Re: On FC host statistics ( /sys/class/fc_host/hostX/statistics) and monitoring plugins

["Martin K. Petersen" <martin.petersen@oracle.com>]

Ulrich,

> 1) Some numbers (e.g. fcp_frame_alloc_failures) are not supported by
> some drivers (e.g. QLE2690) and the value read from the file is
> "0xffffffffffffffff". The source seems to set this to -1, but when
> reading it back it looks like unsigned. For a 64-bit counter it's
> quite unlikely to read this value, but it's still possible.

I agree that's messy.

> 2) While statistics counters seems to be 64 bits, I've experienced a
> "wrap around" at fewer bit positions (maybe like 40 bits) for the bfa
> driver. I have no idea whether it's a hardware restriction or a
> firmware/driver bug, however. I did my best to make sure it's not a
> problem of my plugin (assuming those counters are read atomically when
> using one read())

bfa has been dead for about 5 years so don't expect any fixes in that
department.

> My idea was (probably more universal than restricted to FC host
> statistics) to provide another file (maybe named "statistics") that
> lists the names of implemented statistics counters (i.e.: leaving out
> those set to -1) together with the significant bits (like 32 or 64),
> the type of the value (like "counter", "gauge", "boolean", "enum",
> "string", etc.)
> "string" would be free text (I doubt it will make sense for
> statistics, but anyhow), "enum" would be single word tokens
> (e.g. _not_ " NPort (fabric via point-to-point)"), "counter" would
> count bytes or events (maybe a type "event_count[er]" may make sense),
> and "gauge" would be a non-monotonic value like utilization...

I'm not a particularly big fan of -1 reporting. But it seems that the
path of least resistance is to fix the sysfs unsigned issue.

-- 
Martin K. Petersen	Oracle Linux Engineering