[Linux-cluster] GFS: drop_count and drop_period tuning

Claudio Tassini claudio.tassini at gmail.com
Tue Sep 11 08:35:43 UTC 2007

Thanks Michael, I've set this option on my filesystems. How should this
impact to the system performance/behaviour? More/less memory usage? I guess
that, by trimming the 50% of unused locks every 5 secs, it should cut off
memory usage too.. am I right?
If this works, I could also raise the drop_count value?

2007/9/10, Hagmann, Michael <Michael.Hagmann at hilti.com>:
>  Hi
> When you are on RHEL4.5 then I highly suggest you to use the new
> glock_purge Parameter for every gfs Filesystem add to /etc/rc.local
> -------
> gfs_tool settune / glock_purge 50
> gfs_tool settune /scratch glock_purge 50
> -------
> also this Parameter has to set new on every mount. That mean when you
> umount it and then mount it again, run the /etc/rc.local again, otherway the
> parameter are gone!
> maybe also checkout this page --> http://www.open-sharedroot.org
> /Members/marc/blog/blog-on-gfs/glock-trimming-patch
> mike
>  ------------------------------
> *From:* linux-cluster-bounces at redhat.com [mailto:
> linux-cluster-bounces at redhat <linux-cluster-bounces at redhat.com>.com<linux-cluster-bounces at redhat.com>]
> *On Behalf Of *Claudio Tassini
> *Sent:* Montag, 10. September 2007 13:19
> *To:* linux clustering
> *Subject:* [Linux-cluster] GFS: drop_count and drop_period tuning
> Hi all,
> I have a four-nodes GFS cluster on RH 4.5 (last versions, updated
> yesterday). There are three GFS filesystems ( 1 TB, 450 GB and 5GB), serving
> some mail domains with postfix/courier imap in a "maildir" configuration.
> As you can suspect, this is not exactly the best for GFS: we have a lot
> (thousands) of very small files (emails) in a very lot of directories. I'm
> trying to tune up things to reach the best performance. I found that tuning
> the drop_count parameter in /proc/cluster/lock_dlm/drop_period , setting
> it to a very large value (it was 500000 and now, after a memory upgrade,
> I've set it to 1500000 ), uses a lot of memory (about 10GB out of 16 that
> I've installed in every machine) and seems to "boost" performance limiting
> the iowait CPU usage.
> The bad thing is that when I umount a filesystem, it must clean up all
> that locks (I think), and sometimes it causes problems to the whole cluster,
> with the other nodes that stop writes to the filesystem while I'm umounting
> on one node only.
> Is this normal? How can I tune this to clean memory faster when I umount
> the FS? I've read something about setting more gfs_glockd daemons per fs
> with the num_glockd mount option, but it seems to be quite deprecated
> because it shouldn't be necessary..
> --
> Claudio Tassini
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Claudio Tassini
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