ZFS performance issues (solved?!)

Wes Morgan morganw at chemikals.org
Mon Sep 1 10:48:39 UTC 2008

On Mon, 1 Sep 2008, John Birrell wrote:

> For those people experiencing a performance degradation since the DTrace 
> import, please update your copy of 
> src/sys/cddl/compat/opensolaris/kern/opensolaris_kmem.c by either cvsup 
> of direct edit to remove "#define KMEM_DEBUG".
> You only need to rebuild the opensolaris kernel module after this 
> change. The code is shared between ZFS and DTrace via the opensolaris 
> kernel module.
> This is also the reason why you found it necessary to add KDB, DDB and 
> STACK to your kernel. After removing KMEM_DEBUG, you won't need those.
> Please confirm that this solves the problem you have been seeing.

8 or so hours later and everything is good here.

One other suggestion, the "opensolaris" module that is now required for 
zfs is not mentioned anywhere in UPDATING. Users of "MODULES_OVERRIDE" 
will likely find themselves with a system that will not boot without 
manual intervention, sometimes even requiring a live cd. A headsup or 
warning would probably be appreciated by other zfs'ers.

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