Documentation update

[fio.git] / HOWTO

diff --git a/HOWTO b/HOWTO
index 9bfa437833d0703e2ee10cac8501c6d40a521d3d..2be845c4add2f7ce6c7cebc4d95ca9ce9083622a 100644 (file)
--- a/HOWTO
+++ b/HOWTO
@@ -546,7 +546,9 @@ 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.
+               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.
 
 norandommap    Normally fio will cover every block of the file when doing
                random IO. If this option is given, fio will just get a
@@ -588,19 +590,29 @@ thinktime_blocks
                defaults to 1 which will make fio wait 'thinktime' usecs
                after every block.
 
-rate=int       Cap the bandwidth used by this job to this number of KiB/sec.
+rate=int       Cap the bandwidth used by this job. The number is in bytes/sec,
+               the normal postfix 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 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 smallest block size is used as the metric. The same format
+               as rate is used for read vs write seperation.
 
 rate_iops_min=int If fio doesn't meet this rate of IO, it will cause
-               the job to exit.
+               the job to exit. The same format as rate is used for read vs
+               write seperation.
 
 ratecycle=int  Average bandwidth for 'rate' and 'ratemin' over this number
                of milliseconds.
@@ -713,6 +725,11 @@ create_fsync=bool  fsync the data file after creation. This is the
 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.
 
+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.
+
 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.
@@ -928,6 +945,7 @@ Idle        Run
 P              Thread setup, but not started.
 C              Thread created.
 I              Thread initialized, waiting.
+       p       Thread running pre-reading file(s).
        R       Running, doing sequential reads.
        r       Running, doing random reads.
        W       Running, doing sequential writes.