- 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@xxxxxxxxxxx> --- 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. -- 2.17.1
