[PATCH v3 3/3] iolog: update man page for version 3

[Mohamad Gebai <mogeb@fb.com>]

Add documentation for iolog version 3, mainly the differences between
versions 2 and 3.

Signed-off-by: Mohamad Gebai <mogeb@fb.com>
---
 HOWTO.rst | 29 ++++++++++++++++++++++++++++-
 fio.1     | 35 ++++++++++++++++++++++++++++++++++-
 2 files changed, 62 insertions(+), 2 deletions(-)

diff --git a/HOWTO.rst b/HOWTO.rst
index 0978879c..a5fa432e 100644
--- a/HOWTO.rst
+++ b/HOWTO.rst
@@ -4391,33 +4391,60 @@ The `filename` is given as an absolute path. The `action` can be one of these:
 The file I/O action format::
 
     filename action offset length
 
 The `filename` is given as an absolute path, and has to have been added and
 opened before it can be used with this format. The `offset` and `length` are
 given in bytes. The `action` can be one of these:
 
 **wait**
 	   Wait for `offset` microseconds. Everything below 100 is discarded.
-	   The time is relative to the previous `wait` statement.
+	   The time is relative to the previous `wait` statement. Note that
+	   action `wait` is not allowed as of version 3, as the same behavior
+	   can be achieved using timestamps.
 **read**
 	   Read `length` bytes beginning from `offset`.
 **write**
 	   Write `length` bytes beginning from `offset`.
 **sync**
 	   :manpage:`fsync(2)` the file.
 **datasync**
 	   :manpage:`fdatasync(2)` the file.
 **trim**
 	   Trim the given file from the given `offset` for `length` bytes.
 
 
+Trace file format v3
+~~~~~~~~~~~~~~~~~~~~
+
+The third version of the trace file format was added in fio version 3.31. It
+forces each action to have a timestamp associated with it.
+
+The first line of the trace file has to be::
+
+    fio version 3 iolog
+
+Following this can be lines in two different formats, which are described below.
+
+The file management format::
+
+    timestamp filename action
+
+The file I/O action format::
+
+    timestamp filename action offset length
+
+The `timestamp` is relative to the beginning of the run (ie starts at 0). The
+`filename`, `action`, `offset` and `length`  are identical to version 2, except
+that version 3 does not allow the `wait` action.
+
+
 I/O Replay - Merging Traces
 ---------------------------
 
 Colocation is a common practice used to get the most out of a machine.
 Knowing which workloads play nicely with each other and which ones don't is
 a much harder task. While fio can replay workloads concurrently via multiple
 jobs, it leaves some variability up to the scheduler making results harder to
 reproduce. Merging is a way to make the order of events consistent.
 
 Merging is integrated into I/O replay and done when a
diff --git a/fio.1 b/fio.1
index 98410655..a2ec836f 100644
--- a/fio.1
+++ b/fio.1
@@ -4110,38 +4110,71 @@ The file I/O action format:
 .RS
 filename action offset length
 .P
 The `filename' is given as an absolute path, and has to have been \fBadd\fRed and
 \fBopen\fRed before it can be used with this format. The `offset' and `length' are
 given in bytes. The `action' can be one of these:
 .RS
 .TP
 .B wait
 Wait for `offset' microseconds. Everything below 100 is discarded.
-The time is relative to the previous `wait' statement.
+The time is relative to the previous `wait' statement. Note that action `wait`
+is not allowed as of version 3, as the same behavior can be achieved using
+timestamps.
 .TP
 .B read
 Read `length' bytes beginning from `offset'.
 .TP
 .B write
 Write `length' bytes beginning from `offset'.
 .TP
 .B sync
 \fBfsync\fR\|(2) the file.
 .TP
 .B datasync
 \fBfdatasync\fR\|(2) the file.
 .TP
 .B trim
 Trim the given file from the given `offset' for `length' bytes.
 .RE
 .RE
+.RE
+.TP
+.B Trace file format v3
+The third version of the trace file format was added in fio version 3.31. It
+forces each action to have a timestamp associated with it.
+.RS
+.P
+The first line of the trace file has to be:
+.RS
+.P
+"fio version 3 iolog"
+.RE
+.P
+Following this can be lines in two different formats, which are described below.
+.P
+.B
+The file management format:
+.RS
+timestamp filename action
+.P
+.RE
+.B
+The file I/O action format:
+.RS
+timestamp filename action offset length
+.P
+The `timestamp` is relative to the beginning of the run (ie starts at 0). The
+`filename`, `action`, `offset` and `length`  are identical to version 2, except
+that version 3 does not allow the `wait` action.
+.RE
+.RE
 .SH I/O REPLAY \- MERGING TRACES
 Colocation is a common practice used to get the most out of a machine.
 Knowing which workloads play nicely with each other and which ones don't is
 a much harder task. While fio can replay workloads concurrently via multiple
 jobs, it leaves some variability up to the scheduler making results harder to
 reproduce. Merging is a way to make the order of events consistent.
 .P
 Merging is integrated into I/O replay and done when a \fBmerge_blktrace_file\fR
 is specified. The list of files passed to \fBread_iolog\fR go through the merge
 process and output a single file stored to the specified file. The output file is
-- 
2.30.2