Still getting kmem exhausted panic

[Andriy Gapon]

on 28/09/2010 16:25 Willem Jan Withagen said the following:
> Well advises seem to vary, and the latest I understood was that
> 8.1-stable did not need any tuning. (The other system with a much older
> kernel is tuned as to what most here are suggesting)
> And I was shure led to believe that even since 8.0 panics were no longer
> among us......

Well, now you have demonstrated yourself that it is not always so.

>> vm.kmem_size
>> vfs.zfs.arc_max
> 
> real memory  = 12889096192 (12292 MB)
> avail memory = 12408684544 (11833 MB)
> 
> So that prompts vm.kmem_size=18G.
> 
> Form the other post:
>> As to arc_max/arc_min, set them based your needs according to general
>> ZFS recommendations.
> 
> I'm seriously at a loss what general recommendations would be.

Have you asked Mr. Google? :)
- http://www.solarisinternals.com/wiki/index.php/ZFS_Best_Practices_Guide
  Search for "Memory and Dynamic Reconfiguration Recommendation"
-
http://www.solarisinternals.com/wiki/index.php/ZFS_Evil_Tuning_Guide#Limiting_the_ARC_Cache

Short version - decide how much memory you need for everything else but ZFS ARC.
If autotuned value suits you, then you don't need to change anything.

> The other box has 8G
> loader.conf:
> vm.kmem_size="14G"      # 2* phys RAM size for ZFS perf.
> vm.kmem_size_scale="1"

No need to set both of the above.  vm.kmem_size overrides vm.kmem_size_scale.

> vfs.zfs.arc_min="1G"
> vfs.zfs.arc_max="6G"
> 
> So I'd select something like 11G for arc_max on a box with 12G mem.

-- 
Andriy Gapon