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SubjectRe: VM Requirement Document - v0.0
On Tue, 3 Jul 2001, Daniel Phillips wrote:

> On Monday 02 July 2001 20:42, Rik van Riel wrote:
> > On Thu, 28 Jun 2001, Marco Colombo wrote:
> > > I'm not sure that, in general, recent pages with only one access are
> > > still better eviction candidates compared to 8 hours old pages. Here
> > > we need either another way to detect one-shot activity (like the one
> > > performed by updatedb),
> >
> > Fully agreed, but there is one problem with this idea.
> > Suppose you have a maximum of 20% of your RAM for these
> > "one-shot" things, now how are you going to be able to
> > page in an application with a working set of, say, 25%
> > the size of RAM ?
>
> Easy. What's the definition of working set? Those pages that are frequently
> referenced. So as the application starts up some of its pages will get
> promoted from used-once to used-often. (On the other hand, the target
> behavior here conflicts with the goal of grouping together several
> temporally-related accesses to the same page together as one access, so
> there's a subtle distinction to be made here, see below.)
[...]

In Rik example, the ws is larger than available memory. Part of it
(the "hottest" one) will get double-accesses, but other pages will keep
condending the few available (physical) pages with no chance of being
accessed twice. But see my previous posting...

.TM.
--
____/ ____/ /
/ / / Marco Colombo
___/ ___ / / Technical Manager
/ / / ESI s.r.l.
_____/ _____/ _/ Colombo@ESI.it

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