Date: Tue, 29 Jul 2008 07:18:03 +1000 From: Antony Mawer <fbsd-fs@mawer.org> To: OutBackdingo <outbackdingo@gmail.com> Cc: freebsd-fs@freebsd.org, Max Laier <max@love2party.net>, freebsd-current@freebsd.org, Pawel Jakub Dawidek <pjd@FreeBSD.org> Subject: Re: ZFS patches. Message-ID: <488E378B.40406@mawer.org> In-Reply-To: <1217250051.6657.0.camel@dingo-laptop> References: <20080727125413.GG1345@garage.freebsd.pl> <200807272034.01290.max@love2party.net> <20080728083303.GD2953@garage.freebsd.pl> <200807281454.36892.max@love2party.net> <20080728125711.GH2953@garage.freebsd.pl> <1217250051.6657.0.camel@dingo-laptop>
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I have a single-disk i386 system with 1GB RAM, 512MB kmem, which now
appears to be perfectly stable... It's a Via Epia system (C3 1GHz) so
it's not exactly high-end hardware.
This is running 7-STABLE from ~16 May 2008 (without the most recent
patches applied), and the following configuration in /boot/loader.conf:
# Root on ZFS
zfs_load="YES"
vfs.root.mountfrom="zfs:tank"
# Tune kernel KVA space
vm.kmem_size="512M"
vm.kmem_size_max="512M"
# Tune ZFS arc and vdev cache sizes
vfs.zfs.arc_min="16M"
vfs.zfs.arc_max="40M"
vfs.zfs.vdev.cache.size="5M"
# Disable prefetch to improve performance
vfs.zfs.prefetch_disable="1"
Some of these tunings may be superfluous, but until I added them
recently the box never lasted more than 2-3 days. It's now been up for 3
weeks without a panic. Kernel memory usage is comfortable:
# kmem
TEXT=6285036, 5.99388 MB
DATA=93330432, 89.0068 MB
TOTAL=99615468, 95.0007 MB
The kmem script is the one posted on the FreeBSD wiki. The highest I
have seen it climb is ~102mb, which to me suggests I can afford to tune
the vfs.zfs.arc_max value higher (I started out with a conservatively
low value and planned to tune and tweak from there based on observing
kernel memory usage).
--Antony
OutBackdingo wrote:
> So are we saying that i386 with a default kmem of 512MB has gotten
> psuedo stable with some load?
>
> On Mon, 2008-07-28 at 14:57 +0200, Pawel Jakub Dawidek wrote:
>> On Mon, Jul 28, 2008 at 02:54:36PM +0200, Max Laier wrote:
>>> On Monday 28 July 2008 10:33:03 Pawel Jakub Dawidek wrote:
>>>> Yes, it should fix most if not all 'kmem_map too small' panics, at least
>>>> from what I tried. Tunning kmem_size is still needed to get better
>>>> performance.
>>> With the i386 default settings it was not too hard to get the attached panic.
>>> Some cpdup and rm cycles of src and ports to a single disk zfs pool. With
>>> 512M I haven't been able to kill it, yet.
>> I was probably too optimistic. The default kmem_size is probably just
>> too low. I'm quite sure it would be too low even for Solaris.
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