On IBM AIX, Instana should not count filecache (completely) as "used_memory"

AIX by default uses available memory as filecache (between limits set by parameters minperm% and maxperm%), usually up to 90% of the total memory size. When the applications use only a small portion of available memory, the remainder (or large part of it) gets used for filecache. If applications (or the OS) need more memory, the filecache will shrink automatically. While technically correct, the "used memory" statistic from Instana is therefore less useful for triggering the "System memory almost exhausted" warning (in Instana itself) or as input to Turbonomic (for rightsizing memory).

It would be ideal if Instana would calculate something like a "needed memory" statistic, which does NOT include the current size of the filecache, but only a minimum amount of filecache (like 10% or the value of minperm% if that is larger). Ideally, this statistic could also include (a portion of) the used part of paging space, depending on the statistics of paging-in (from paging space): if 0 than the size of paging space need not be considered, the larger that number gets the more used paging space should be added to the "needed memory" number.

I realize that we can create a custom metric for this (creating a script that writes things to statsd, to be read by Instana). The trouble is that all of our systems need to get the same script. And IBM Turbonomic has no way of 'rightsizing' memory, if it only has "used memory" to work with. There should be a standardized metric for "needed memory" that Instana calculates, uses itself AND can be forwarded to other tools like Turbonomic.

If the customer uses PowerVC, Instana should also request the HMC partition name of the current lpar (uname -L) to forward this to Turbonomic too, so the memory data can be correlated (stitched) to the CPU data of the corresponding lpar.