proc.5: Small fixes to Peter Schiffer's /proc/PID/io patch

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

man5/proc.5

@@ -59,7 +59,7 @@
 .\" to see what information could be imported from that file
 .\" into this file.
 .\"
-.TH PROC 5 2013-06-27 "Linux" "Linux Programmer's Manual"
+.TH PROC 5 2013-08-01 "Linux" "Linux Programmer's Manual"
 .SH NAME
 proc \- process information pseudo-file system
 .SH DESCRIPTION
@@ -352,7 +352,8 @@ file access mode and file status flags (see
 The files in this directory are readable only by the owner of the process.
 .TP
 .IR /proc/[pid]/io " (since kernel 2.6.20)"
-This file contains IO statistics for each running process, for example:
+.\" commit 7c3ab7381e79dfc7db14a67c6f4f3285664e1ec2
+This file contains I/O statistics for the process, for example:
 .in +4n
 .nf
 
@@ -369,75 +370,66 @@ cancelled_write_bytes: 0
 
 The fields are as follows:
 .RS
-.IP * 2
+.TP
-.IR rchar :
+.IR rchar ": characters read"
-chars read
-
 The number of bytes which this task has caused to be read from storage.
 This is simply the sum of bytes which this process passed to
 .BR read (2)
-and
+and similar system calls.
-.BR pread (2).
+It includes things such as terminal I/O and 
-It includes things like tty IO and it is unaffected by whether or not actual
+is unaffected by whether or not actual
-physical disk IO was required (the read might have been satisfied from
+physical disk I/O was required (the read might have been satisfied from
 pagecache).
-.IP *
+.TP
-.IR wchar :
+.IR wchar ": characters written"
-chars written
-
 The number of bytes which this task has caused, or shall cause to be written
 to disk.
 Similar caveats apply here as with
 .IR rchar .
-.IP *
+.TP
-.IR syscr :
+.IR syscr ": read syscalls"
-read syscalls
+Attempt to count the number of read I/O operations\(emthat is,
-
+system calls such as
-Attempt to count the number of read I/O operations, i.e. syscalls like
 .BR read (2)
 and
 .BR pread (2).
-.IP *
+.TP
-.IR syscw :
+.IR syscw ": write syscalls"
-write syscalls
+Attempt to count the number of write I/O operations\(emthat is,
-
+system calls such as
-Attempt to count the number of write I/O operations, i.e. syscalls like
 .BR write (2)
 and
 .BR pwrite (2).
-.IP *
+.TP
-.IR read_bytes :
+.IR read_bytes ": bytes read"
-bytes read
-
 Attempt to count the number of bytes which this process really did cause to
 be fetched from the storage layer.
 This is accurate for block-backed filesystems.
-.IP *
+.TP
-.IR write_bytes :
+.IR write_bytes ": bytes written"
-bytes written
-
 Attempt to count the number of bytes which this process caused to be sent to
 the storage layer.
-.IP *
+.TP
 .IR cancelled_write_bytes :
-
 The big inaccuracy here is truncate.
 If a process writes 1MB to a file and then deletes the file,
 it will in fact perform no writeout.
 But it will have been accounted as having caused 1MB of write.
-In other words: this field represents number of bytes which this process
+In other words: this field represents the number of bytes which this process
 caused to not happen, by truncating pagecache.
-A task can cause "negative" IO too.
+A task can cause "negative" I/O too.
 If this task truncates some dirty pagecache,
-some IO which another task has been accounted for
+some I/O which another task has been accounted for
-(in its write_bytes) will not be happening.
+(in its
+.IR write_bytes )
+will not be happening.
+.RE
 .IP
 .IR Note :
-
+In the current implementation, things are a bit racy on 32-bit systems:
-At its current implementation state, this is a bit racy on 32-bit systems:
 if process A reads process B's
 .I /proc/[pid]/io
-while process B is updating one of those 64-bit counters,
+while process B is updating one of these 64-bit counters,
 process A could see an intermediate result.
 .RE
 .TP