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Re: [K12OSN] KX7-333R mboard for Athalon Server / Swap Death?



Also remember that most apps contain some percentage of code that gets
run only very rarely (if at all), like init time code.  This code is
perfectly happy to move to swap and make space for more important
stuff.

So swap is not a bad thing at all, and it may provide you with more
usable RAM space than you would otherwise have with essential no
performance degradation.  Just make sure that you have enough RAM
to handle the "active" memory requirements.  Perhaps the only way
to determine that is to watch the stats on swap activity (the amount
of swap used is irrelevant, the important thing is how often pages
are being swapped.)

-Don

chip wrote:
> 
> > If swap hampers a system THAT badly - seems like it would be desirable
> > to DISABLE swap space after packing a large ammount of RAM into the
> > system - say 128-256mb/Client.  That gets expensive of course, but words
> > such as "out of the game" and "kill a setup" (someone else used) make it
> > sound like an unrecoverable crawl.
> 
> I would not recommend disabling swap for the vast majority of situations.
> Think of it this way -- RAM is measured in Nano Seconds(for example 5.5ns
> SDRAM), while Hard Drive SEEK time is measured in Milli Seconds(and that is
> seek time, not read time).  Swap is a good thing, don't underestimate it,
> but I would never count on it as something to rely upon for speed, but it is
> very nice to have it when speed might not matter -- but keeping the kernel
> from panicking and killing processes does matter.
> 
> What I am trying to say for a LTSP type environment, to rely upon swap just
> adds more latency to every action on the clients, but with Hard Drives so
> cheap there isn't a problem with adding in 200+ Mb of Swap for Emergencies.
> 
> > Couldn't the clients just close some
> > apps to free up RAM if they get into a swap situation?
> Yes, when clients exit apps it should free up RAM.
> 
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-- 
Don Christensen       Senior Software Development Engineer
djc cisco com         Cisco Systems, Santa Cruz, CA
  "It was a new day yesterday, but it's an old day now."





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