X-Git-Url: https://git.kernel.dk/?a=blobdiff_plain;f=HOWTO;h=9e339bb8d0a608a2f83b141197bd1bbbb503804b;hb=d87d9c6c611f74a5888c74568d545be200139498;hp=0a3661684fb4653a1638b30e7d1e204abe6094a9;hpb=b2a432bfbb6d10e93f2c8f8092d6db672d45af0d;p=fio.git

diff --git a/HOWTO b/HOWTO
index 0a366168..9e339bb8 100644
--- a/HOWTO
+++ b/HOWTO
@@ -2040,7 +2040,8 @@ with the caveat that when used on the command line, they must come after the
     the priority bit. Non-read I/O is likely unaffected by ``cmdprio_percentage``.
     This option cannot be used with the `prio` or `prioclass` options. For this
     option to set the priority bit properly, NCQ priority must be supported and
-    enabled and :option:`direct`\=1 option must be used.
+    enabled and :option:`direct`\=1 option must be used. fio must also be run as
+    the root user.
 
 .. option:: fixedbufs : [io_uring]
 
@@ -2096,6 +2097,26 @@ with the caveat that when used on the command line, they must come after the
 	When hipri is set this determines the probability of a pvsync2 I/O being high
 	priority. The default is 100%.
 
+.. option:: nowait : [pvsync2] [libaio] [io_uring]
+
+	By default if a request cannot be executed immediately (e.g. resource starvation,
+	waiting on locks) it is queued and the initiating process will be blocked until
+	the required resource becomes free.
+
+	This option sets the RWF_NOWAIT flag (supported from the 4.14 Linux kernel) and
+	the call will return instantly with EAGAIN or a partial result rather than waiting.
+
+	It is useful to also use ignore_error=EAGAIN when using this option.
+
+	Note: glibc 2.27, 2.28 have a bug in syscall wrappers preadv2, pwritev2.
+	They return EOPNOTSUP instead of EAGAIN.
+
+	For cached I/O, using this option usually means a request operates only with
+	cached data. Currently the RWF_NOWAIT flag does not supported for cached write.
+
+	For direct I/O, requests will only succeed if cache invalidation isn't required,
+	file blocks are fully allocated and the disk request could be issued immediately.
+
 .. option:: cpuload=int : [cpuio]
 
 	Attempt to use the specified percentage of CPU cycles. This is a mandatory
@@ -2261,6 +2282,11 @@ with the caveat that when used on the command line, they must come after the
 	multiple paths exist between the client and the server or in certain loopback
 	configurations.
 
+.. option:: stat_type=str : [filestat]
+
+	Specify stat system call type to measure lookup/getattr performance.
+	Default is **stat** for :manpage:`stat(2)`.
+
 .. option:: readfua=bool : [sg]
 
 	With readfua option set to 1, read operations include
@@ -2546,6 +2572,13 @@ I/O latency
 	defaults to 100.0, meaning that all I/Os must be equal or below to the value
 	set by :option:`latency_target`.
 
+.. option:: latency_run=bool
+
+	Used with :option:`latency_target`. If false (default), fio will find
+	the highest queue depth that meets :option:`latency_target` and exit. If
+	true, fio will continue running and try to meet :option:`latency_target`
+	by adjusting queue depth.
+
 .. option:: max_latency=time
 
 	If set, fio will exit the job with an ETIMEDOUT error if it exceeds this
@@ -3342,27 +3375,28 @@ Measurements and reporting
 	Disable measurements of throughput/bandwidth numbers. See
 	:option:`disable_lat`.
 
+.. option:: slat_percentiles=bool
+
+	Report submission latency percentiles. Submission latency is not recorded
+	for synchronous ioengines.
+
 .. option:: clat_percentiles=bool
 
-	Enable the reporting of percentiles of completion latencies.  This
-	option is mutually exclusive with :option:`lat_percentiles`.
+	Report completion latency percentiles.
 
 .. option:: lat_percentiles=bool
 
-	Enable the reporting of percentiles of I/O latencies. This is similar
-	to :option:`clat_percentiles`, except that this includes the
-	submission latency. This option is mutually exclusive with
-	:option:`clat_percentiles`.
+	Report total latency percentiles. Total latency is the sum of submission
+	latency and completion latency.
 
 .. option:: percentile_list=float_list
 
-	Overwrite the default list of percentiles for completion latencies and
-	the block error histogram.  Each number is a floating number in the
-	range (0,100], and the maximum length of the list is 20. Use ``:`` to
-	separate the numbers, and list the numbers in ascending order. For
+	Overwrite the default list of percentiles for latencies and the block error
+	histogram.  Each number is a floating point number in the range (0,100], and
+	the maximum length of the list is 20. Use ``:`` to separate the numbers. For
 	example, ``--percentile_list=99.5:99.9`` will cause fio to report the
-	values of completion latency below which 99.5% and 99.9% of the observed
-	latencies fell, respectively.
+	latency durations below which 99.5% and 99.9% of the observed latencies fell,
+	respectively.
 
 .. option:: significant_figures=int