.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"
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.
If no \fB\-o, \-\-output\fP is specified, the traces will be written in
$HOME/lttng-traces.
+
+The $HOME environment variable can be overridden by defining the environment
+variable LTTNG_HOME. This is useful when the user running the commands has
+a non-writeable home directory.
.fi
.B OPTIONS:
file.
It is important to note that if a certain type of buffers is used, the session
-will be set with that type and all other subsequent channel need to have the
+will be set with that type and all other subsequent channel needs to have the
same type.
+
+Note that once the session has been started and enabled on the tracer side,
+it's not possible anymore to enable a new channel for that session.
.fi
.B OPTIONS:
\-\-overwrite
Flight recorder mode : overwrites events when subbuffers are full
\-\-subbuf-size SIZE
- Subbuffer size in bytes (default: 4096, kernel default: 262144)
- Needs to be a power of 2 for both tracers
+ Subbuffer size in bytes {+k,+M,+G}
+ (default UST uid: 131072, UST pid: 4096, kernel: 262144, metadata: 4096)
+ Rounded up to the next power of 2.
+
+ The minimum subbuffer size, for each tracer, is the max value between
+ the default above and the system page size. You can issue this command
+ to get the current page size on your system: \fB$ getconf PAGE_SIZE\fP
\-\-num-subbuf NUM
- Number of subbuffers (default: 4)
- Needs to be a power of 2 for both tracers
+ Number of subbuffers. (default UST uid: 4, UST pid: 4, kernel: 4, metadata: 2)
+ Rounded up to the next power of 2.
\-\-switch-timer USEC
- Switch subbuffer timer interval in µsec (default: 0)
+ Switch subbuffer timer interval in µsec.
+ (default UST uid: 0, UST pid: 0, kernel: 0, metadata: 0)
\-\-read-timer USEC
- Read timer interval in µsec (UST default: 0, kernel default: 200000)
+ Read timer interval in µsec.
+ (default UST uid: 0, UST pid: 0, kernel: 200000, metadata: 0)
\-\-output TYPE
Channel output type. Possible values: mmap, splice
+ (default UST uid: mmap, UST pid: mmap, kernel: splice, metadata: mmap)
\-\-buffers-uid
Use per UID buffer (\-u only). Buffers are shared between applications
that have the same UID.
\-\-buffers-global
Use shared buffer for the whole system (\-k only)
\-C, \-\-tracefile-size SIZE
- Maximum size of of each tracefile within a stream (in bytes).
+ Maximum size of each tracefile within a stream (in bytes).
+ 0 means unlimited. (default: 0)
\-W, \-\-tracefile-count COUNT
Used in conjunction with \-C option, this will limit the number
- of files created to the specified count.
+ of files created to the specified count. 0 means unlimited. (default: 0)
.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.
projects / lttng-tools.git / blobdiff