[PVE-User] Show memory usage w/o buffer/cache in VM summaries?

[Frank Thommen]

Dear all.

the memory usage bar in the VM summaires in PVE (6.1-3) shows "active" 
memory including caches, which is in practice misleading.  E.g. this 
system

$ free -m
               total        used        free      shared  buff/cache 
available
Mem:           7821        4778         177          51        2864 
   2738
Swap:          3276         123        3153
$

is shown as using 7.46 GB memory, in red warning color, since this 
number exceeds 90% of the available 8 GB.  However IMHO the almost 3 GB 
memory used as buffer/cache are irrelevant as they will be freed as soon 
as they are required by applications.  Hence I'd rather see the bar 
showing me only 4.8 GB of used memory.

Is that achievable?  The guest OS is CentOS 7.x.  The qemu gest agent is 
installed.

Cheers, Frank