[Beowulf] SWAP management

Butti Gabriele - Dottorati di Ricerca gabriele.butti at unimib.it
Thu Dec 11 10:25:06 EST 2003


Hi everybody,
      the question I am going to ask is not strictly releted to a
beowulf cluster but has to do with scientific computing in general, also
with scalar codes. I would like to learn more on how swap memory pages
are handled by a Linux OS. 
My problem is that when I'm running a code, it starts swapping even if
its memory requirements are lower than the total amount of memory
availble. For exaple if there 750 Mb of memory, the program swaps when
using only 450 Mb. How can avoid such a thing to happen? One solution
could be not to create any SWAP partition during the installation but I
think this is a very dramatic solution. 
Is there any other method to force a code to use only RAM ?
It seems that my Linux OS [RH 7.3 basically, in some cases SuSE 8.2]
tries to avoid that the percentage of memory used by a single process
becomes higher than 60-70 %.
Any idea would be appreciated.
TIA
Gabriel
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