New UST default buffers is now per UID

[lttng-tools.git] / doc / man / lttng.1

diff --git a/doc/man/lttng.1 b/doc/man/lttng.1
index afa8eb85371b40c55d2d0aa175b3976a853c985e..72454f0d3e85ad0f1c6ffeb8e4221e8251a03a07 100644 (file)
--- a/doc/man/lttng.1
+++ b/doc/man/lttng.1
@@ -1,7 +1,7 @@
 .TH "LTTNG" "1" "December 3rd, 2012" "" ""
 
 .SH "NAME"
-lttng \(em LTTng 2.1.x tracer control command line tool
+lttng \(em LTTng 2.x tracer control command line tool
 
 .SH "SYNOPSIS"
 
@@ -101,8 +101,9 @@ data output:
 Please take a look at the help (\-h/\-\-help) for a detailed list of available
 contexts.
 
-If no channel is given (\-c), the context is added to all channels. Otherwise
-the context will be added only to the given channel (\-c).
+If no channel is given (\-c), the context is added to all channels that were
+already enabled. If the session has no channel, a default channel is created.
+Otherwise the context will be added only to the given channel (\-c).
 
 If \fB\-s, \-\-session\fP is omitted, the session name is taken from the .lttngrc
 file.
@@ -214,6 +215,10 @@ automatically created having this form: 'auto-yyyymmdd-hhmmss'.
 
 If no \fB\-o, \-\-output\fP is specified, the traces will be written in
 $HOME/lttng-traces.
+
+The $HOME environment variable can be overridden by defining the environment
+variable LTTNG_HOME. This is useful when the user running the commands has
+a non-writeable home directory.
 .fi
 
 .B OPTIONS:
@@ -304,8 +309,11 @@ If \fB\-s, \-\-session\fP is omitted, the session name is taken from the .lttngr
 file.
 
 It is important to note that if a certain type of buffers is used, the session
-will be set with that type and all other subsequent channel need to have the
+will be set with that type and all other subsequent channel needs to have the
 same type.
+
+Note that once the session has been started and enabled on the tracer side,
+it's not possible anymore to enable a new channel for that session.
 .fi
 
 .B OPTIONS:
@@ -330,6 +338,10 @@ same type.
         Subbuffer size in bytes {+k,+M,+G}
         (default UST uid: 131072, UST pid: 4096, kernel: 262144, metadata: 4096)
         Rounded up to the next power of 2.
+
+        The minimum subbuffer size, for each tracer, is the max value between
+        the default above and the system page size. You can issue this command
+        to get the current page size on your system: \fB$ getconf PAGE_SIZE\fP
 \-\-num-subbuf NUM
         Number of subbuffers. (default UST uid: 4, UST pid: 4, kernel: 4, metadata: 2)
         Rounded up to the next power of 2.
@@ -359,8 +371,8 @@ same type.
 .B EXAMPLES:
 
 $ lttng enable-channel -C 4096 -W 32 chan1
-For each stream, the maximum size of a trace file will be 4096 bytes divided
-over a \fBmaximum\fP of 32 different files. The file count is appended after
+For each stream, the maximum size of each trace file will be 4096 bytes, and
+there will be a maximum of 32 different files. The file count is appended after
 the stream number as seen in the following example. The last trace file is
 smaller than 4096 since it was not completely filled.