X-Git-Url: https://git.kernel.dk/?p=fio.git;a=blobdiff_plain;f=HOWTO;h=4fd025126925eb6fd75910608530b8f8c20ba27f;hp=8073240ef14074b5007bafa4296b913f1951f647;hb=fdc0f3b646e417497849d4398029f780b0e5262f;hpb=771e58befea806d2d881953050c4e65329eee382 diff --git a/HOWTO b/HOWTO index 8073240e..4fd02512 100644 --- a/HOWTO +++ b/HOWTO @@ -9,6 +9,7 @@ Table of contents 6. Normal output 7. Terse output 8. Trace file format +9. CPU idleness profiling 1.0 Overview and history ------------------------ @@ -284,6 +285,32 @@ filename=str Fio normally makes up a filename based on the job name, 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. @@ -301,11 +328,6 @@ lockfile=str Fio defaults to not locking any files before it does 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: @@ -409,7 +431,7 @@ filesize=int Individual file sizes. May be a range, in which case fio 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. @@ -546,6 +568,8 @@ ioengine=str Defines how the job issues io to the file. The following 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). @@ -744,6 +768,17 @@ random_distribution=str:float By default, fio will use a completely uniform 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. + +percentage_sequential=int See percentage_random. It is guaranteed that + they add up to 100. The later setting has priority, each + will adjust the other. + 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 @@ -775,7 +810,7 @@ random_generator=str Fio supports the following engines for generating 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 @@ -795,11 +830,15 @@ thinktime_spin=int to sleeping for the rest of the period specified by thinktime. -thinktime_blocks +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. + 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 @@ -1197,7 +1236,7 @@ write_lat_log=str Same as write_bw_log, except that this option stores io write_lat_log=foo - The actual log names will be foo_slat.log, foo_slat.log, + 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. @@ -1219,22 +1258,19 @@ log_avg_msec=int By default, fio will log an entry in the iops, latency, 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). + 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). + 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. -cpuload=int If the job is a CPU cycle eater, attempt to use the specified - percentage of CPU cycles. - -cpuchunks=int If the job is a CPU cycle eater, split the load into - cycles of the given time. In microseconds. - disk_util=bool Generate disk utilization statistics, if the platform supports it. Defaults to on. @@ -1394,6 +1430,11 @@ that defines them is selected. 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. + [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 @@ -1402,6 +1443,9 @@ that defines them is selected. [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 @@ -1575,6 +1619,9 @@ util= The disk utilization. A value of 100% means we kept the disk 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 @@ -1693,3 +1740,18 @@ 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.