Update that when sqthread_poll is enabled the submission and completion latencies reported may not be accurate. This is because the actual submission is done by the kernel polling thread. Signed-off-by: Ankit Kumar <ankit.kumar@xxxxxxxxxxx> --- HOWTO.rst | 4 +++- fio.1 | 4 +++- 2 files changed, 6 insertions(+), 2 deletions(-) diff --git a/HOWTO.rst b/HOWTO.rst index 0fb5593e..dea625fe 100644 --- 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. The submission and completion latencies reported may not be + accurate as fio has no idea when the kernel polling thread submits the + actual I/O. .. option:: sqthread_poll_cpu : [io_uring] [io_uring_cmd] diff --git a/fio.1 b/fio.1 index 4324a975..95c5ce55 100644 --- 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. The submission and completion +latencies reported may not be accurate as fio has no idea when the kernel +polling thread submits the actual I/O. .TP .BI (io_uring,io_uring_cmd)sqthread_poll_cpu When `sqthread_poll` is set, this option provides a way to define which CPU -- 2.17.1
