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RE: Virtual Memory

From: Kevin Closson <kevinc_at_polyserve.com>
Date: Fri, 25 Aug 2006 12:07:16 -0700
Message-ID: <5D2570CAFC98974F9B6A759D1C74BAD0E5AE0B@ex2.ms.polyserve.com>

 >>>

>>>A decent OS shouldn't start paging much before it starts
>>>running out of physical memory,

...well, there is a difference between paging and allocating swap in the event paging is required. The jury is out on OSes that allocate swap only at the point when some major page faults or process swaps (same mechanisms usually) need to occur. If there doesn't happen to be enough swap space when such an on-demand allocation takes place, the only resort for the OS is to start killing "stuff"... what "stuff" is best to kill?

Way beck when, there were Unix derivations that didn't like this idea so they allocated swap within the page allocation code so there would never be a desperation swap failure... if a process has a page, there is a page in swap behind it.

I never could grasp the idea of just picking a process and killing it because the system is low on swap...especially since the best candidate to kill is one that has a significant amount of virtual memory...

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Received on Fri Aug 25 2006 - 14:07:16 CDT

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