doc: update about sqthread_poll

Update that when sqthread_poll is enabled fio will not report submission
latency.

Signed-off-by: Ankit Kumar <ankit.kumar@samsung.com>
Signed-off-by: Vincent Fu <vincent.fu@samsung.com>

diff --git a/HOWTO.rst b/HOWTO.rst
index bcc3da3a9c77160f41234bff9927656038c35218..4419ee1b0855465d7a1ec7874c0b8b8010436115 100644 (file)
--- a/HOWTO.rst
+++ b/HOWTO.rst
@@ -2299,7 +2299,9 @@ with the caveat that when used on the command line, they must come after 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.
+       system. As submission is just the time it takes to fill in the sqe
+       entries and any syscall required to wake up the idle kernel thread,
+       fio will not report submission latencies.
 
 .. option:: sqthread_poll_cpu=int : [io_uring] [io_uring_cmd]
 

diff --git a/fio.1 b/fio.1
index 9e33c9e18925811e99f38dc67ca92f7f89e4a37d..a156bf5d4eb377889635f123cd0c0eb7523240ac 100644 (file)
--- a/fio.1
+++ b/fio.1
@@ -2090,7 +2090,9 @@ sqthread_poll option.
 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.
+the cost of using more CPU in the system. As submission is just the time it
+takes to fill in the sqe entries and any syscall required to wake up the idle
+kernel thread, fio will not report submission latencies.
 .TP
 .BI (io_uring,io_uring_cmd)sqthread_poll_cpu \fR=\fPint
 When `sqthread_poll` is set, this option provides a way to define which CPU