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NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXIT STATUS | ENVIRONMENT | FILES | EXAMPLES | RESOURCES | COPYRIGHT | THANKS | SEE ALSO | COLOPHON |
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LTTNG-RECLAIM-MEMO(1) LTTng Manual LTTNG-RECLAIM-MEMO(1)
lttng-reclaim-memory - Reclaim channel memory immediately
lttng [GENERAL OPTIONS] reclaim-memory --userspace
[--no-wait] [--older-than=AGEUS]
[--session=SESSION] (--all | CHANNEL...)
The lttng reclaim-memory command immediately reclaims memory for
the sub-buffers of:
With the --all option
All the user space channels of the targeted session.
With one or more CHANNEL arguments
Each named user space channel.
The targeted session is either:
With the --session=SESSION argument
The recording session named SESSION.
Otherwise
The current recording session (see lttng-concepts(7) to learn
more about the current recording session).
See lttng-concepts(7) to learn more about channel memory reclaim.
The channel memory reclaim operation behaviour depends on the
configured event record loss mode of the channel:
Discard mode
Only reclaim sub-buffers that have been both delivered
(completed and ready to be consumed) and consumed, since
unconsumed data would be lost forever.
Overwrite mode
Reclaim any delivered sub-buffer, since old data will be
overwritten anyway: no need to wait for consumption.
Specify a sub-buffer age threshold with the --older-than=AGEUS
option: only sub-buffers of which the age of the closing time is
older than AGEUS µs are eligible for a memory reclaim. Moreover:
If AGEUS > last stream activity age
The sub-buffers of which the age, at the moment of closing
them, is greater than AGEUS µs are eligible for a memory
reclaim.
If AGEUS < last stream activity age
All the sub-buffers are eligible.
The LTTng tracers flush for the targeted channel so that any
open sub-buffer gets closed to become eligible.
By default, the command waits for the memory reclaim operation to
complete and displays the number of reclaimed sub-buffers. Use the
--no-wait option to exit immediately without waiting for
completion.
See the “EXAMPLES” section below for usage examples.
See lttng(1) for GENERAL OPTIONS.
Program information
-h, --help
Show help.
This option attempts to launch /usr/bin/man to view this
manual page. Override the manual pager path with the
LTTNG_MAN_BIN_PATH environment variable.
--list-options
List available command options and quit.
-a, --all
Reclaim memory for all the user space channels of the targeted
session.
--older-than=AGEUS
Only reclaim sub-buffers of which the age (µs) of the closing
time is greater than AGEUS µs instead of reclaiming the memory
of all eligible sub-buffers.
The ms (milliseconds), s (seconds), m (minutes), and h (hours)
suffixes are supported.
--no-wait
Do NOT wait for the memory reclaim operation to complete
before exiting.
-s SESSION, --session=SESSION
Reclaim memory for channels of the recording session named
SESSION.
-u, --userspace
Reclaim memory of a user space channel.
As of LTTng 2.15.1, this option is mandatory.
0
Success
1
Command error
2
Undefined command
3
Fatal error
4
Command warning (something went wrong during the command)
LTTNG_ABORT_ON_ERROR
Set to 1 to abort the process after the first error is
encountered.
LTTNG_HOME
Path to the LTTng home directory.
Defaults to $HOME.
Useful when the Unix user running the commands has a
non-writable home directory.
LTTNG_LIST_LEGACY
Set to 1 to use the legacy output format (LTTng 2.14 and
earlier) for the lttng-list(1) command instead of the modern
output format.
Note that the legacy output doesn’t show anything related to
features introduced after LTTng 2.14.
LTTNG_MAN_BIN_PATH
Absolute path to the manual pager to use to read the LTTng
command-line help (with lttng-help(1) or with the --help
option) instead of /usr/bin/man.
LTTNG_NO_UTF_8
Set to 1 to NOT emit multi-byte UTF-8 sequences, even if the
locale claims to support it.
LTTNG_SESSION_CONFIG_XSD_PATH
Path to the directory containing the session.xsd recording
session configuration XML schema.
LTTNG_SESSIOND_PATH
Absolute path to the LTTng session daemon binary (see
lttng-sessiond(8)) to spawn from the lttng-create(1) command.
The --sessiond-path general option overrides this environment
variable.
LTTNG_TERM_COLOR
Controls when to emit terminal SGR codes in the output.
The NO_COLOR environment variable overrides this.
One of:
auto (default)
Only emit SGR codes when the standard output is connected
to a color-capable terminal.
always
Always emit SGR codes.
never
Never emit SGR codes.
NO_COLOR
If set and not empty, then it’s equivalent to setting
LTTNG_TERM_COLOR to never.
See NO_COLOR <https://no-color.org/> to learn more.
$LTTNG_HOME/.lttngrc
Unix user’s LTTng runtime configuration.
This is where LTTng stores the name of the Unix user’s current
recording session between executions of lttng(1).
lttng-create(1) and lttng-set-session(1) set the current
recording session.
$LTTNG_HOME/lttng-traces
Default output directory of LTTng traces in local and snapshot
modes.
Override this path with the --output option of the
lttng-create(1) command.
$LTTNG_HOME/.lttng
Unix user’s LTTng runtime and configuration directory.
$LTTNG_HOME/.lttng/sessions
Default directory containing the Unix user’s saved recording
session configurations (see lttng-save(1) and lttng-load(1)).
/usr/local/etc/lttng/sessions
Directory containing the system-wide saved recording session
configurations (see lttng-save(1) and lttng-load(1)).
Note
$LTTNG_HOME defaults to the value of the HOME environment
variable.
Example 1. Reclaim memory for all eligible sub-buffers of user
space channel my-channel (current recording session).
$ lttng reclaim-memory --userspace my-channel
Example 2. Reclaim memory for sub-buffers older than 2 s of user
space channels mon-canal and mein-Kanal (current recording
session).
$ lttng reclaim-memory --userspace --older-than=2s \
mon-canal mein-Kanal
Example 3. Reclaim memory for all user space channels of the
recording session named my-session without waiting for completion.
$ lttng reclaim-memory --userspace --session=my-session \
--no-wait --all
• LTTng project website <https://lttng.org>
• LTTng documentation <https://lttng.org/docs>
• LTTng bug tracker <https://bugs.lttng.org>
• Git repositories <https://git.lttng.org>
• GitHub organization <https://github.com/lttng>
• Continuous integration <https://ci.lttng.org/>
• Mailing list <https://lists.lttng.org/> for support and
development: lttng-dev@lists.lttng.org
• IRC channel <irc://irc.oftc.net/lttng>: #lttng on irc.oftc.net
• Mastodon <https://mastodon.social/@lttng>
This program is part of the LTTng-tools project.
LTTng-tools is distributed under the GNU General Public License
version 2 <http://www.gnu.org/licenses/old-
licenses/gpl-2.0.en.html>. See the LICENSE
<https://github.com/lttng/lttng-tools/blob/master/LICENSE> file
for details.
Special thanks to Michel Dagenais and the DORSAL laboratory
<http://www.dorsal.polymtl.ca/> at École Polytechnique de Montréal
for the LTTng journey.
Also thanks to the Ericsson teams working on tracing which helped
us greatly with detailed bug reports and unusual test cases.
lttng(1), lttng-concepts(7), lttng-enable-channel(1)
This page is part of the LTTng-Tools (LTTng tools) project.
Information about the project can be found at ⟨http://lttng.org/⟩.
It is not known how to report bugs for this man page; if you know,
please send a mail to man-pages@man7.org. This page was obtained
from the project's upstream Git repository
⟨https://github.com/lttng/lttng-tools.git⟩ on 2026-08-04. (At
that time, the date of the most recent commit that was found in
the repository was 2026-07-30.) If you discover any rendering
problems in this HTML version of the page, or you believe there is
a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
man-pages@man7.org
LTTng 2.15.1 24 September 2025 LTTNG-RECLAIM-MEMO(1)
Pages that refer to this page: lttng(1), lttng-enable-channel(1), lttng-concepts(7)
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HTML rendering created 2026-09-09 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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