Memory leak in ZFS?

[Pawel Jakub Dawidek]

On Thu, Jan 13, 2011 at 12:36:51AM +0000, Nik Azam wrote:
> Hi all,
> 
> For the past few weeks, I noticed that the amount of memory reported in top
> (sum of active, inact, wired, cache buf and free) keeps decreasing as the
> uptime increases. I can't pinpoint to when I first noticed this, as I have
> updated the system a few times just in case this has been fixed.
> 
> The box has 8GB of RAM, running 8.2-PRERELEASE r216693. The ZFS pool
> consists of two RAIDZ1 with 5 disks each and 50GB L2 ARC. Root filesystem is
> on UFS on separate disk. I have samba, netatalk, istgt, mysql and apache
> running on the box.
> 
> After booting up, top reports I have 8GB of memory as expected. After moving
> files around in the ZFS pool, the ARC grows to 4GB (the maximum size I set).
> Now the box has been up for 10 days, and the sum of memory reported in top
> is about 4GB (3GB wired). ARC size is about 2GB. I tried stopping all the
> services running, but this didn't help. When unmounting the ZFS pool (via
> /etc/rc.d/zfs stop), top reports that I have 8GB again. Throughout the 10
> days period, there is no user activity at all to the UFS filesystem.
> 
> Is there anything sinister happening here? Or is it just top is playing
> tricks on me?

The easiest way to check for memory leaks is to export the pool and
unload zfs.ko. If the leaks exist, they will be reported on the system
console.

-- 
Pawel Jakub Dawidek                       http://www.wheelsystems.com
pjd at FreeBSD.org                           http://www.FreeBSD.org
FreeBSD committer                         Am I Evil? Yes, I Am!
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