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Re: [Linux-cluster] optimising DLM speed?



On 02/17/2011 01:29 PM, David Teigland wrote:
On Thu, Feb 17, 2011 at 09:24:41PM +0000, Alan Brown wrote:
David Teigland wrote:
Don't change the buffer size, but I'd increase all the hash table sizes to
4096 and see if anything changes.

echo "4096">  /sys/kernel/config/dlm/cluster/rsbtbl_size
echo "4096">  /sys/kernel/config/dlm/cluster/lkbtbl_size
echo "4096">  /sys/kernel/config/dlm/cluster/dirtbl_size
Increasing rsbtbl_size to 4096 or higher results in FSes refusing to
mount and clvm refusing to start - both with "cannot allocate
memory"

At 2048, it works, but gfs_controld and dlm_controld exited when I
tried to mount all FSes on one node as a test.

At 1024 it seems stable.

The other settings seemed to have applied OK. So far, reports are
positive (but it's quiet at the moment)

I've got a strace of clvmd trying to start with rsbtbl_size set to
4096. Should I post it here or would you prefer it mailed direct?
Thanks for testing, you can post here.
Hi all. After two tries, we've modified our cluster so that all nodes have increased their dlm hash table sizes to 1024. Initially, I put the echos in /etc/init.d/gfs2, but it turns out that /etc/init.d/gfs2 is sort of a no-op: /etc/init.d/netfs mounts the gfs2 filesystems before /etc/init.d/gfs2 is ever called, so the echos need to be before netfs.

At any rate, we have noticed a significant perceived improvement in overall performance of the systems. Where before, it was common to see imap process in D wait -- sometimes hanging for long periods of time -- we have not seen that at all since updating the hash table size. So far, so good!

-- scooter


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