docs: small HOWTO fixes

[fio.git] / HOWTO

diff --git a/HOWTO b/HOWTO
index 142b83e5020f9b77303756354c9a3ef8cdbaa682..1c9b2c1020f7e7d53b43926fcb3c3369a1db07f8 100644 (file)
--- a/HOWTO
+++ b/HOWTO
@@ -93,6 +93,12 @@ Command line options
                        Dump info related to I/O rate switching.
        *compress*
                        Dump info related to log compress/decompress.
+       *steadystate*
+                       Dump info related to steadystate detection.
+       *helperthread*
+                       Dump info related to the helper thread.
+       *zbd*
+                       Dump info related to support for zoned block devices.
        *?* or *help*
                        Show available debug options.
 
@@ -1805,6 +1811,11 @@ I/O engine
                **pvsync2**
                        Basic :manpage:`preadv2(2)` or :manpage:`pwritev2(2)` I/O.
 
+               **io_uring**
+                       Fast Linux native asynchronous I/O. Supports async IO
+                       for both direct and buffered IO.
+                       This engine defines engine specific options.
+
                **libaio**
                        Linux native asynchronous I/O. Note that Linux may only support
                        queued behavior with non-buffered I/O (set ``direct=1`` or
@@ -1993,6 +2004,8 @@ I/O engine
                        requests for IME. FIO will then decide when to commit these requests.
                **libiscsi**
                        Read and write iscsi lun with libiscsi.
+               **nbd**
+                       Read and write a Network Block Device (NBD).
 
 I/O engine specific parameters
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
@@ -2002,6 +2015,35 @@ In addition, there are some parameters which are only valid when a specific
 with the caveat that when used on the command line, they must come after the
 :option:`ioengine` that defines them is selected.
 
+.. option:: hipri : [io_uring]
+
+       If this option is set, fio will attempt to use polled IO completions.
+       Normal IO completions generate interrupts to signal the completion of
+       IO, polled completions do not. Hence they are require active reaping
+       by the application. The benefits are more efficient IO for high IOPS
+       scenarios, and lower latencies for low queue depth IO.
+
+.. option:: fixedbufs : [io_uring]
+
+       If fio is asked to do direct IO, then Linux will map pages for each
+       IO call, and release them when IO is done. If this option is set, the
+       pages are pre-mapped before IO is started. This eliminates the need to
+       map and release for each IO. This is more efficient, and reduces the
+       IO latency as well.
+
+.. option:: sqthread_poll : [io_uring]
+
+       Normally fio will submit IO by issuing a system call to notify the
+       kernel of available items in the SQ ring. If this option is set, the
+       act of submitting IO will be done by a polling thread in the kernel.
+       This frees up cycles for fio, at the cost of using more CPU in the
+       system.
+
+.. option:: sqthread_poll_cpu : [io_uring]
+
+       When :option:`sqthread_poll` is set, this option provides a way to
+       define which CPU should be used for the polling thread.
+
 .. option:: userspace_reap : [libaio]
 
        Normally, with the libaio engine in use, fio will use the
@@ -2265,6 +2307,15 @@ with the caveat that when used on the command line, they must come after the
        turns on verbose logging from libcurl, 2 additionally enables
        HTTP IO tracing. Default is **0**
 
+.. option:: uri=str : [nbd]
+
+       Specify the NBD URI of the server to test.  The string
+       is a standard NBD URI
+       (see https://github.com/NetworkBlockDevice/nbd/tree/master/doc).
+       Example URIs: nbd://localhost:10809
+       nbd+unix:///?socket=/tmp/socket
+       nbds://tlshost/exportname
+
 I/O depth
 ~~~~~~~~~
 
@@ -2343,7 +2394,7 @@ I/O depth
        this option can reduce both performance and the :option:`iodepth` achieved.
 
        This option only applies to I/Os issued for a single job except when it is
-       enabled along with :option:`io_submit_mode`=offload. In offload mode, fio
+       enabled along with :option:`io_submit_mode`\=offload. In offload mode, fio
        will check for overlap among all I/Os submitted by offload jobs with :option:`serialize_overlap`
        enabled.