.
softrandommap=bool 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.
random_generator=str Fio supports the
following engines for generating
IO offsets for random
IO:
tausworthe Strong 2^88 cycle random number generator
lfsr Linear feedback shift register generator
Tausworthe is a strong random
number generator, but it
requires tracking on the side
if we want to ensure that
blocks are only read or
written once. LFSR guarantees
that we never generate the
same offset twice, and it's
also less computationally
expensive. It's not a true
random generator, however,
though for IO purposes it's
typically good enough. LFSR
only works with single
block sizes, not with
workloads that use multiple block
sizes. If used with such a
workload, fio may read or write
some blocks multiple
times.
nice=int Run the job with the given
nice value. See man nice(2).
prio=int Set the io priority value of
this job. Linux limits us to
a positive value between 0 and
7, with 0 being the highest.
See man ionice(1).
prioclass=int Set the io priority
class. See man ionice(1).
thinktime=int Stall the job x
microseconds after an io has completed before
issuing the next. May be used
to simulate processing being
done by an application. See
thinktime_blocks and
thinktime_spin.
thinktime_spin=int
Only valid if thinktime is set
- pretend to spend CPU time
doing something with the data
received, before falling back
to sleeping for the rest of
the period specified by
thinktime.
thinktime_blocks=int
Only valid if thinktime is set
- control how many blocks
to issue, before waiting
'thinktime' usecs. If not set,
defaults to 1 which will make
fio wait 'thinktime' usecs
after every block. This
effectively makes any queue depth
setting redundant, since no
more than 1 IO will be queued
before we have to complete it
and do our thinktime. In
other words, this setting
effectively caps the queue depth
if the latter is larger.
rate=int Cap the bandwidth used by
this job. The number is in bytes/sec,
the normal suffix rules apply.
You can use rate=500k to limit
reads and writes to 500k each,
or you can specify read and
writes separately. Using
rate=1m,500k would limit reads to
1MB/sec and writes to
500KB/sec. Capping only reads or
writes can be done with
rate=,500k or rate=500k,. The former
will only limit writes (to
500KB/sec), the latter will only
limit reads.
ratemin=int Tell fio to do whatever
it can to maintain at least this
bandwidth. Failing to meet
this requirement, will cause
the job to exit. The same
format as rate is used for
read vs write
separation.
rate_iops=int Cap the bandwidth to this
number of IOPS. Basically the same
as rate, just specified
independently of bandwidth. If the
job is given a block size range
instead of a fixed value,
the smallest block size is
used as the metric. The same format
as rate is used for read vs
write separation.
rate_iops_min=int If fio doesn't meet this rate of IO, it will cause
the job to exit. The same
format as rate is used for read vs
write separation.
latency_target=int If set, fio will
attempt to find the max performance
point that the given workload
will run at while maintaining a
latency below this target. The
values is given in microseconds.
See latency_window and
latency_percentile
latency_window=int Used with
latency_target to specify the sample window
that the job is run at varying
queue depths to test the
performance. The value is
given in microseconds.
latency_percentile=float The percentage
of IOs that must fall within the
criteria specified by
latency_target and latency_window. If not
set, this defaults to 100.0,
meaning that all IOs must be equal
or below to the value set by
latency_target.
max_latency=int If set, fio will exit
the job if it exceeds this maximum
latency. It will exit with an
ETIME error.
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. 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. This option doesn't
work well for a higher CPU
count than what you can store in
an integer mask, so it can
only control cpus 1-32. For
boxes with larger CPU counts,
use cpus_allowed.
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. This options also
allows a range of CPUs. Say
you wanted a binding to CPUs
1, 5, and 8-15, you would set
cpus_allowed=1,5,8-15.
cpus_allowed_policy=str Set the policy of how fio distributes the CPUs
specified by cpus_allowed or
cpumask. Two policies are
supported:
shared All jobs will share the CPU set specified.
split Each job will get a unique CPU from the CPU set.
'shared' is the default
behaviour, if the option isn't
specified. If split is
specified, then fio will will assign
one cpu per job. If not enough
CPUs are given for the jobs
listed, then fio will
roundrobin the CPUs in the set.
numa_cpu_nodes=str Set this job running on spcified NUMA nodes' CPUs. The
arguments allow comma
delimited list of cpu numbers,
A-B ranges, or 'all'. Note, to
enable numa options support,
fio must be built on a system
with libnuma-dev(el) installed.
numa_mem_policy=str Set this job's memory policy and corresponding NUMA
nodes. Format of the
argements:
<mode>[:<nodelist>]
`mode' is one of the following
memory policy:
default, prefer, bind,
interleave, local
For `default' and `local'
memory policy, no node is
needed to be specified.
For `prefer', only one node is
allowed.
For `bind' and `interleave',
it allow comma delimited
list of numbers, A-B ranges,
or 'all'.
startdelay=time Start this job the
specified number of seconds after fio
has started. Only useful if
the job file contains several
jobs, and you want to delay
starting some jobs to a certain
time.
runtime=time Tell fio to terminate
processing after the specified number
of seconds. It can be quite
hard to determine for how long
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 completely read or
written. It will simply loop
over the same workload
as many times as the runtime
allows.
ramp_time=time 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 ramp_time is
considered lead in time for a job,
thus it will increase the
total runtime if a special timeout
or runtime is specified.
invalidate=bool Invalidate the
buffer/page cache parts for this file prior
to starting io. Defaults to
true.
sync=bool Use sync io for buffered writes.
For the majority of the
io engines, this means using
O_SYNC.
iomem=str
mem=str Fio can use various types
of memory as the io unit buffer.
The allowed values are:
malloc Use memory from malloc(3) as the buffers.
shm Use shared memory as the buffers.
Allocated
through
shmget(2).
shmhuge Same as shm, but use huge pages as
backing.
mmap Use mmap to allocate buffers. May either
be
anonymous memory,
or can be file backed if
a filename is given
after the option. The
format is
mem=mmap:/path/to/file.
mmaphuge Use a memory
mapped huge file as the buffer
backing. Append
filename after mmaphuge, ala
mem=mmaphuge:/hugetlbfs/file
The area allocated is a
function of the maximum allowed
bs size for the job,
multiplied by the io depth given. Note
that for shmhuge and mmaphuge
to work, the system must have
free huge pages allocated.
This can normally be checked
and set by reading/writing /proc/sys/vm/nr_hugepages
on a
Linux system. Fio assumes a
huge page is 4MB in size. So
to calculate the number of
huge pages you need for a given
job file, add up the io depth
of all jobs (normally one unless
iodepth= is used) and multiply
by the maximum bs set. Then
divide that number by the huge
page size. You can see the
size of the huge pages in
/proc/meminfo. If no huge pages
are allocated by having a
non-zero number in nr_hugepages,
using mmaphuge or shmhuge will
fail. Also see hugepage-size.
mmaphuge also needs to have
hugetlbfs mounted and the file
location should point there.
So if it's mounted in /huge,
you would use
mem=mmaphuge:/huge/somefile.
iomem_align=int 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 iodepth the
alignment of the following buffers
are given by the bs used. In
other words, if using a bs that is
a multiple of the page sized
in the system, all buffers will
be aligned to this value. If
using a bs that is not page
aligned, the alignment of
subsequent IO memory buffers is the
sum of the iomem_align and bs
used.
hugepage-size=int
Defines the size of a huge
page. Must at least be equal
to the system setting, see
/proc/meminfo. Defaults to 4MB.
Should probably always be a
multiple of megabytes, so using
hugepage-size=Xm is the
preferred way to set this to avoid
setting a non-pow-2 bad
value.
exitall When one job finishes,
terminate the rest. The default is
to wait for each job to
finish, sometimes that is not the
desired action.
bwavgtime=int Average the calculated
bandwidth over the given time. Value
is specified in
milliseconds.
iopsavgtime=int Average the calculated
IOPS over the given time. Value
is specified in
milliseconds.
create_serialize=bool If true, serialize
the file creating for the jobs.
This may be handy to
avoid interleaving of data
files, which may greatly
depend on the filesystem
used and even the number
of processors in the system.
create_fsync=bool fsync the data file
after creation. This is the
default.
create_on_open=bool Don't pre-setup the
files for IO, just create open()
when it's time to do IO
to that file.
create_only=bool If true, fio will only
run the setup phase of the job.
If files need to be laid
out or updated on disk, only
that will be done. The
actual job contents are not
executed.
pre_read=bool If this is given, files will
be pre-read into memory before
starting the given IO
operation. This will also clear
the 'invalidate' 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.
unlink=bool Unlink the job files when
done. Not the default, as repeated
runs of that job would then
waste time recreating the file
set again and again.
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.
verify_only Do not perform specified
workload---only verify data still
matches previous invocation of
this workload. This option
allows one to check data
multiple times at a later date
without overwriting it. This
option makes sense only for
workloads that write data, and
does not support workloads
with the time_based option
set.
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.
crc32c Use a crc32c sum of the data area and
store
it in the header of
each block.
crc32c-intel Use
hardware assisted crc32c calcuation
provided on SSE4.2
enabled processors. Falls
back to regular
software crc32c, if not
supported by the
system.
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.
xxhash Use xxhash as the checksum function.
Generally
the fastest
software checksum that fio
supports.
sha512 Use sha512 as the checksum function.
sha256 Use sha256 as the checksum function.
sha1 Use optimized sha1 as the checksum
function.
meta Write extra information about each io
(timestamp, block
number etc.). The block
number is verified.
The io sequence number is
verified for workloads that write data.
See also
verify_pattern.
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. 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.
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=int Swap the verification
header with data somewhere else
in the block before
writing. Its swapped back before
verifying.
verify_interval=int 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=str 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(it can be
either a decimal or a hex number).
The verify_pattern if larger
than a 32-bit quantity has to
be a hex number that starts
with either "0x" or "0X". Use
with verify=meta.
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.
verify_dump=bool If set, dump the
contents of both the original data
block and the data block we
read off disk to files. This
allows later analysis to
inspect just what kind of data
corruption occurred. Off by
default.
verify_async=int 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
iodepth setting higher than 1,
as it allows them to have
IO in flight while verifies
are running.
verify_async_cpus=str Tell fio to set
the given CPU affinity on the
async IO verification threads.
See cpus_allowed for the
format used.
verify_backlog=int Fio will normally
verify the written contents of a
job that utilizes verify once
that job has completed. In
other words, everything is
written then everything is read
back and verified. You may
want to verify continually
instead for a variety of
reasons. Fio stores the meta data
associated with an IO block in
memory, so for large
verify workloads, quite a bit
of memory would be used up
holding this meta data. If
this option is enabled, fio
will write only N blocks
before verifying these blocks.
verify_backlog_batch=int Control how many
blocks fio will verify
if verify_backlog is set. If
not set, will default to
the value of verify_backlog
(meaning the entire queue
is read back and
verified). If verify_backlog_batch
is
less than verify_backlog then
not all blocks will be verified,
if verify_backlog_batch is
larger than verify_backlog, some
blocks will be verified more
than once.
stonewall
wait_for_previous Wait for preceding jobs in the job file to exit, before
starting this one. Can be used
to insert serialization
points in the job file. A
stone wall also implies starting
a new reporting group.
new_group Start a new reporting
group. See: group_reporting.
numjobs=int Create the specified number
of clones of this job. May be
used to setup a larger number
of threads/processes doing
the same thing. Each thread is
reported separately; to see
statistics for all clones as a
whole, use group_reporting in
conjunction with
new_group.
group_reporting It may sometimes be
interesting to display statistics for
groups of jobs as a whole
instead of for each individual job.
This is especially true if
'numjobs' is used; looking at
individual thread/process
output quickly becomes unwieldy.
To see the final report
per-group instead of per-job, use
'group_reporting'. Jobs in a
file will be part of the same
reporting group, unless if
separated by a stonewall, or by
using 'new_group'.
thread fio defaults to forking
jobs, however if this option is
given, fio will use
pthread_create(3) to create threads
instead.
zonesize=int Divide a file into zones
of the specified size. See zoneskip.
zoneskip=int Skip the specified number
of bytes when zonesize data has
been read. The two zone
options can be used to only do
io on zones of a file.
write_iolog=str Write the issued io
patterns to the specified file. See
read_iolog. Specify a separate file for each job,
otherwise
the iologs will be
interspersed and the file may be corrupt.
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. 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 (blkparse
<device> -o /dev/null -d file_for_fio.bin).
replay_no_stall=int When replaying I/O with read_iolog the default
behavior
is to attempt to respect the
time stamps within the log and
replay them with the
appropriate delay between IOPS. By
setting this variable fio will
not respect the timestamps and
attempt to replay them as fast
as possible while still
respecting ordering. The result is the same I/O pattern to a
given device, but different
timings.
replay_redirect=str While replaying I/O patterns using read_iolog the
default behavior is to replay
the IOPS onto the major/minor
device that each IOP was
recorded from. This is sometimes
undesirable because on a
different machine those major/minor
numbers can map to a different
device. Changing hardware on
the same system can also
result in a different major/minor
mapping. Replay_redirect causes all IOPS to be
replayed onto
the single specified device
regardless of the device it was
recorded from. i.e.
replay_redirect=/dev/sdc would cause all
IO in the blktrace to be
replayed onto /dev/sdc. This means
multiple devices will be
replayed onto a single, if the trace
contains multiple
devices. If you want multiple devices to
be
replayed concurrently to
multiple redirected devices you must
blkparse your trace into
separate traces and replay them with
independent fio invocations. Unfortuantely this also breaks
the strict time ordering
between multiple device accesses.
write_bw_log=str 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 write_lat_log for
behaviour of given
filename. For this option, the
suffix is _bw.log.
write_lat_log=str Same as write_bw_log, except that this option stores io
submission, completion, and
total latencies instead. 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. So if one specifies
write_lat_log=foo
The actual log names will be
foo_slat.log, foo_clat.log,
and foo_lat.log. This helps
fio_generate_plot fine the logs
automatically.
write_iops_log=str Same as write_bw_log, but writes IOPS. 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.
log_avg_msec=int By default, fio will log an entry in the iops, latency,
or bw log for every IO that
completes. When writing to the
disk log, that can quickly
grow to a very large size. Setting
this option makes fio average
the each log entry over the
specified period of time,
reducing the resolution of the log.
Defaults to 0.
lockmem=int Pin down the specified
amount of memory with mlock(2). Can
potentially be used instead of
removing memory or booting
with less memory to simulate a
smaller amount of memory.
The amount specified is per
worker.
exec_prerun=str Before running this
job, issue the command specified
through system(3). Output is
redirected in a file called
jobname.prerun.txt.
exec_postrun=str After the job completes, issue the command specified
though system(3). Output is redirected in a
file called
jobname.postrun.txt.
ioscheduler=str Attempt to switch the
device hosting the file to the specified
io scheduler before
running.
disk_util=bool Generate disk utilization
statistics, if the platform
supports it. Defaults to
on.
disable_lat=bool Disable measurements of total 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.
disable_clat=bool Disable measurements of completion latency numbers. See
disable_lat.
disable_slat=bool Disable measurements of submission latency numbers. See
disable_slat.
disable_bw=bool Disable measurements of
throughput/bandwidth numbers. See
disable_lat.
clat_percentiles=bool Enable the reporting of percentiles of
completion latencies.
percentile_list=float_list Overwrite the default list of percentiles
for completion latencies. Each
number is a floating
number in the range (0,100],
and the maximum length of
the list is 20. Use ':' to
separate the numbers, and
list the numbers in ascending
order. For example,
--percentile_list=99.5:99.9
will cause fio to report
the values of completion
latency below which 99.5% and
99.9% of the observed
latencies fell, respectively.
clocksource=str Use the given
clocksource as the base of timing. The
supported options are:
gettimeofday gettimeofday(2)
clock_gettime clock_gettime(2)
cpu Internal CPU clock source
cpu is the preferred
clocksource if it is reliable, as it
is very fast (and fio is heavy
on time calls). Fio will
automatically use this
clocksource if it's supported and
considered reliable on the
system it is running on, unless
another clocksource is
specifically set. For x86/x86-64 CPUs,
this means supporting TSC
Invariant.
gtod_reduce=bool 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.
gtod_cpu=int 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.
continue_on_error=str Normally fio
will exit the job on the first observed
failure. If this option is
set, fio will continue the job when
there is a 'non-fatal error'
(EIO or EILSEQ) until the runtime
is exceeded or the I/O size
specified is completed. If this
option is used, there are two
more stats that are appended,
the total error count and the
first error. The error field
given in the stats is the
first error that was hit during the
run.
The allowed values are:
none Exit on any IO or verify errors.
read Continue on read errors, exit on all
others.
write Continue on write errors, exit on all
others.
io Continue on any IO error, exit on all
others.
verify Continue on verify errors, exit on all
others.
all Continue on all errors.
0 Backward-compatible alias for 'none'.
1 Backward-compatible alias for 'all'.
ignore_error=str Sometimes you want to ignore some errors during test
in that case you can specify error list for
each error type.
ignore_error=READ_ERR_LIST,WRITE_ERR_LIST,VERIFY_ERR_LIST
errors for given error type is separated with
':'. Error
may be symbol ('ENOSPC', 'ENOMEM') or
integer.
Example:
ignore_error=EAGAIN,ENOSPC:122
This option will ignore EAGAIN from READ, and ENOSPC
and
122(EDQUOT) from WRITE.
error_dump=bool If set dump every error even if it is non fatal, true
by default. If disabled only
fatal error will be dumped
cgroup=str 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
cgroup_weight=int 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.
cgroup_nodelete=bool Normally fio will delete the cgroups it has created
after
the job completion. To
override this behavior and to leave
cgroups around after the job
completion, set cgroup_nodelete=1.
This can be useful if one
wants to inspect various cgroup
files after job completion.
Default: false
uid=int Instead of running as the
invoking user, set the user ID to
this value before the
thread/process does any work.
gid=int Set group ID, see uid.
flow_id=int The ID of the flow. If not
specified, it defaults to being a
global flow. See flow.
flow=int Weight in token-based flow
control. If this value is used, then
there is a 'flow counter'
which is used to regulate the
proportion of activity between
two or more jobs. fio attempts
to keep this flow counter near
zero. The 'flow' parameter
stands for how much should be
added or subtracted to the flow
counter on each iteration of
the main I/O loop. That is, if
one job has flow=8 and another
job has flow=-1, then there
will be a roughly 1:8 ratio in
how much one runs vs the other.
flow_watermark=int The maximum value
that the absolute value of the flow
counter is allowed to reach
before the job must wait for a
lower value of the
counter.
flow_sleep=int The period of time, in
microseconds, to wait after the flow
watermark has been exceeded
before retrying operations
In addition, there are some parameters which are only valid when a
specific
ioengine is in use. These are used identically to normal parameters, with
the
caveat that when used on the command line, they must come after the
ioengine
that defines them is selected.
[libaio] userspace_reap Normally, with the libaio engine in use, fio will
use
the io_getevents system call
to reap newly returned events.
With this flag turned on, the
AIO ring will be read directly
from user-space to reap
events. The reaping mode is only
enabled when polling for a
minimum of 0 events (eg when
iodepth_batch_complete=0).
[cpu] cpuload=int Attempt to use the specified percentage of CPU cycles.
[cpu] cpuchunks=int Split the load into cycles of the given time. In
microseconds.
[cpu] exit_on_io_done=bool Detect when IO threads are done, then exit.
[netsplice] hostname=str
[net] hostname=str The host name or IP address to use for TCP or UDP based
IO.
If the job is a TCP listener
or UDP reader, the hostname is not
used and must be omitted
unless it is a valid UDP multicast
address.
[netsplice] port=int
[net] port=int The TCP or UDP port to
bind to or connect to.
[netsplice] interface=str
[net] interface=str The IP address of
the network interface used to send or
receive UDP multicast
[netsplice] ttl=int
[net] ttl=int Time-to-live value for
outgoing UDP multicast packets.
Default: 1
[netsplice] nodelay=bool
[net] nodelay=bool Set TCP_NODELAY on
TCP connections.
[netsplice] protocol=str
[netsplice] proto=str
[net] protocol=str
[net] proto=str The network protocol to
use. Accepted values are:
tcp Transmission control protocol
tcpv6 Transmission control protocol V6
udp User datagram protocol
udpv6 User datagram protocol V6
unix UNIX domain socket
When the protocol is TCP or
UDP, the port must also be given,
as well as the hostname if the
job is a TCP listener or UDP
reader. For unix sockets, the
normal filename option should be
used and the port is
invalid.
[net] listen For TCP network connections,
tell fio to listen for incoming
connections rather than
initiating an outgoing connection. The
hostname must be omitted if
this option is used.
[net] pingpong Normaly a network
writer will just continue writing data, and
a network reader will just
consume packages. If pingpong=1
is set, a writer will send its
normal payload to the reader,
then wait for the reader to
send the same payload back. This
allows fio to measure network
latencies. The submission
and completion latencies then
measure local time spent
sending or receiving, and the
completion latency measures
how long it took for the other
end to receive and send back.
For UDP multicast traffic
pingpong=1 should only be set for a
single reader when multiple
readers are listening to the same
address.
[e4defrag] donorname=str
File will be used as a block donor(swap
extents between files)
[e4defrag] inplace=int
Configure donor file blocks
allocation strategy
0(default): Preallocate
donor's file on init
1 : allocate space immidietly
inside defragment event,
and free right after event
6.0 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: 1: [_r] [24.8% done] [ 13509/
8334 kb/s] [eta 00h:01m:31s]
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.
I Thread initialized, waiting or
generating necessary data.
p Thread
running pre-reading file(s).
R Running,
doing sequential reads.
r Running,
doing random reads.
W Running,
doing sequential writes.
w Running,
doing random writes.
M Running,
doing mixed sequential reads/writes.
m Running,
doing mixed random reads/writes.
F Running,
currently waiting for fsync()
f Running,
finishing up (writing IO logs, etc)
V Running,
doing verification of written data.
E Thread exited, not reaped by
main thread yet.
_ Thread reaped, or
X Thread reaped, exited with an
error.
K Thread reaped, exited due to
signal.
The other values are fairly self explanatory - number of threads
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). Note that the string is displayed in
order,
so it's possible to tell which of the jobs are currently doing what. The
first character is the first job defined in the job file, and so forth.
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= 32MB, bw=
666KB/s, iops=89 , runt= 50320msec
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 (KB/s) : min= 0, max= 1196, per=51.00%, avg=664.02, stdev=681.68
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%
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
iops= Average IOs performed per
second
runt= The runtime of that
thread
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. This
value can be in milliseconds
or microseconds, fio will choose
the most appropriate base and
print that. In the example
above, milliseconds is the
best scale. Note: in --minimal mode
latencies are always expressed
in microseconds.
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, 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,
meaning that 2=1.6% means that
1.6% of the IO completed
within 2 msecs, 20=12.8% means
that 12.8% of the IO
took more than 10 msecs, but
less than (or equal to) 20 msecs.
After each client has been listed, the group statistics are printed. They
will look like this:
Run status group 0 (all jobs):
READ: io=64MB, aggrb=22178,
minb=11355, maxb=11814, mint=2840msec, maxt=2955msec
WRITE: io=64MB, 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 smallest runtime of the
threads in that group.
maxt= The longest runtime of the
threads in that group.
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.
It is also possible to get fio to dump the current output while it is
running, without terminating the job. To do that, send fio the USR1
signal.
You can also get regularly timed dumps by using the --status-interval
parameter, or by creating a file in /tmp named fio-dump-status. If fio
sees this file, it will unlink it and dump the current output status.
7.0 Terse output
----------------
For scripted usage where you typically want to generate tables or graphs
of the results, fio can output the results in a semicolon separated
format.
The format is one long line of values, such as:
2;card0;0;0;7139336;121836;60004;1;10109;27.932460;116.933948;220;126861;3495.446807;1085.368601;226;126864;3523.635629;1089.012448;24063;99944;50.275485%;59818.274627;5540.657370;7155060;122104;60004;1;8338;29.086342;117.839068;388;128077;5032.488518;1234.785715;391;128085;5061.839412;1236.909129;23436;100928;50.287926%;59964.832030;5644.844189;14.595833%;19.394167%;123706;0;7313;0.1%;0.1%;0.1%;0.1%;0.1%;0.1%;100.0%;0.00%;0.00%;0.00%;0.00%;0.00%;0.00%;0.01%;0.02%;0.05%;0.16%;6.04%;40.40%;52.68%;0.64%;0.01%;0.00%;0.01%;0.00%;0.00%;0.00%;0.00%;0.00%
A description of this job goes here.
The job description (if provided) follows on a second line.
To enable terse output, use the --minimal command line option. The first
value is the version of the terse output format. If the output has to
be changed for some reason, this number will be incremented by 1 to
signify that change.
Split up, the format is as follows:
terse version, fio version, jobname,
groupid, error
READ status:
Total IO (KB), bandwidth
(KB/sec), IOPS, runtime (msec)
Submission latency: min, max,
mean, deviation (usec)
Completion latency: min, max,
mean, deviation (usec)
Completion latency
percentiles: 20 fields (see below)
Total latency: min, max, mean,
deviation (usec)
Bw (KB/s): min, max, aggregate
percentage of total, mean, deviation
WRITE status:
Total IO (KB), bandwidth
(KB/sec), IOPS, runtime (msec)
Submission latency: min, max,
mean, deviation (usec)
Completion latency: min, max,
mean, deviation (usec)
Completion latency
percentiles: 20 fields (see below)
Total latency: min, max, mean,
deviation (usec)
Bw (KB/s): min, max, aggregate
percentage of total, mean, deviation
CPU usage: user, system, context
switches, major faults, minor faults
IO depths: <=1, 2, 4, 8, 16, 32,
>=64
IO latencies microseconds: <=2,
4, 10, 20, 50, 100, 250, 500, 750, 1000
IO latencies milliseconds: <=2,
4, 10, 20, 50, 100, 250, 500, 750, 1000, 2000, >=2000
Disk utilization: Disk name, Read
ios, write ios,
Read merges, write merges,
Read ticks, write ticks,
Time spent in queue, disk utilization
percentage
Additional Info (dependent on
continue_on_error, default off): total # errors, first error code
Additional Info (dependent on
description being set): Text description
Completion latency percentiles can be a grouping of up to 20 sets, so
for the terse output fio writes all of them. Each field will look like
this:
1.00%=6112
which is the Xth percentile, and the usec latency associated with it.
For disk utilization, all disks used by fio are shown. So for each disk
there will be a disk utilization section.
8.0 Trace file format
---------------------
There are two trace file format that you can encounter. The older (v1)
format
is unsupported since version 1.20-rc3 (March 2008). It will still be
described
below in case that you get an old trace and want to understand it.
In any case the trace is a simple text file with a single action per
line.
8.1 Trace file format v1
------------------------
Each line represents a single io action in the following format:
rw, offset, length
where rw=0/1 for read/write, and the offset and length entries being in
bytes.
This format is not supported in Fio versions => 1.20-rc3.
8.2 Trace file format v2
------------------------
The second version of the trace file format was added in Fio version
1.17.
It allows to access more then one file per trace and has a bigger set of
possible file actions.
The first line of the trace file has to be:
fio version 2 iolog
Following this can be lines in two different formats, which are described
below.
The file management format:
filename action
The filename is given as an absolute path. The action can be one of
these:
add Add the given filename to the trace
open Open the file with the given
filename. The filename has to have
been added with the add
action before.
close Close the file with the
given filename. The file has to have been
opened before.
The file io action format:
filename action offset length
The filename is given as an absolute path, and has to have been added and
opened
before it can be used with this format. The offset and length are given
in
bytes. The action can be one of these:
wait Wait for 'offset'
microseconds. Everything below 100 is discarded.
read Read 'length' bytes beginning
from 'offset'
write Write 'length' bytes beginning
from 'offset'
sync fsync() the file
datasync fdatasync() the file
trim trim the given file from the
given 'offset' for 'length' bytes
9.0 CPU idleness profiling
--------------------------
In some cases, we want to understand CPU overhead in a test. For example,
we test patches for the specific goodness of whether they reduce CPU
usage.
fio implements a balloon approach to create a thread per CPU that runs at
idle priority, meaning that it only runs when nobody else needs the cpu.
By measuring the amount of work completed by the thread, idleness of each
CPU can be derived accordingly.
An unit work is defined as touching a full page of unsigned characters.
Mean
and standard deviation of time to complete an unit work is reported in
"unit
work" section. Options can be chosen to report detailed percpu idleness
or
overall system idleness by aggregating percpu stats.
