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From 8e318fd65ba5c0f6ce82860984bc8d69a7843f97 Mon Sep 17 00:00:00 2001
From: Ankit Kumar <ankit.kumar@samsung.com>
Date: Tue, 16 Aug 2022 11:08:21 +0530
Subject: [PATCH] doc: update fio doc for xnvme engine
- Elaborate about the various sync, async and admin
interfaces.
- add missing io_uring_cmd async backend entry.
- xnvme ioengine doesn't support file stat.
Signed-off-by: Ankit Kumar <ankit.kumar@samsung.com>
Link: https://lore.kernel.org/r/20220816053821.440-3-ankit.kumar@samsung.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
HOWTO.rst | 37 ++++++++++++++++++++++++++-----------
fio.1 | 34 +++++++++++++++++++++-------------
2 files changed, 47 insertions(+), 24 deletions(-)
diff --git a/HOWTO.rst b/HOWTO.rst
index 05fc117f..b2750b56 100644
--- a/HOWTO.rst
+++ b/HOWTO.rst
@@ -2780,41 +2780,56 @@ with the caveat that when used on the command line, they must come after the
Select the xnvme async command interface. This can take these values.
**emu**
- This is default and used to emulate asynchronous I/O.
+ This is default and use to emulate asynchronous I/O by using a
+ single thread to create a queue pair on top of a synchronous
+ I/O interface using the NVMe driver IOCTL.
**thrpool**
- Use thread pool for Asynchronous I/O.
+ Emulate an asynchronous I/O interface with a pool of userspace
+ threads on top of a synchronous I/O interface using the NVMe
+ driver IOCTL. By default four threads are used.
**io_uring**
- Use Linux io_uring/liburing for Asynchronous I/O.
+ Linux native asynchronous I/O interface which supports both
+ direct and buffered I/O.
+ **io_uring_cmd**
+ Fast Linux native asynchronous I/O interface for NVMe pass
+ through commands. This only works with NVMe character device
+ (/dev/ngXnY).
**libaio**
Use Linux aio for Asynchronous I/O.
**posix**
- Use POSIX aio for Asynchronous I/O.
+ Use the posix asynchronous I/O interface to perform one or
+ more I/O operations asynchronously.
**nil**
- Use nil-io; For introspective perf. evaluation
+ Do not transfer any data; just pretend to. This is mainly used
+ for introspective performance evaluation.
.. option:: xnvme_sync=str : [xnvme]
Select the xnvme synchronous command interface. This can take these values.
**nvme**
- This is default and uses Linux NVMe Driver ioctl() for synchronous I/O.
+ This is default and uses Linux NVMe Driver ioctl() for
+ synchronous I/O.
**psync**
- Use pread()/write() for synchronous I/O.
+ This supports regular as well as vectored pread() and pwrite()
+ commands.
+ **block**
+ This is the same as psync except that it also supports zone
+ management commands using Linux block layer IOCTLs.
.. option:: xnvme_admin=str : [xnvme]
Select the xnvme admin command interface. This can take these values.
**nvme**
- This is default and uses linux NVMe Driver ioctl() for admin commands.
+ This is default and uses linux NVMe Driver ioctl() for admin
+ commands.
**block**
Use Linux Block Layer ioctl() and sysfs for admin commands.
- **file_as_ns**
- Use file-stat to construct NVMe idfy responses.
.. option:: xnvme_dev_nsid=int : [xnvme]
- xnvme namespace identifier, for userspace NVMe driver.
+ xnvme namespace identifier for userspace NVMe driver, such as SPDK.
.. option:: xnvme_iovec=int : [xnvme]
diff --git a/fio.1 b/fio.1
index 6630525f..f3f3dc5d 100644
--- a/fio.1
+++ b/fio.1
@@ -2530,22 +2530,29 @@ Select the xnvme async command interface. This can take these values.
.RS
.TP
.B emu
-This is default and used to emulate asynchronous I/O
+This is default and use to emulate asynchronous I/O by using a single thread to
+create a queue pair on top of a synchronous I/O interface using the NVMe driver
+IOCTL.
.TP
.BI thrpool
-Use thread pool for Asynchronous I/O
+Emulate an asynchronous I/O interface with a pool of userspace threads on top
+of a synchronous I/O interface using the NVMe driver IOCTL. By default four
+threads are used.
.TP
.BI io_uring
-Use Linux io_uring/liburing for Asynchronous I/O
+Linux native asynchronous I/O interface which supports both direct and buffered
+I/O.
.TP
.BI libaio
Use Linux aio for Asynchronous I/O
.TP
.BI posix
-Use POSIX aio for Asynchronous I/O
+Use the posix asynchronous I/O interface to perform one or more I/O operations
+asynchronously.
.TP
.BI nil
-Use nil-io; For introspective perf. evaluation
+Do not transfer any data; just pretend to. This is mainly used for
+introspective performance evaluation.
.RE
.RE
.TP
@@ -2555,10 +2562,14 @@ Select the xnvme synchronous command interface. This can take these values.
.RS
.TP
.B nvme
-This is default and uses Linux NVMe Driver ioctl() for synchronous I/O
+This is default and uses Linux NVMe Driver ioctl() for synchronous I/O.
.TP
.BI psync
-Use pread()/write() for synchronous I/O
+This supports regular as well as vectored pread() and pwrite() commands.
+.TP
+.BI block
+This is the same as psync except that it also supports zone management
+commands using Linux block layer IOCTLs.
.RE
.RE
.TP
@@ -2568,18 +2579,15 @@ Select the xnvme admin command interface. This can take these values.
.RS
.TP
.B nvme
-This is default and uses Linux NVMe Driver ioctl() for admin commands
+This is default and uses Linux NVMe Driver ioctl() for admin commands.
.TP
.BI block
-Use Linux Block Layer ioctl() and sysfs for admin commands
-.TP
-.BI file_as_ns
-Use file-stat as to construct NVMe idfy responses
+Use Linux Block Layer ioctl() and sysfs for admin commands.
.RE
.RE
.TP
.BI (xnvme)xnvme_dev_nsid\fR=\fPint
-xnvme namespace identifier, for userspace NVMe driver.
+xnvme namespace identifier for userspace NVMe driver such as SPDK.
.TP
.BI (xnvme)xnvme_iovec
If this option is set, xnvme will use vectored read/write commands.
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