mirror of
git://sourceware.org/git/lvm2.git
synced 2025-11-30 04:23:48 +03:00
d9063048cb
Add thread reuse mechanism to reduce overhead when devices are frequently registered/unregistered by introducing a configurable grace period where monitoring threads wait for potential reuse before termination. Key changes: - Add -g option to configure grace period (0-300 seconds, default: 10s) - Introduce DM_THREAD_GRACE_PERIOD state for threads awaiting reuse - Implement thread reuse for matching device/dso combinations - Add pthread condition variables and mutexes for grace period synchronization - Add thread usage counter and enhanced debug logging - Add _reset_pending_signal() to handle SIGALRM cleanup on thread reuse - Refactor _monitor_thread() to support grace period workflow - Update timeout thread to skip non-running threads - Simplify thin plugin logging This optimization significantly reduces thread creation/destruction overhead in scenarios with rapid device registration/unregistration cycles, such as creating snapshots of thin volumes, while maintaining proper cleanup and thread safety.
233 lines
6.4 KiB
Plaintext
233 lines
6.4 KiB
Plaintext
.TH DMEVENTD 8 "DM TOOLS #VERSION#" "Red Hat, Inc." \" -*- nroff -*-
|
|
.
|
|
.de NSY
|
|
. ie t .SY \\$1
|
|
. el \{\
|
|
. ie \\n(.$>1 \{\
|
|
. PD 0
|
|
. TP \\w'\\$1\ 'u
|
|
. \}
|
|
. el .TP
|
|
. B \\$1
|
|
. nh
|
|
. na
|
|
. \}
|
|
..
|
|
.
|
|
.SH NAME
|
|
.
|
|
dmeventd \(em Device-mapper event daemon
|
|
.
|
|
.SH SYNOPSIS
|
|
.
|
|
.NSY dmeventd 1
|
|
.RB [ -d
|
|
.RB [ -d
|
|
.RB [ -d ]]]
|
|
.RB [ -e\ \c
|
|
.IR exit_on_path ]
|
|
.RB [ -f ]
|
|
.RB [ -g\ \c
|
|
.IR seconds ]
|
|
.RB [ -h ]
|
|
.RB [ -i ]
|
|
.RB [ -l ]
|
|
.RB [ -R ]
|
|
.RB [ -V ]
|
|
.RB [ -? ]
|
|
.
|
|
.PD
|
|
.ad
|
|
.hy
|
|
.
|
|
.SH DESCRIPTION
|
|
.
|
|
dmeventd is the event monitoring daemon for device-mapper devices.
|
|
Library plugins can register and carry out actions triggered when
|
|
particular events occur.
|
|
.
|
|
.SH OPTIONS
|
|
.
|
|
.TP
|
|
.B -d
|
|
Repeat from 1 to 3 times
|
|
.RB ( -d ,
|
|
.BR -dd ,
|
|
.BR -ddd )
|
|
to increase the detail of
|
|
debug messages sent to syslog.
|
|
Each extra d adds more debugging information.
|
|
.
|
|
.TP
|
|
\fB-e\fP \fIexit_on_path\fP
|
|
Specifies the file path whose presence is checked by the daemon when it
|
|
receives a signal (SIGINT, SIGTERM) and allows it to exit even
|
|
if there are still monitored devices.
|
|
This can help with system shutdown where devices
|
|
have not been unmonitored properly.
|
|
To disable this behavior set this to the empty string "".
|
|
Default value is "\fI#DEFAULT_DMEVENTD_EXIT_ON_PATH#\fP".
|
|
.
|
|
.TP
|
|
.B -f
|
|
Don't fork, run in the foreground.
|
|
.
|
|
.TP
|
|
\fB-g\fP \fIseconds\fP
|
|
Set the grace period for monitoring thread cleanup (0-300 seconds, default: 10).
|
|
During this period, monitoring threads that have finished processing events
|
|
will wait for potential reuse rather than immediately terminating.
|
|
If the same device and plugin combination is registered again within
|
|
the grace period, the existing thread is reused, significantly reducing
|
|
overhead. Set to 0 to disable thread reuse.
|
|
.
|
|
.TP
|
|
.B -h
|
|
Show help information.
|
|
.
|
|
.TP
|
|
.B -i
|
|
Query the running daemon instance for the status information. The format is
|
|
internal and unstable and it is targeted for developers.
|
|
Format may change between versions.
|
|
.
|
|
.TP
|
|
.B -l
|
|
Log through stdout and stderr instead of syslog.
|
|
This option works only with option -f, otherwise it is ignored.
|
|
.
|
|
.TP
|
|
.B -?
|
|
Show help information on stderr.
|
|
.
|
|
.TP
|
|
.B -R
|
|
Replace a running dmeventd instance. The running dmeventd must be version
|
|
2.02.77 or newer. The new dmeventd instance will obtain a list of devices and
|
|
events to monitor from the currently running daemon.
|
|
.
|
|
.TP
|
|
.B -V
|
|
Show version of dmeventd.
|
|
.
|
|
.SH LVM PLUGINS
|
|
.
|
|
.TP
|
|
.B Mirror
|
|
Attempts to handle device failure automatically.
|
|
See
|
|
.BR lvm.conf (5).
|
|
.
|
|
.TP
|
|
.B Raid
|
|
Attempts to handle device failure automatically.
|
|
See
|
|
.BR lvm.conf (5).
|
|
.
|
|
.TP
|
|
.B Snapshot
|
|
Monitors how full a snapshot is becoming and emits a warning to
|
|
syslog when it exceeds 80% full.
|
|
The warning is repeated when 85%, 90% and 95% of the snapshot is filled.
|
|
See
|
|
.BR lvm.conf (5).
|
|
Snapshot which runs out of space gets invalid and when it is mounted,
|
|
it gets umounted if possible.
|
|
.
|
|
.TP
|
|
.B Thin
|
|
Monitors how full thin pool data and metadata are becoming and emits
|
|
a warning to syslog when it exceeds 80% full.
|
|
The warning is repeated when more than 85%, 90% and 95%
|
|
of the thin pool is filled. See
|
|
.BR lvm.conf (5).
|
|
When a thin pool fills over 50% (data or metadata) thin plugin calls
|
|
configured \fBdmeventd/\:thin_command\fP with every 5% increase.
|
|
With default setting it calls internal
|
|
\fBlvm lvextend --use-policies\fP to resize thin pool
|
|
when it's been filled above configured threshold
|
|
\fBactivation/\:thin_pool\%_auto\%extend\%_threshold\fP.
|
|
If the command fails, dmeventd thin plugin will keep
|
|
retrying execution with increasing time delay between
|
|
retries up to 42 minutes.
|
|
User may also configure external command to support more advanced
|
|
maintenance operations of a thin pool.
|
|
Such external command can e.g. remove some unneeded snapshots,
|
|
use \fBfstrim\fP(8) to recover free space in a thin pool,
|
|
but also can use \fBlvextend --use-policies\fP if other actions
|
|
have not released enough space.
|
|
Command is executed with environment variable
|
|
\fBLVM_RUN_BY\%_DM\%EVENTD=1\fP
|
|
so any lvm2 command executed in this environment
|
|
will not try to interact with dmeventd.
|
|
To see the fullness of a thin pool command
|
|
may check these two environment variables
|
|
\fBDMEVENTD\%_THIN\%_POOL\%_DATA\fP and
|
|
\fBDMEVENTD\%_THIN\%_POOL\%_METADATA\fP.
|
|
Command can also read status with tools like \fBlvs\fP(8).
|
|
.
|
|
.TP
|
|
.B Vdo
|
|
Monitors how full a VDO pool data is becoming and emits
|
|
a warning to syslog when it exceeds 80% full.
|
|
The warning is repeated when more than 85%, 90% and 95%
|
|
of the VDO pool is filled. See
|
|
.BR lvm.conf (5).
|
|
When a VDO pool fills over 50% vdo plugin calls
|
|
configured \fBdmeventd/\:vdo_command\fP with every 5% increase.
|
|
With default setting it calls internal
|
|
\fBlvm lvextend --use-policies\fP to resize VDO pool
|
|
when it's been filled above the configured threshold
|
|
\fBactivation/\:vdo_pool\%_auto\%extend\%_threshold\fP.
|
|
If the command fails, dmeventd vdo plugin will keep
|
|
retrying execution with increasing time delay between
|
|
retries up to 42 minutes.
|
|
User may also configure external command to support more advanced
|
|
maintenance operations of a VDO pool.
|
|
Such external command can e.g. remove some unneeded space
|
|
with \fBfstrim\fP(8),
|
|
but also can use \fBlvextend --use-policies\fP
|
|
if other actions have not released enough space.
|
|
Command is executed with environment variable
|
|
\fBLVM_RUN_BY\%_DMEVENTD=1\fP so any lvm2 command executed
|
|
in this environment will not try to interact with dmeventd.
|
|
To see the fullness of a VDO pool command may check this
|
|
environment variable \fBDMEVENTD_VDO_POOL\fP.
|
|
Command can also read status with tools like \fBlvs\fP(8).
|
|
.
|
|
.SH ENVIRONMENT VARIABLES
|
|
.
|
|
.TP
|
|
.B DMEVENTD_THIN_POOL_DATA
|
|
Variable is set by thin plugin and is available to executed program.
|
|
Value represents actual usage of thin pool data volume.
|
|
Variable is not set when error event is processed.
|
|
.
|
|
.TP
|
|
.B DMEVENTD_THIN_POOL_METADATA
|
|
Variable is set by thin plugin and is available to executed program.
|
|
Value represents actual usage of thin pool metadata volume.
|
|
Variable is not set when error event is processed.
|
|
.
|
|
.TP
|
|
.B DMEVENTD_VDO_POOL
|
|
Variable is set by vdo plugin and is available to executed program.
|
|
Value presents actual usage of VDO pool data volume.
|
|
Variable is not set when error event is processed.
|
|
.
|
|
.TP
|
|
.B LVM_RUN_BY_DMEVENTD
|
|
Variable is set by thin and vdo plugin to prohibit recursive interaction
|
|
with dmeventd by any executed lvm2 command from
|
|
a thin_command, vdo_command environment.
|
|
.
|
|
.SH SEE ALSO
|
|
.
|
|
.nh
|
|
.na
|
|
.BR lvm (8),
|
|
.BR lvm.conf (5),
|
|
.BR lvextend (8),
|
|
.P
|
|
.BR fstrim (8)
|