[Ocfs2-users] memory leak

[Joel Becker]

On Thu, Apr 15, 2010 at 12:31:02PM +0200, Kristiansen Morten wrote:
> I discovered our four node cluster running on RedHat EL5, Ocfs2 1.2.6 and Oracle 10.2.0.3 have memory leak. I suspect ocfs2, but I could be wrong. I suspect ocfs2 because when we run RMAN backup the free memory goes from 8 GB down to 200 MB. When I umount the ocfs2 backupdisk after the backup is finished, the memory is released again.

	You don't have a memory leak.  Your backup is reading every file
into cache in order to process it.  This is a normal behavior of
filesystem cache.  If other processes need memory, the file data will be
evicted from cache.

> I want to test it some more and found a script to test writing to the disk. This script contains a command saying "echo 3 > /proc/sys/vm/drop_caches". Is this a safe command to run in production? Meaning the cluster and oracle database is running. Or should I run the "sync" command pre to this command? Or should I never run this command in a production environment? I'm afraid that this command will free up memory not written to disk yet. And therefore I would get into trouble in my production environment. The script I want to test looks like this and is captured from this mailing list:

	The command "echo 3 > /proc/sys/vm/drop_caches" is safe to run
in a production environment.  However, I don't think you want to do so.
What it does is evicts all file data from cache.  Don't worry, you won't
lose any data.  But you will not only evict the data from the backup
volume, you will also evict data from any other file.  This may slow
down some processes as they have to re-read their data.
	Why do you feel there is a problem?  Is it just that the free
memory number shrinks?  That's not a problem, as stated above.  Is there
some other affect on the system?

Joel

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Joel Becker
Principal Software Developer
Oracle
E-mail: joel.becker at oracle.com
Phone: (650) 506-8127