wrong memory stats with collectd

Hi,

I have configured collectd to poll memory usage on my 32GB vmd server
and it seems the numbers are wrong. I have configured collectd to write
into CSV just to be sure it wasn't an rrd or influxdb issue.

I have configured the memory plugin as such:
<Plugin memory>
ValuesAbsolute true
ValuesPercentage true
</Plugin>

Collectd outputs:
==> memory-active-2019-09-24 <==
1569361743.219,1491005440.000000

==> memory-free-2019-09-24 <==
1569361743.219,394997760.000000

==> memory-inactive-2019-09-24 <==
1569361743.219,1246621696.000000

vmstat says:
procs memory page disks traps cpu
r s avm fre flt re pi po fr sr sd0 sd1 int sys cs us sy id
1 129 5518M 24952M 63 0 0 0 0 0 2 0 34 707 610 0 0 99

On my vms, running with 4GB of RAM or less, values seem coherent between
collectd and vmstat.

I found an old bug track that seems to describe this issue:
https://github.com/collectd/collectd/issues/1991

Could this be a bug in collectd or am I doing something wrong?

I'm using collectd 5.8.1 on OpenBSD 6.5/amd64.

TIA,
Jo