Freebsd 8.0 kmem map too small
freebsd at jdc.parodius.com
Mon May 3 11:01:01 UTC 2010
On Mon, May 03, 2010 at 12:41:50PM +0200, Giulio Ferro wrote:
> NFS server amd64 Freebsd 8.0 recent (2 days ago)
> This server has been running for several months without problems.
> Beginning last week, however, I'm experiencing panics (about 1 per day)
> with the error in the subject
> Current settings:
> vm.kmem_size_scale: 3
> vm.kmem_size_max: 329853485875
> vm.kmem_size_min: 0
> vm.kmem_size: 2764046336
> hw.physmem: 8568225792
> hw.usermem: 6117404672
> hw.realmem: 9395240960
> vfs.zfs.l2arc_noprefetch: 0
> vfs.zfs.l2arc_feed_secs_shift: 1
> vfs.zfs.l2arc_feed_secs: 1
> vfs.zfs.l2arc_headroom: 128
> vfs.zfs.l2arc_write_boost: 67108864
> vfs.zfs.l2arc_write_max: 67108864
> vfs.zfs.arc_meta_limit: 431882240
> vfs.zfs.arc_meta_used: 431874720
> vfs.zfs.arc_min: 215941120
> vfs.zfs.arc_max: 1727528960
> I've set nothing in either /boot/loader.conf or sysctl.conf
> What should I do?
You need to adjust vm.kmem_size to provide more space for the ARC.
Below are ZFS-relevant entries in our /boot/loader.conf on production
RELENG_8 systems with 8GB of RAM. The reason we set kmem_size to half
our physical system memory is because I didn't want to risk other
processes which use a larger maxdsiz/dfldsiz/maxssiz to potentially
exhaust all memory.
# Increase vm.kmem_size to allow for ZFS ARC to utilise more memory.
# Disable ZFS prefetching
# Increases overall speed of ZFS, but when disk flushing/writes occur,
# system is less responsive (due to extreme disk I/O).
# NOTE: 8.0-RC1 disables this by default on systems <= 4GB RAM anyway
# NOTE: System has 8GB of RAM, so prefetch would be enabled by default.
# Decrease ZFS txg timeout value from 30 (default) to 5 seconds. This
# should increase throughput and decrease the "bursty" stalls that
# happen during immense I/O with ZFS.
| Jeremy Chadwick jdc at parodius.com |
| Parodius Networking http://www.parodius.com/ |
| UNIX Systems Administrator Mountain View, CA, USA |
| Making life hard for others since 1977. PGP: 4BD6C0CB |
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