Please explain FreeBSD 8.0/ZFS memory usage patterns

Ivan Voras ivoras at
Tue Jan 12 14:35:36 UTC 2010

Benjamin Lutz wrote:
> Hello,
> I've set up a FreeBSD-8.0/amd64 system with ZFS as a home server, and I'm a 
> bit puzzled by it's memory usage pattern; I'm seeing total memory usage 
> oscillate between roughly 50% and 90% of my RAM. So I've tracked memory 
> usage over the course of about 12 hours and graphed it here:

How do you get those categories: kern, proc? I suppose proc could be sum 
of resident sizes of processes (aka "RES" in top) and kern could be 
sysctl vm.kmem_size?

> In the first half of the graph, there's a torrent download running, which I 
> assume causes the large fluctuations in memory usage. However, memory usage 

Large fluctuations in which category? The ARC? (since "proc" doesn't 
fluctuate much).

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