Document that write_iolog is unsafe for concurrent jobs
The write_iolog parameter should not be used in the global section since
each job will independently write to the same file. The output will be
interspersed and the file will be corrupt.
Document that each job should write to its own iolog file. This will
save users time when trying out the iolog feature for the first time.
Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
Updated by me to make the same change to the man page.
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
diff --git a/HOWTO b/HOWTO
index dc21afc..7c94329 100644
--- a/HOWTO
+++ b/HOWTO
@@ -988,7 +988,8 @@
io on zones of a file.
write_iolog=str Write the issued io patterns to the specified file. See
- read_iolog.
+ read_iolog. Specify a separate file for each job, otherwise
+ the iologs will be interspersed and the file may be corrupt.
read_iolog=str Open an iolog with the specified file name and replay the
io patterns it contains. This can be used to store a
diff --git a/README b/README
index 0f91c66..de06fb1 100644
--- a/README
+++ b/README
@@ -274,7 +274,9 @@
and length entries being in bytes.
write_iolog=x Write an iolog to file 'x' in the same format as iolog.
The iolog options are exclusive, if both given the
- read iolog will be performed.
+ read iolog will be performed. Specify a separate file
+ for each job, otherwise the iologs will be interspersed
+ and the file may be corrupt.
write_bw_log Write a bandwidth log.
write_lat_log Write a latency log.
lockmem=x Lock down x amount of memory on the machine, to
diff --git a/fio.1 b/fio.1
index eaa1c40..1f1116c 100644
--- a/fio.1
+++ b/fio.1
@@ -743,7 +743,9 @@
read.
.TP
.BI write_iolog \fR=\fPstr
-Write the issued I/O patterns to the specified file.
+Write the issued I/O patterns to the specified file. Specify a separate file
+for each job, otherwise the iologs will be interspersed and the file may be
+corrupt.
.TP
.BI read_iolog \fR=\fPstr
Replay the I/O patterns contained in the specified file generated by