[Beowulf] Parallel memory

Bogdan Costescu Bogdan.Costescu at iwr.uni-heidelberg.de
Wed Oct 19 05:53:10 EDT 2005


On Tue, 18 Oct 2005, Robert G. Brown wrote:

> There was once also an online list discussion about swapping to an 
> NFS mounted remote exported ramdisk

There are some problems with this approach, which is in principle very 
similar with swapping over NBD or iSCSI. A discussion about iSCSI just 
happened 1-2 months ago on the netdev and linux-kernel mailing lists; 
the main problem is what to do in case the memory becomes tight: a 
part of memory has to be sent to the block device, but sending it 
requires allocating more memory for the network transfer; sometimes 
some part of memory is sent out just so that another part is copied 
back in, in which case more memory is needed for the network transfer 
(for the reception) - both these situations can result in a deadlock.
So, swapping over network is not (yet) that reliable - doing this at 
the application level, therefore knowing more-or-less the pattern of 
transfers, seems much wiser.

-- 
Bogdan Costescu

IWR - Interdisziplinaeres Zentrum fuer Wissenschaftliches Rechnen
Universitaet Heidelberg, INF 368, D-69120 Heidelberg, GERMANY
Telephone: +49 6221 54 8869, Telefax: +49 6221 54 8868
E-mail: Bogdan.Costescu at IWR.Uni-Heidelberg.De
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