[Proof of Concept] Stacked unionfs based 'tinderbox'
uqs at FreeBSD.org
Thu Feb 25 13:53:07 UTC 2010
On Thu, 25.02.2010 at 10:08:15 +0200, David Naylor wrote:
> As some may have noticed on -current I have been working on using
> stacked unionfs to implement a 'tinderbox' type build system. I have
> successfully used the scripts to build x11/xorg (and have compared the
> results to using the traditional approach using pkg_add). The build
> system is stable except for one nasty corner case: deadlocks.
When I did this a couple of years ago, the major problems were failing
chdir(2) calls during ports build, etc.
> To setup a compatible test environment requires:
> - recompile the kernel with `options KSTACK_PAGES=32`, otherwise the
> kernel will panic with a double fault. WITNESS options results in
> substantial performance degradation.
> - patch mtree (see below) [optional]
> - create the appropriate chroot environment (and reboot) [see below
> for corner case]
> A performance bottleneck in mtree was identified. This resulted in
> mtree (as run by port install) consuming ~20% of the build time. See
> bin/143732 for a patch and further details.
> The normal tinderbox approach takes ~80% more time to install compared to the
> quick and dirty approach. The stacked unionfs approach takes ~170% more time
> (an increase of ~50% over the tinderbox approach). Some performance gains can
> be had if one uses memory backed storage (vs HDD in this case).
Please explain: what is the quick and dirty approach and which one is
As your scripts did not make it through, perhaps you can upload them to
the wiki? What I did back then was using a clean base system as the
underlying unionfs store to avoid re-generating the clean base over and
over again. Nowadays, a ZFS clone would probably be the way to go.
I'm not sure if a recursive approach is feasible here, as you can have
only one underlying unionfs mount. But special casing, e.g., perl may
still give a massive speedup. So for each port that has perl as
dependancy, you would not pull in the clean base + pkg_add perl, but
instead grab the clean-base+perl directory as an underlying unionfs.
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