Hi Will,
----- Original Message -----
> [...] How, are the PCP metrics checked
> to see if they are accurate/reasonable?
It depends - various strategies exist depending on the PMDA and the nature of
the values being extracted, and the mechanisms involves. There's some examples
over in qa/{778,835,876,987,1113} ... just a small subset to give a taste.
> For estimating network utilization using PCP the network.interface.baudrate
> and network.interface.speed metrics should provide some indication of the
> interface speed. However, looking at the numbers produced by pmval below
> they don't seem to be reasonable for 1Gbps ethernet connection of em1.
There's a couple of ways interface speed is extracted - ioctl and sysfs; depends
on kernel version. The code is over in src/pmdas/linux/proc_net_dev.c - see
the
REFRESH_NET_SPEED references there. The code is dependent on the kernel/drivers
giving good values - and there's also issues like pcp commit 9b616ace2284b622 to
factor in from out of left field.
That said there could certainly be a PCP bug or two lurking here also. Best way
to step through exactly what's happening here is:
$ gdb --args /usr/bin/pminfo -L -K clear -K
add,60,`pwd`/src/pmdas/linux/pmda_linux network.interface.speed
... then set breakpoints in places like refresh_net_dev_ioctl, then "r" in gdb.
cheers.
--
Nathan
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