ZFS patches.

[Antony Mawer]

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.