KERNEL PMDAS(1) KERNEL PMDAS(1)NAME
pmdaaix, pmdadarwin, pmdafreebsd, pmdalinux, pmdanetbsd, pmdasolaris,
pmdawindows - operating system kernel performance metrics domain agents
SYNOPSIS
$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 user‐
name]
$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 user‐
name]
$PCP_PMDAS_DIR/windows/pmdawindows [-d domain] [-l logfile] [-U user‐
name]
DESCRIPTION
Each supported platform has a kernel Performance Metrics Domain Agent
(PMDA) which extracts performance metrics from the kernel of that plat‐
from. A variety of platform-specific metrics are available, with an
equally varied set of access mechanisms - typically this involves spe‐
cial 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 kernel 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 num‐
ber 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 [plat‐
form].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.
INSTALLATION
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.
FILES
$PCP_PMDAS_DIR/[platform]/help
default help text file for the the kernel metrics
$PCP_LOG_DIR/pmcd/pmcd.log
default log file for error messages and other information
from the kernel PMDA.
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 ALSOPCPIntro(1), dbpmda(1)pmcd(1), pcp.conf(5) and pcp.env(5).
Performance Co-Pilot PCP KERNEL PMDAS(1)
