Dave Shield wrote on 2006-02-24:
> As watchers of the CVS list will have realised, I've been doing some
> work on the UCD 'memory' group, and I've come across a couple of
> inconsistencies, which I thought I'd mention here.
> 
>   a)  Should 'memSwapError' monitor 'memAvailSwap' or 'memTotalFree' ?
>       Different architectures implement this differently

I think the MIB descriptions imply monitoring *swap* space, so I'd stick
to that, even though monitoring available *virtual* memory might make
more sense to users.

How is this currently implemented in 5.4.rc1?

>   b)  Should 'memAvailSwapTXT' and 'memAvailRealTXT' report the
>       amount of memory free, or the amount used?
>       The MIB object name implies one, the description the other!
> 
> I think this latter is only applicable to HP-UX, and the code actually
> reports the amount used.  But the name of the MIB objects is misleading.

I think it should be clarified in the MIB object description that the
object name is bogus, ideally before we ship 5.4.

I'd also like to raise another issue with UCD-SNMP_MIB::memory and the
mem HAL:

c) Both the MIB and the mem HAL struct seem to use the phrases "free"
and "available" [memory] quite interchangeably, although to the best of
my knowledge there's a whole lot of difference between "free" (i.e.
currently totally unused) and "available" (to applications on request,
even if currently used by the system for buffer/cache purposes) memory
on most modern OSes.

FWIW, from an admin's perspective, I'd be much more interested in
monitoring "available" than "free" memory, because I'd always trust a
decent OS kernel to do something useful with unused memory without
affecting my monitoring.


+Thomas

-- 
Thomas Anders (thomas.anders at blue-cable.de)

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