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List:       gfs-devel
Subject:    Re: selecting amount of memory available to DME
From:       Mike Tilstra <conrad () sistina ! com>
Date:       2000-07-20 14:38:28
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On Wed, Jul 19, 2000 at 06:58:47PM -0500, Andrew Barry wrote:
> Just to offer a base-line, the DMEP lock module has a compile-time flag
> for the maximum number of clients in a cluster. The default is 32 clients
> maximum. For this the data size of each buffer needs to be 18 bytes. If
> this is stored on the DMEP device in a singly-linked hash-table with 32bit
> pointers that's about 50 bytes per buffer. Ken has indicated that it would
> not be unusual for a client to hold 30,000 locks at a time. (now that
> Nopen counts are locks and not on disk, and that there are multiple locks
> per inode) so count on 1.5MB-2MB per client. So realistically about 64MB
> of Buffers is necessary for a 32 client segment. 
> There might be more than one RAID, but there might also be more than one
> filesystem too. 

here's a real example.  Two machines comfotable fit in the space that the
current memexpd server gives for defaults, which is about 6.5M for 98304
memory elements.  wednesday, after about an hour of running make_panic on
both nodes, there was about 11000 elements still unused.  I'm not sure if
this is a real value or a leak yet though....

-- 
Mike Tilstra                          tilstra@borg.umn.edu
Anonymity is the beauty of going online.
You don't know who I am.
You hope I don't know who you are.

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