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).