* Brosseau, Yannick ([email protected]) wrote: > A question about the snapshot: is there a way to trigger a new state dump?
Not at this point, no. > Le 2013-07-21 14:29, "Mathieu Desnoyers" <[email protected]> a > écrit : > > > Hi, > > > > I just pushed a LTTng snapshot howto (new feature of lttng 2.3-rc). I'm > > posting it to lttng-dev, since it provides a quick insight on how to use > > the snapshot feature. Comments are welcome! > > > > Thanks, > > > > Mathieu > > > > > > LTTng Flight Recorder Snapshot HOWTO > > > > Mathieu Desnoyers > > July 21st, 2013 > > > > This document presents how to use the snapshot feature of LTTng. > > > > Snapshots allow to grab the content of flight recorder tracing buffers > > at the time the snapshot record command is invoked. Flight recorder > > tracing gather trace data in memory, overwriting the oldest information, > > without requiring any disk I/O. The snapshot record command exports the > > snapshot to the destination specified by the user. > > > > Basic usage: > > > > Session daemon started as root for kernel tracing: > > > > # lttng-sessiond -d > > > > From a user part of the tracing group (for kernel tracing): > > > > $ lttng create --snapshot > > $ lttng enable-event -k -a # enable kernel tracing > > $ lttng enable-event -u -a # enable user-space tracing > > $ lttng start > > > > [ do something, generate activity on the system ] > > > > $ lttng snapshot record > > > > [ do more stuff... ] > > > > $ lttng snapshot record > > > > $ lttng stop > > $ lttng destroy > > > > Each "lttng snapshot" command records a snapshot of the current buffer > > state. "lttng enable --snapshot" automatically setups the buffers in > > overwrite mode for flight recording, and does not attach any output file > > to the trace. The "lttng snapshot record" command can be performed > > either while tracing is started or stopped. > > > > As an example, this generates the following hierarchy under the > > directory reported by the "create" command above: > > > > . > > ├── snapshot-1-20130721-141838-0 > > │ ├── kernel > > │ │ ├── channel0_0 > > │ │ ├── channel0_1 > > │ │ ├── channel0_2 > > │ │ ├── channel0_3 > > │ │ └── metadata > > │ └── ust > > │ └── uid > > │ └── 1000 > > │ └── 64-bit > > │ ├── channel0_0 > > │ ├── channel0_1 > > │ ├── channel0_2 > > │ ├── channel0_3 > > │ └── metadata > > └── snapshot-1-20130721-141842-1 > > ├── kernel > > │ ├── channel0_0 > > │ ├── channel0_1 > > │ ├── channel0_2 > > │ ├── channel0_3 > > │ └── metadata > > └── ust > > └── uid > > └── 1000 > > └── 64-bit > > ├── channel0_0 > > ├── channel0_1 > > ├── channel0_2 > > ├── channel0_3 > > └── metadata > > > > > > Then, running babeltrace on, e.g. > > > > babeltrace snapshot-1-20130721-141838-0 > > > > shows the content of the first snapshot. > > > > Please refer to the lttng(1) manpage for details on the snapshot mode. > > > > -- > > Mathieu Desnoyers > > EfficiOS Inc. > > http://www.efficios.com > > > > _______________________________________________ > > lttng-dev mailing list > > [email protected] > > http://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev > > -- Mathieu Desnoyers EfficiOS Inc. http://www.efficios.com _______________________________________________ lttng-dev mailing list [email protected] http://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev
