t/zbd: Support testing zone capacity smaller than zone size with null_blk

[fio.git] / HOWTO

diff --git a/HOWTO b/HOWTO
index 9e71a6197bb47000db195fcdc5e09cc0f70b2d51..35ead0cb7fd4f58d2aa8a1d98d9341b50b121e35 100644 (file)
--- a/HOWTO
+++ b/HOWTO
@@ -970,14 +970,15 @@ Target file/device
        Accepted values are:
 
                **none**
-                               The :option:`zonerange`, :option:`zonesize` and
-                               :option:`zoneskip` parameters are ignored.
+                               The :option:`zonerange`, :option:`zonesize`,
+                               :option `zonecapacity` and option:`zoneskip`
+                               parameters are ignored.
                **strided**
                                I/O happens in a single zone until
                                :option:`zonesize` bytes have been transferred.
                                After that number of bytes has been
                                transferred processing of the next zone
-                               starts.
+                               starts. :option `zonecapacity` is ignored.
                **zbd**
                                Zoned block device mode. I/O happens
                                sequentially in each zone, even if random I/O
@@ -1004,6 +1005,17 @@ Target file/device
        For :option:`zonemode` =zbd, this is the size of a single zone. The
        :option:`zonerange` parameter is ignored in this mode.
 
+
+.. option:: zonecapacity=int
+
+       For :option:`zonemode` =zbd, this defines the capacity of a single zone,
+       which is the accessible area starting from the zone start address.
+       This parameter only applies when using :option:`zonemode` =zbd in
+       combination with regular block devices. If not specified it defaults to
+       the zone size. If the target device is a zoned block device, the zone
+       capacity is obtained from the device information and this option is
+       ignored.
+
 .. option:: zoneskip=int
 
        For :option:`zonemode` =strided, the number of bytes to skip after
@@ -2097,6 +2109,26 @@ 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
@@ -4145,7 +4177,7 @@ Fio supports a variety of log file formats, for logging latencies, bandwidth,
 and IOPS. The logs share a common format, which looks like this:
 
     *time* (`msec`), *value*, *data direction*, *block size* (`bytes`),
-    *offset* (`bytes`)
+    *offset* (`bytes`), *command priority*
 
 *Time* for the log entry is always in milliseconds. The *value* logged depends
 on the type of log, it will be one of the following:
@@ -4170,6 +4202,9 @@ The entry's *block size* is always in bytes. The *offset* is the position in byt
 from the start of the file for that particular I/O. The logging of the offset can be
 toggled with :option:`log_offset`.
 
+*Command priority* is 0 for normal priority and 1 for high priority. This is controlled
+by the ioengine specific :option:`cmdprio_percentage`.
+
 Fio defaults to logging every individual I/O but when windowed logging is set
 through :option:`log_avg_msec`, either the average (by default) or the maximum
 (:option:`log_max_value` is set) *value* seen over the specified period of time