6. Normal output
7. Terse output
8. Trace file format
+9. CPU idleness profiling
1.0 Overview and history
------------------------
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.
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. 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=/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.
same time, but writes get exclusive
access.
- The option may be post-fixed with a lock batch number. If
- set, then each thread/process may do that amount of IOs to
- the file before giving up the lock. Since lock acquisition is
- expensive, batching the lock/unlocks will speed up IO.
-
readwrite=str
rw=str Type of io pattern. Accepted values are:
write Sequential writes
randwrite Random writes
randread Random reads
- rw Sequential mixed reads and writes
+ 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.
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
- postfix is used with a sequential IO pattern, then the value
+ 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.
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.
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
+ 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.
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.
+
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
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
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.
buffered=bool If value is true, use buffered io. This is the opposite
of the 'direct' option. Defaults to true.
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.
+
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
fdatasync=int Like fsync= but uses fdatasync() to only sync data and not
metadata blocks.
- In FreeBSD there is no fdatasync(), this falls back to
+ 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
and is large enough for the specified write phase, nothing
will be done.
-end_fsync=bool If true, fsync file contents when the job exits.
+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
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.
+
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
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
the job to exit. The same format as rate is used for read vs
write seperation.
+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.
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.
+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
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
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 preceeding 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. If this option isn't given,
- jobs in a file will be part of the same reporting group
- unless separated by a stone wall (or if it's a group
- by itself, with the numjobs option).
+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. We regard that grouping of jobs as a
- specific group.
-
-group_reporting If 'numjobs' is set, it may be interesting to display
- statistics for the group as a whole instead of for each
- individual job. This is especially true of 'numjobs' is
- large, looking at individual thread/process output quickly
- becomes unwieldy. If 'group_reporting' is specified, fio
- will show the final report per-group instead of per-job.
+ 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
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
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_log_log for behaviour of given
- filename. For this option, the postfix is _bw.log.
+ 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
write_bw_log=str If given, write an IOPS log of the jobs in this job
file. See write_bw_log.
+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).
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
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
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
[netsplice] port=int
[net] port=int The TCP or UDP port to bind to or connect to.
+[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
- udp Unreliable datagram protocol
+ udp User datagram protocol
unix UNIX domain socket
When the protocol is TCP or UDP, the port must also be given,
[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 Normal 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.
+
+[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
---- ---
P Thread setup, but not started.
C Thread created.
-I Thread initialized, waiting.
+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.
F Running, currently waiting for fsync()
V Running, doing verification of written data.
E Thread exited, not reaped by main thread yet.
-_ Thread reaped.
+_ 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).
+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
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.
+ 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,
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.
+
7.0 Terse output
----------------
terse version, fio version, jobname, groupid, error
READ status:
Total IO (KB), bandwidth (KB/sec), IOPS, runtime (msec)
- Submission latency: min, max, mean, deviation
- Completion latency: min, max, mean, deviation
+ 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
- Bw: min, max, aggregate percentage of total, mean, deviation
+ 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
- Completion latency: min, max, mean, deviation
+ 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
- Bw: min, max, aggregate percentage of total, mean, deviation
+ 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
Read merges, write merges,
Read ticks, write ticks,
Time spent in queue, disk utilization percentage
- Additional Info (dependant on continue_on_error, default off): total # errors, first error code
-
+ Additional Info (dependant on continue_on_error, default off): total # errors, first error code
+
Additional Info (dependant on description being set): Text description
Completion latency percentiles can be a grouping of up to 20 sets, so
8.0 Trace file format
---------------------
-There are two trace file format that you can encounter. The older (v1) 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.
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
+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.
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
+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.
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.
projects / fio.git / blobdiff