Memory upgrade and swap partition size

Ben Scott dragonhawk at gmail.com
Tue Sep 26 23:22:01 EDT 2006


On 9/26/06, Bill Sconce <sconce at in-spec-inc.com> wrote:
> One morning after a sufficient number of cups of coffee it dawned on me what
> was wrong:  that the "2X" rule was fatal for a 384MB machine and my greedy
> use of Firefox tabs.  I took a deep breath, wiped the disk, created a 2GB
> swap file and reinstalled.  It NEVER stalls now -- the first week or so I
> had to keep pinching myself how well the poor thing worked with "enough"
> memory at last.

  Very interesting.  I'd never tried that approach to that extreme
before.  I'll keep this in mind the next time I'm working with an old
machine.  Thanks for the info.

> And how dumb I'd been to ever credit "2X".  An old wives' tale...

  From what I remember, there was a time where this number wasn't
arbitrary, but rather, had something to do with how memory management
was implemented in the Linux kernel.  (Details I have forgotten, if I
ever knew them.)  This "rule of thumb" dates back to at least 2.2,
possibly 2.0.  The memory manager in 2.6 has practically no
resemblance to the one in 2.0, or so I understand.  So the old rules
are no longer valid.

  There's a lesson here: The square of the hypotenuse..., er, wait,
no, wrong lesson.  The lesson is... hmmm, come to think of it, there
are actually two lessons--er, I'll come in again.

  There are two lessons here: (1) Rules are only valid for as long as
their preconditions remain unchanged.  (2) "Common knowledge" is
commonly wrong.

-- Ben



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