8.0-R-p2 ZFS: unixbench causing kmem exhaustion panic

[Doug Poland]

On Wed, January 13, 2010 12:35, Ivan Voras wrote:
>>>
>>> Try adding vfs.zfs.arc_max=512M to /boot/loader.conf.
>>>
>> Would you suggest tweaking the vm.kmem_size tunables in addition to
>> arc_max?
>
> No, unless they auto-tune to something lesser than approximately
> arc_max*3.
>
> I try to set arc_max to be a third (or a quarter) the kmem_size, and
> tune kmem_size ad_hoc to suit the machine and its purpose.
>
> The reason for this is that "arc_max" is just a guideline, not a hard
> limit... the ZFS ARC usage can and will spike to much larger values,
> usually in the most inopportune moment.
>
This is the state of the machine when it panicked this time:

panic: kmem_malloc(131072): kmem_map too small: 1296957440 total
allocated
cpuid = 1

/boot/loader.conf: vfs.zfs.arc_max=512M
vfs.numvnodes: 660
vfs.zfs.arc_max: 536870912
vfs.zfs.arc_meta_limit: 134217728
vfs.zfs.arc_meta_used: 7006136
vfs.zfs.arc_min: 67108864
vfs.zfs.zil_disable: 0
vm.kmem_size: 1327202304
vm.kmem_size_max: 329853485875

Using a handy little script I found posted in several places, I was
monitoring memory:

TEXT     15373968       14.66   MiB
DATA   1536957440       1465.76 MiB
TOTAL  1552331408       1480.42 MiB

Where TEXT = a sum of kldstat memory values
and   DATA = a sum of vmstat -m values

Is there a next step to try, or is this chasing a wild goose?


-- 
Regards,
Doug