Merge branch 'master' into gfio

[fio.git] / HOWTO

diff --git a/HOWTO b/HOWTO
index c9c1d8c6d657dbb81dec21c88be5622aeac9b4e9..f7948c3f1d8e676227374a713a35ccec5bbd9784 100644 (file)
--- a/HOWTO
+++ b/HOWTO
@@ -272,17 +272,17 @@ 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.
 
 opendir=str    Tell fio to recursively add any file it can find in this
                directory and down the file system tree.
@@ -353,6 +353,12 @@ 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.
 
@@ -1686,3 +1692,18 @@ 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.