kmem_map too small with ZFS and 8.2-RELEASE
mcdouga9 at egr.msu.edu
Fri Mar 4 13:41:18 UTC 2011
On 03/04/11 04:48, Mickaël Canévet wrote:
>> I'd use vm.kmem_size="32G" (i.e. twice your RAM) and that's it.
> Should I also increase vfs.zfs.arc_max ?
> Do you have any idea why the kernel panicked at only 8GB allocated ?
> Thank you
I believe ARC allocations in kmem can become fragmented, so when it is
searching for a place to store a new contiguous segment of memory, the
remaining fragmented free spaces may all be too small. I also set
vm.kmem_size to about twice the amount of ram to help it avoid this
issue. I suspect if kmem is badly fragmented then performance of ZFS
can downgrade, so that is another reason to keep kmem bigger.
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