A.5. Metric Configuration (using pmstore)

Some metrics in PCP allow the modification of their values, especially in the case where the metric acts as a control variable. This is the case with the gsf2.control.* metrics with the GFS2 PMDA. This is achieved through the use of the pmstore command line tool. As with most of the other PCP tools, the pmstore tool normally changes the current value for the specified metric on the local system, but you can use the -h switch to allow the change of metric values on specified remote systems. For further information, see the pmstore(3) man page.
As an example, the following command enables all of the GSF2 tracepoints on the local machine on a system with the GFS2 PMDA installed and loaded. When this command is run, the PMDA will switch on all of the GFS2 tracepoints in the debugfs file system.
# pmstore gfs2.control.tracepoints.all 1
gfs2.control.tracepoints.all old value=0 new value=1
Table A.3, “Control Tracepoints” describes each of the control tracepoints and its usage. An explanation on the effect of each control tracepoint and its available options is available through the help switch in the pminfo tool.

Table A.3. Control Tracepoints

Control MetricUse and Available Options
gfs2.contol.tracepoints.all The GFS2 tracepoint statistics can be manually controlled using 0 [off] or 1 [on]. Setting the value of the metric controls the behavior of the PMDA to whether it tries to collect from tracepoint metrics or not.
gfs2.control.tracepoints.* The GFS2 tracepoint statistics can be manually controlled using 0 [off] or 1 [on]. Setting the value of the metric controls the behavior of the PMDA to whether it tries to collect from each specified tracepoint metric or not.
gfs2.control.global_tracing The global tracing can be controlled using 0 [off] or 1 [on]. This is required to be on for most of the GFS2 metrics to function.
gfs2.control.worst_glock Can be individually controlled whether on or off using the control metrics.0 [off] or 1 [on]. Setting the value of the metric controls the behavior of the PMDA to whether it tries to collect the lock_time metrics or not. The machine must have the GFS2 tracepoints available for the glock_lock_time based metrics to function.
gfs2.control.latency The gfs2.latency statistics can be manually controlled using pmstore gfs2.control.latency 0 [off] or 1 [on]. Setting the value of the metric controls the behavior of the PMDA to whether it tries to collect the latency metrics or not. The machine must have the gfs2 tracepoints available for the latency metrics to function.
gfs2.control.glock_threshold The number of glocks that will be processed and accepted over all ftrace statistics. This number can be manually altered using the pmstore tool in order to tailor the number of glocks processed. This value must be positive.