[CFT] ZFS v15 patch (version 3)

Peter Jeremy peterjeremy at acm.org
Thu Jul 8 20:05:42 UTC 2010

On 2010-Jul-05 13:50:52 +0200, Martin Matuska <mm at FreeBSD.org> wrote:
>As ZFS v15 is already being used in the Solaris 10 enterprise world, we
>can consider it well-tested.

So we know if the ZFS in Solaris 10 includes any fixes that aren't
publicly available?

>Direct link to the patch:
>The patch applies cleanly against head and stable/8.

In order to apply it to a two-week-old stable/8, I needed to:
# mkdir cddl/contrib/opensolaris/lib/pyzfs
# mkdir cddl/contrib/opensolaris/lib/pyzfs/common
# mkdir cddl/contrib/opensolaris/cmd/pyzfs

Other than verifying that it applies (with the above change), compiles
and runs, I haven't attempted any stress tests yet.

Looking at the patchset, the most critical issue (IMHO) that doesn't
appear to have been addressed is the interaction between ZFS ARC and
the VM cache used by UFS/NFS: arc_memory_throttle() is still making
decisions solely on the amount of "free" memory, without considering
"inactive" or "cache".  I am running a slight variant of a patch by
Artem Belevich (see http://pastebin.com/ZCkzkWcs) but he acknowledges
that patch is incomplete (and I've managed to wedge one of my systems
a couple of times whilst doing zfs send/recv).

Without patching arc_memory_throttle(), a system behaves especially
poorly if it uses ZFS with any of mmap(2), UFS or NFS client - in my
case, ports/mail/mairix was almost guaranteed to wedge the system.
This is the problem that the following hack is intended to work around:
  perl -e '$x = "x" x 1000000;'

Peter Jeremy
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