Is swap really needed when RAM's aplenty

Patrick O'Callaghan pocallaghan at gmail.com
Thu Aug 19 14:33:13 UTC 2010


On Thu, 2010-08-19 at 09:22 -0500, Michael Hennebry wrote:
> On Thu, 19 Aug 2010, Gregory Hosler wrote:
> 
> > If the memory gets fragged and the kernel wants to defrag, e.g. for a memory
> > request from an application, in order to defrag any "dirty" data portions (those
> > pages that have been written to), the kernel *requires* there to be swap.
> > Otherwise there is no place to write the dirty pages out, in order to read them
> > in elsewhere.
> 
> I didn't realize that memory could get fragged.
> I'd thought that one reason for virtual memory
> was allowing pages to be renumbered at will,
> the kernel's will, of course.

I thought so too, but see: http://lwn.net/Articles/211505/

poc



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