Re: why swap at all?

[Bill Davidsen <davidsen@tmr.com>]

William Lee Irwin III wrote:
> On Thu, May 27, 2004 at 08:31:26AM -0400, Piszcz, Justin Michael wrote:
> 
>>If I have 16GB of ram should I use swap?
>>Would swap cause the machine to slow down?
> 
> 
> Yes. You want swap so you can physically relocate anonymous pages in the
> rare case one ends up somewhere it could cause memory pressure against
> allocations that can only be satisfied by a restricted range of memory.

It would seem that the o/s has enough information to separate pages into 
  categories such as 'part of a program,' 'unwritten user write() data,' 
'user read() data sequential," 'user read data random' (read after seek) 
and the like. It would be nice if admins could do tuning on how the o/s 
weights giving these memory. The swappiness tuner is certainly a start, 
in practice it does help with atypical loads.

And Nick's latest stuff against 2.6.7-rc1-mm1 certainly seems to work 
very well on my little 96MB slow box with a few dozen windows open. I 
would call it the best I've run on this box, ever.


-- 
    -bill davidsen (davidsen@tmr.com)
"The secret to procrastination is to put things off until the
  last possible moment - but no longer"  -me