is TMPFS still highly experimental?

[Jeremy Chadwick]

On Sat, Oct 01, 2011 at 06:02:39PM -0700, Xin LI wrote:
> On Sat, Oct 1, 2011 at 8:48 AM, Chris Rees <crees at freebsd.org> wrote:
> > I've also not heard of anyone using it with zfs successfully- it tends to
> > shrink rapidly.
> 
> I'm quite surprised with this assertion.  I use tmpfs on my own system
> and I never see such problem as long as one have sufficient swap
> space.
> 
> Not to say there is no problem --there is no way to say "commit this
> amount of memory to ZFS" but really I have never hit this exact
> alleged problem...

Its been reported multiple times by multiple people, and there has been
no official word on -fs, -stable, or zfs-devel that this specific
problem has been fixed:

* miyamoto moesasji
  - 2011/01/01
  - 8.2-PRERELEASE (thus RELENG_8)
  - World/kernel build date unknown
  - http://lists.freebsd.org/pipermail/freebsd-stable/2011-January/060850.html
  - http://lists.freebsd.org/pipermail/freebsd-stable/2011-January/060852.html
  - http://lists.freebsd.org/pipermail/freebsd-stable/2011-January/060860.html
  - http://lists.freebsd.org/pipermail/freebsd-stable/2011-January/060861.html
  - Statement from Ivan Voras that it's a known problem:
  - http://lists.freebsd.org/pipermail/freebsd-stable/2011-January/060867.html

* Atilla Nagy
  - 2011/01/19
  - 8.2-PRERELEASE (thus RELENG_8)
  - World/kernel build date of 2011/01/08
  - http://lists.freebsd.org/pipermail/freebsd-fs/2011-January/010496.html
  - http://lists.freebsd.org/pipermail/freebsd-fs/2011-January/010497.html
  - http://lists.freebsd.org/pipermail/freebsd-fs/2011-January/010498.html
  - http://lists.freebsd.org/pipermail/freebsd-fs/2011-January/010499.html
  - http://lists.freebsd.org/pipermail/freebsd-fs/2011-January/010501.html
  - http://lists.freebsd.org/pipermail/freebsd-fs/2011-January/010569.html
  - Ivan Voras mentions a thread he started on -CURRENT circa 2010/11/21
    about this problem:
    http://www.mail-archive.com/freebsd-current@freebsd.org/msg126491.html

* Michael Loftis
  - 2009/12/08
  - FreeBSD 8.0-RELEASE (RELENG_8_0)
  - World/kernel build date of 2009/11/21
  - Might be a different problem altogether, but tmpfs is explicitly
    mentioned in the fix/commit text from avg@
  - http://www.freebsd.org/cgi/query-pr.cgi?pr=kern/141305

Plus Chris Rees' report.  So that makes 3, possibly 4 if you consider
the PR from Michael Loftis.

Possibly it has something to do with the exact FreeBSD version they're
using.  Not just version (e.g. 8.2-RELEASE vs. 8.2-STABLE), but also
kernel/world build date -- because as we've established, ZFS changes are
happening all the time and there is very little transparency when it
comes to communicating these changes to the community.

Maybe the problem has been fixed in RELENG_8 sometime after 2011/01/08,
but we do not know.  ZFS committers would need to help.  Else, folks
should be reaching out to the first two people I mentioned above and
asking if they can reproduce the problem on present-day RELENG_8.

-- 
| Jeremy Chadwick                                jdc at parodius.com |
| Parodius Networking                       http://www.parodius.com/ |
| UNIX Systems Administrator                   Mountain View, CA, US |
| Making life hard for others since 1977.               PGP 4BD6C0CB |