Swap over the network?

Mark Hahn hahn at physics.mcmaster.ca
Mon Oct 1 12:25:40 EDT 2001


> > > Do you know if it is currently possible to have diskless nodes
> > > having their swap over the network ?
> >
> > omitting swap is usually a bad idea, since various revisions of the VM
> > have been unstable in the absence of swap - they used swapcache 
> > allocation as a book-keeping aid, and didn't necessarily generate 
> > any swap *traffic*.
> 
> I believe that you are referring to the 2.4 kernels with the reference
> to kernels that are unstable without swap.  The 2.2 kernels perform
> better with even a little bit of swap, but they don't require swap space.

yes.  it's clear, though, that swap is basically always a good 
thing to have, which is why VM designers always consider that 
the norm.  (that is, Linux is designed to operate with swap,
and when swap is full or absent, should ideally still behave fairly
well, but that's an outlier state.)  not having swap is a declaration
that either all your pages are equally active, or you don't mind 
wasting ram on idle dirty pages.  swap allows the VM to optimize the 
use of ram; this could be irrelevant to beowulf apps, but remember
that disk IO is through the page cache as well.

oops, sorry for the soapbox...


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