KERNEL PMDAS(1) KERNEL PMDAS(1)
pmdaaix, pmdadarwin, pmdafreebsd, pmdalinux, pmdanetbsd, pmdasolaris, pmdawindows - oper-
ating system kernel performance metrics domain agents
$PCP_PMDAS_DIR/aix/pmdaaix [-d domain] [-l logfile] [-U username]
$PCP_PMDAS_DIR/darwin/pmdadarwin [-d domain] [-l logfile] [-U username]
$PCP_PMDAS_DIR/freebsd/pmdafreebsd [-d domain] [-l logfile] [-U username]
$PCP_PMDAS_DIR/linux/pmdalinux [-d domain] [-l logfile] [-U username]
$PCP_PMDAS_DIR/netbsd/pmdanetbsd [-d domain] [-l logfile] [-U username]
$PCP_PMDAS_DIR/solaris/pmdasolaris [-d domain] [-l logfile] [-U username]
$PCP_PMDAS_DIR/windows/pmdawindows [-d domain] [-l logfile] [-U username]
Each supported platform has a kernel Performance Metrics Domain Agent (PMDA) which
extracts performance metrics from the kernel of that platfrom. A variety of platform-spe-
cific metrics are available, with an equally varied set of access mechanisms - typically
this involves special system calls, or reading from files in kernel virtual filesystems
such as the Linux sysfs and procfs filesystems.
The platform kernel PMDA is one of the most critical components of the PCP installation,
and must be as efficient and reliable as possible. In all installations the default ker-
nel PMDA will be installed as a shared library and thus executes directly within the
pmcd(1) process. This slightly reduces overheads associated with querying the metadata
and values associated with these metrics (no message passing is required).
Unlike many other PMDAs, the kernel PMDA exports a number of metric namespace subtrees,
such as kernel, network, swap, mem, ipc, filesys, nfs, disk and hinv (hardware inventory).
Despite usually running as shared libraries, most installations also include a stand-alone
executable for the kernel PMDA. This is to aid profiling and debugging activities, with
dbpmda(1) for example. In this case (but not for shared libraries), the following command
line options are available:
-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 [platform].log is written in
the current directory of pmcd(1) when pmda[platform] 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.
-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.
Access to the names, help text and values for the kernel performance metrics is available
by default - unlike most other agents, no action is required to enable them and they
should not be removed.
default help text file for the the kernel metrics
default log file for error messages and other information from the kernel PMDA.
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), dbpmda(1) pmcd(1), pcp.conf(5) and pcp.env(5).
Performance Co-Pilot PCP KERNEL PMDAS(1)