On Thu, 19 Aug 2010, Patrick O'Callaghan wrote:
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/
Posted November 28, 2006 by corbet:
If a large ("high order") block of memory is not available
when needed,
something will fail and yet another user will start to consider switching to BSD.
BSD does it differently?
--
Michael hennebry(a)web.cs.ndsu.NoDak.edu
"Pessimist: The glass is half empty.
Optimist: The glass is half full.
Engineer: The glass is twice as big as it needs to be."