swap or not?
scheinin at crs4.it
Tue Feb 5 10:26:29 EST 2002
Galen Arnold wrote:
> I'm looking for some opinions (based on real cluster setups would be nice
> too). If you've got nodes with lots of memory (>1GB) do you run with swap
> space configured or not?
> We're seeing the occasional run that misses its memory request by a lot
> and it hangs nodes due to excessive paging.
I recommend having swap space, perhaps half a gigabyte. At the same time,
if a job uses alot of page, it must be killed without remorse. To be
notified of the problem, I suppose (I have not tried it) you can
modify a script of Big Brother. My point is, these days, when even
main memory is considered slow relative to level one cache, a job that
pages to disk will take a very, very long time to finish in comparison
to the same job with a smaller dataset that does not use swap. On the
other hand, there may be jobs that need the extra space for a limited
amount of time, in which case the swap space would be useful.
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