SWAP size

Adrian Filipi-Martin adrian+freebsd-perf at ubergeeks.com
Wed Apr 30 14:50:48 PDT 2003

On Mon, 28 Apr 2003, Michael Nottebrock wrote:

> On Monday 28 April 2003 10:54, Piotr Rybicki wrote:
> > Hi everyone.
> >
> > In man tuning(7) we read, that swap size should be about 2x main memmory
> > size. Why swap size should be so big? Isn't swap size equal to main memmory
> > size enough?
> IMHO the swapsize=2x phys. mem size has always been just a rule of thumb. You
> need as much swap as you need (doh). But so far, the memory requirements of
> software have pretty much grown proportionally with the availibility /
> affordability of bigger sticks of memory and thus the rule of thumb still
> makes sense. YMMV.
> --
> Regards,
> 	Michael Nottebrock

	It used to mean something.  1x for swapping (whole processes) and
1x for paging (just pages of a process).  Each portion was used for exactly
one purpose.  This is no longer a valid reason though.  IIRC, it is because
FreeBSD has a unified buffer cache.

	I don't know if there are any other reasons for 2x.  I don't bothe
with more than 1x personally, if that much.  Swap space is really there for
emergencies only IMHO.

[ adrian at ubergeeks.com ]

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