Following vm_lowmem event handler for dirhash
Nick Barkas
snb at freebsd.org
Sat Jun 20 16:13:31 UTC 2009
On Fri, Jun 19, 2009 at 09:46:40AM +0200, Kamigishi Rei wrote:
> Hello, hope you're having a nice day,
>
> Following
> http://lists.freebsd.org/pipermail/freebsd-current/2009-May/007367.html
>
> > It adds a vm_lowmem event handler to the dirhash code in UFS2
> > so that dirhashes will be deleted when the system is low on memory.
> From what I gather, this patch is in -CURRENT now; I've updated to
> -CURRENT 3 days ago (after using a snapshot from May) and my previously
> stable system threw a kernel panic yesterday. Panic happened during a
> benchmark on my ZFS pool (bonnie++ -s 32768) supposedly because of that
> exact patch (because ZFS is known to eat a lot of kmem and vm_lowmem was
> probably triggered). Alas, I don't have a dump available (because my
> system boots from a geom mirror and the swap space is there as well), so
> I only have the panic message: "dirhash: NULL hash on list".
You probably don't have the latest changes made to dirhash, which I
committed in r194387 on the 17th of June. That fixed some problems
introduced in my first commit with the vm_lowmem handler for dirhash a
couple of weeks ago. Until this latest commit, it is possible that
ufsdirhash_destroy(), which is where your "dirhash: NULL hash on list"
message comes from, might be trying to destroy an already deleted
dirhash. Please try updating your sources and build a new kernel to see
if this problem comes up again.
Nick
> My system is a Core2 Duo on a Q35 motherboard, using 2GB RAM and 4x
> 500GB drives, of which 2 are in a GEOM_MIRROR and the other 2 are in a
> zpool.
>
> fujibayashi at ameagari ~ % uname -a
> FreeBSD ameagari.fujibayashi.jp 8.0-CURRENT FreeBSD 8.0-CURRENT #0: Tue
> Jun 16 21:50:53 JST 2009
> root at ameagari.fujibayashi.jp:/usr/obj/usr/src/sys/Ameagari amd64
>
> (Last line in /usr/src/UPDATING states "20090613".)
>
> --
> Kamigishi Rei
> Systems Administrator
> WIDE
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