X-Git-Url: https://git.kernel.dk/?a=blobdiff_plain;f=HOWTO;h=64453489175aec0346e8e8f7df9422849582fc12;hb=8d916c942bb088204ab5c0438c297903c9160698;hp=c9c1d8c6d657dbb81dec21c88be5622aeac9b4e9;hpb=135be493d843d4cae2966a35cbd22a3058ec8e4b;p=fio.git diff --git a/HOWTO b/HOWTO index c9c1d8c6..64453489 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 ------------------------ @@ -272,17 +273,43 @@ filename=str Fio normally makes up a filename based on the job name, 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=/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. @@ -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: @@ -353,6 +375,12 @@ kb_base=int The base unit for a kilobyte. The defacto base is 2^10, 1024. 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. @@ -403,7 +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. @@ -769,7 +797,7 @@ 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 @@ -1213,6 +1241,7 @@ 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). @@ -1395,6 +1424,9 @@ 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 @@ -1568,6 +1600,9 @@ 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 @@ -1686,3 +1721,18 @@ 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.