1PMDAJBD2(1) General Commands Manual PMDAJBD2(1)
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6 pmdajbd2 - journal block device (JBD) performance metrics domain agent
7 (PMDA)
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10 $PCP_PMDAS_DIR/jbd2/pmdajbd2 [-d domain] [-l logfile] [-j path] [-U
11 username]
12
14 pmdajbd2 is a Performance Metrics Domain Agent (PMDA) which extracts
15 performance metrics from the Journal Block Device subsystem (version 2)
16 in the Linux kernel. These metrics are exported by the kernel in
17 procfs files, one file per block device. The JBD2 subsystem is used by
18 several filesystems including ext3, ext4 and ocfs2.
19 The jbd2 PMDA exports metrics that measure detailed journal transaction
21 information, such as time spent waiting and locked, request rates,
22 blocks used and so on.
23 A brief description of the pmdajbd2 command line options follows (these
25 are only relevant when running the PMDA as a daemon, and not as a
26 shared library):
27 -d It is absolutely crucial that the performance metrics domain num‐
29 ber specified here is unique and consistent. That is, domain
30 should be different for every PMDA on the one host, and the same
31 domain number should be used for the same PMDA on all hosts.
32 -l Location of the log file. By default, when running as a daemon a
34 log file named jbd2.log is written in the current directory of
35 when pmdajbd2 is started, i.e. $PCP_LOG_DIR/pmcd. If the log
36 file cannot be created or is not writable, output is written to
37 the standard error instead. When running in shared library mode,
38 and diagnostic information will be written into the pmcd log file,
39 namely $PCP_LOG_DIR/pmcd/pmcd.log.
40 -j Allows an alternate path to the jbd2 statistics files to be speci‐
42 fied. The default path is /proc/fs/jbd2.
43 -U User account under which to run the agent. The default is the un‐
45 privileged "pcp" account in current versions of PCP, but in older
46 versions the superuser account ("root") was used by default.
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49 This PMDA is installed by default and in the shared library mode
50 (rather than as a separate daemon to pmcd(1)). Thus, the names, help
51 text and values for the jbd2 performance metrics should always be
52 available.
53 If you do not use these metrics you can remove this PMDA, do the fol‐
55 lowing as root:
56 # cd $PCP_PMDAS_DIR/jbd2
58 # ./Remove
59 If you want to enable the installation again, do the following as root:
61 # cd $PCP_PMDAS_DIR/jbd2
63 # ./Install
64 pmdajbd2 is launched by pmcd(1) and should never be executed directly.
66 The Install and Remove scripts notify pmcd(1) when the agent is in‐
67 stalled or removed.
68
70 $PCP_PMCDCONF_PATH
71 command line options used to launch pmdajbd2
72 $PCP_PMDAS_DIR/jbd2/help
73 default help text file for the jbd2 metrics
74 $PCP_PMDAS_DIR/jbd2/Install
75 installation script for the pmdajbd2 agent
76 $PCP_PMDAS_DIR/jbd2/Remove
77 undo installation script for the pmdajbd2 agent
78 $PCP_LOG_DIR/pmcd/jbd2.log
79 default log file for error messages and other information
80 from pmdajbd2
81
83 Environment variables with the prefix PCP_ are used to parameterize the
84 file and directory names used by PCP. On each installation, the file
85 /etc/pcp.conf contains the local values for these variables. The
86 $PCP_CONF variable may be used to specify an alternative configuration
87 file, as described in pcp.conf(5).
88
90 PCPIntro(1), pmcd(1), pcp.conf(5) and pcp.env(5).
91Performance Co-Pilot PCP PMDAJBD2(1)