NAME¶
pmdajbd2 - journal block device (JBD) performance metrics domain agent
(PMDA)
SYNOPSIS¶
$PCP_PMDAS_DIR/jbd2/pmdajbd2 [
-d domain] [
-l
logfile] [
-j path] [
-U username]
DESCRIPTION¶
pmdajbd2 is a Performance Metrics Domain Agent (PMDA) which extracts
performance metrics from the Journal Block Device subsystem (version 2) in the
Linux kernel. These metrics are exported by the kernel in procfs files, one
file per block device. The JBD2 subsystem is used by several filesystems
including ext3, ext4 and ocfs2.
The
jbd2 PMDA exports metrics that measure detailed journal transaction
information, such as time spent waiting and locked, request rates, blocks used
and so on.
A brief description of the
pmdajbd2 command line options follows (these
are only relevant when running the PMDA as a daemon, and not as a shared
library):
- -d
- It is absolutely crucial that the performance metrics domain number
specified here is unique and consistent. That is, domain should be
different for every PMDA on the one host, and the same domain
number should be used for the same PMDA on all hosts.
- -l
- Location of the log file. By default, when running as a daemon a log file
named jbd2.log is written in the current directory of when
pmdajbd2 is started, i.e. $PCP_LOG_DIR/pmcd. If the log file
cannot be created or is not writable, output is written to the standard
error instead. When running in shared library mode, and diagnostic
information will be written into the pmcd log file, namely
$PCP_LOG_DIR/pmcd/pmcd.log.
- -j
- Allows an alternate path to the jbd2 statistics files to be specified. The
default path is /proc/fs/jbd2.
- -U
- User account under which to run the agent. The default is the unprivileged
"pcp" account in current versions of PCP, but in older versions
the superuser account ("root") was used by default.
INSTALLATION¶
This PMDA is installed by default and in the shared library mode (rather than as
a separate daemon to
pmcd(1)). Thus, the names, help text and values
for the jbd2 performance metrics should always be available.
If you do not use these metrics you can remove this PMDA, do the following as
root:
# cd $PCP_PMDAS_DIR/jbd2
# ./Remove
If you want to enable the installation again, do the following as root:
# cd $PCP_PMDAS_DIR/jbd2
# ./Install
pmdajbd2 is launched by
pmcd(1) and should never be executed
directly. The Install and Remove scripts notify
pmcd(1) when the agent
is installed or removed.
FILES¶
- $PCP_PMCDCONF_PATH
- command line options used to launch pmdajbd2
- $PCP_PMDAS_DIR/jbd2/help
- default help text file for the jbd2 metrics
- $PCP_PMDAS_DIR/jbd2/Install
- installation script for the pmdajbd2 agent
- $PCP_PMDAS_DIR/jbd2/Remove
- undo installation script for the pmdajbd2 agent
- $PCP_LOG_DIR/pmcd/jbd2.log
- default log file for error messages and other information from
pmdajbd2
PCP ENVIRONMENT¶
Environment variables with the prefix
PCP_ are used to parameterize the
file and directory names used by PCP. On each installation, the file
/etc/pcp.conf contains the local values for these variables. The
$PCP_CONF variable may be used to specify an alternative configuration
file, as described in
pcp.conf(5).
SEE ALSO¶
PCPIntro(1),
pmcd(1),
pcp.conf(5) and
pcp.env(5).