From ee72ca09d4657f6a805c113d9bc43428f4b28a89 Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Thu, 2 Dec 2010 20:05:37 +0100 Subject: [PATCH] Sync HOWTO iodepth option with man page Also add a note on other restrictions that may cause lower IO depth than expected. Signed-off-by: Jens Axboe --- HOWTO | 9 ++++++++- fio.1 | 6 +++++- 2 files changed, 13 insertions(+), 2 deletions(-) diff --git a/HOWTO b/HOWTO index 7cb24dd8..dc21afc0 100644 --- a/HOWTO +++ b/HOWTO @@ -549,7 +549,14 @@ ioengine=str Defines how the job issues io to the file. The following iodepth=int This defines how many io units to keep in flight against the file. The default is 1 for each file defined in this job, can be overridden with a larger value for higher - concurrency. + concurrency. Note that increasing iodepth beyond 1 will not + affect synchronous ioengines (except for small degress when + verify_async is in use). Even async engines my impose OS + restrictions causing the desired depth not to be achieved. + This may happen on Linux when using libaio and not setting + direct=1, since buffered IO is not async on that OS. Keep an + eye on the IO depth distribution in the fio output to verify + that the achieved depth is as expected. Default: 1. iodepth_batch_submit=int iodepth_batch=int This defines how many pieces of IO to submit at once. diff --git a/fio.1 b/fio.1 index ab147f28..eaa1c408 100644 --- a/fio.1 +++ b/fio.1 @@ -381,7 +381,11 @@ Loads an external I/O engine object file. Append the engine filename as .BI iodepth \fR=\fPint Number of I/O units to keep in flight against the file. Note that increasing iodepth beyond 1 will not affect synchronous ioengines (except for small -degress when verify_async is in use). Default: 1. +degress when verify_async is in use). Even async engines my impose OS +restrictions causing the desired depth not to be achieved. This may happen on +Linux when using libaio and not setting \fBdirect\fR=1, since buffered IO is +not async on that OS. Keep an eye on the IO depth distribution in the +fio output to verify that the achieved depth is as expected. Default: 1. .TP .BI iodepth_batch \fR=\fPint Number of I/Os to submit at once. Default: \fBiodepth\fR. -- 2.25.1