A question about the snapshot: is there a way to trigger a new state dump? 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 >
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