ZFS performance issues (solved?!)

Arnaud Houdelette arnaud.houdelette at tzim.net
Mon Sep 1 15:21:58 UTC 2008

Wes Morgan a écrit :
> <div class="moz-text-flowed" style="font-family: -moz-fixed">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.
I had really bad performance before removing the line. I had to disable 
zil on zfs (my /usr/src is on zfs) to be able to recompile, as one of 
the zil process was eating up nearly all off the CPU.

After rebuild/install kernel, no problems anymore. Thanks.

I second the above suggestion about opensolaris. There's no mention 
anywhere of this module (or at least, I didn'it find one before), on 
UPDATING nor on the list of what this module is for ?

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