Hi, I just stumbled into a glaring pitfall when playing with iodepth=X for the first time. Was using ioengine=sync (default), increased iodepth > 1 and wondered briefly why my results didn't change. Thinking about it, this made perfect sense and the "IO depths" distribution in the result summary even pointed me to it. Nevertheless, it might help others to avoid this alltogether if the man page paragraph on iodepth would include a small heads up / reference to ioengines. Example patch attached, not quite sure about the wording for the verify_async aspect. Sebastian
--- Begin Message ---
- Subject: [PATCH] fio.1: Add ioengines heads up to the iodepth section
- From: Sebastian Kayser <sebastian@xxxxxxxxxx>
- Date: Wed, 1 Dec 2010 22:28:47 +0100
--- fio.1 | 4 +++- 1 files changed, 3 insertions(+), 1 deletions(-) diff --git a/fio.1 b/fio.1 index b0276c4..ab147f2 100644 --- a/fio.1 +++ b/fio.1 @@ -379,7 +379,9 @@ Loads an external I/O engine object file. Append the engine filename as .RE .TP .BI iodepth \fR=\fPint -Number of I/O units to keep in flight against the file. Default: 1. +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. .TP .BI iodepth_batch \fR=\fPint Number of I/Os to submit at once. Default: \fBiodepth\fR. -- 1.4.4.4
--- End Message ---
