On Fri, 09 Jan 2009 13:30:30 -0500
Lowell Gilbert <freebsd-questions-lo...@be-well.ilk.org> wrote:

> "PstreeM China" <pstr...@gmail.com> writes:
> > i think the option WRKDIRPREFIX  is a good idea , and i whill test
> > the methon unionfs.
> Definitely benchmark against just using a native local filesystem,
> though.  Taking away all of that memory that FreeBSD would otherwise
> use for *caching* file data could well end up making your builds
> *slower* with the MFS than they would have been without it.

I've a vague recollection that I tried something like this, a few years
ago, and found that the difference was too small to measure. 

I think that however you do it, you basically end-up with something that
looks like: 

   CPU/L1/L2 -> memory -> disk 

and whether the "memory->disk" part is a cached-file or swap-backed
memory is really just a matter of book-keeping - the VM system moves the
physical memory around as it likes. The book-keeping differences may be
significant, but they are not different in the electronic verses
electro-mechanical sense, and such intuitions may not relevant.

Poul-Henning Kamp, has an interesting article in this area for the
varnish project:

"I have spent many years working on the FreeBSD kernel, and only
rarely did I venture into userland programming, but when I had occation
to do so, I invariably found that people programmed like it was still


[Not that there's anything wrong with 1975.]
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