pmdammv - memory mapped values performance metrics domain agent (PMDA)
$PCP_PMDAS_DIR/mmv/pmdammv [-d domain] [-l logfile] [-U username]
pmdammv is a Performance Metrics Domain Agent (PMDA) which exports application level per-
formance metrics using memory mapped files. It offers an extremely low overhead instru-
mentation facility that is well-suited to long running, mission critical applications
where it is desirable to have performance metrics and availability information permanently
The mmv PMDA exports instrumentation that has been added to an application using the MMV
APIs (refer to mmv_stats_init(3) and mmv(5) for further details). These APIs can be
called from several languages, including C, C++, Perl, Python and Java (via the separate
``Parfait'' class library).
A brief description of the pmdammv command line options follows:
-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, a log file named mmv.log is written in the
current directory of pmcd(1) when pmdammv 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
-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.
If you want access to the names, help text and values for the mmv performance metrics, do
the following as root:
# cd $PCP_PMDAS_DIR/mmv
Note that the default mechanism for sharing memory mapped values between instrumented
applications and the mmv PMDA involves the creation of a world-writeable $PCP_TMP_DIR/mmv
directory with the sticky-bit set (similar to /tmp and /var/tmp, for example). This suf-
fices to allow any application, running under any user account, to communicate with the
PMDA (which runs under the "pcp" account by default). This may not be desirable for every
environment, and one should consider the security implications of any directory setup like
this (similar classes of issues exist as those that affect the system temporary file
The installation process will not overwrite any existing $PCP_TMP_DIR/mmv directory. Thus
it is possible to implement an alternate permissions strategy with no world-writable
directory for sharing files - any directory readable by user or group "pcp" will suffice.
If you want to undo the installation, do the following as root:
# cd $PCP_PMDAS_DIR/mmv
pmdammv 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.
command line options used to launch pmdammv
directory housing memory mapped value files
default help text file for the mmv metrics
installation script for the pmdammv agent
undo installation script for the pmdammv agent
default log file for error messages and other information from pmdammv
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 config-
uration file, as described in pcp.conf(5).
PCPIntro(1), pmcd(1), mmv_stats_init(3), mmv(5), pcp.conf(5) and pcp.env(5).
Performance Co-Pilot PCP PMDAMMV(1)