Kernel swap zone exhausted, what is the max allowed? FBSD 7.2

Adam Vande More amvandemore at
Sat Feb 26 04:12:29 UTC 2011

On Fri, Feb 25, 2011 at 5:11 PM, Mark Terribile <materribile at>wrote:

> I don't explicitly set kern.maxswzone anywhere and it is at its apparent
> maximum and default of 32M (33554432).
> Does anyone know if the maximum can be increased?  (What actually is it
> used for?)  I do use lots of memory-intensive processes, most of them idle
> much of the time.  I see that it's involved with the stuff in the src/sys/vm
> directory.  Would someone give me a quick precis or pointer to what I need
> to study to understand what would happen if I tried to boost this to 64M?


vbox% sysctl -ad kern.maxswzone
kern.maxswzone: Maximum memory for swap metadata

man 8 loader gives:
                   Limits the amount of KVM to be used to hold swap meta
                   information, which directly governs the maximum amount of
                   swap the system can support.  This value is specified in
                   bytes of KVA space and defaults to 32MBytes on i386 and
                   amd64.  Care should be taken to not reduce this value
                   that the actual amount of configured swap exceeds 1/2 the
                   kernel-supported swap.  The default of 32MB allows the
                   nel to support a maximum of ~7GB of swap.  Only change
                   parameter if you need to greatly extend the KVM
                   for other resources such as the buffer cache or
                   kern.ipc.nmbclusters.  Modifies kernel option

Adam Vande More

More information about the freebsd-questions mailing list