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SubjectRe: Kernel profile
On Wed, 31 Jul 1996, Gonzalo Tornaria wrote:

> DUPRE Christophe <duprec@jsp.umontreal.ca> wrote:
>
> > Excuse for talking before checking the code, but I think two
> > lists would be simpler and probably faster...
>
> > With one list, your "scavenger" need to walk the list, and when
> > it finds a non-zeroed structure, it needs to zero it then move it
> > to the front of the list. If you have two lists, scavenger only
> > takes the first of the non-zeroed list, zero it then puts it at
> > the front of the second list, no walking necessary.
>
> > Secondly, with only one list, you need a way to check if the
> > structure has been zeroed or not - either add a flag to the
> > structure, or re-use an already there flag... Either way, it's a
> > flag that needs to be checked then cleared when a process needs
> > to allocate a structure.
>
> > So the one-list solution might use a bit more memory (though not
> > much), add a flag clear, and slow down the "scavenger" in it's
> > job because it needs to walk the list.
>
> You can do with one list. Take zeroed structures from the head, and put used
> non-zeroed structures at the end. You just need a pointer to the first
> non-zeroed structure in the list, so the "scavenger" knows where to start
> zeroing, and you can check whether you are out of zeroed structures. Or you can
> add non-zeroed after the first non-zeroed (so you don't need a pointer to the
> end).

Excuse me, but what you are describing is a two-lists solution, with the
last element of the first list pointing to the first element of the second
list, a link that will never be followed anyway because we never walk the
list...

Christophe Dupre Universite de Montreal
Internet: duprec@jsp.umontreal.ca Qc, Canada
Montreal, Qc, Canada
"Nous ne sommes pas libres de ne pas etre libres, nous sommes obliges de
l'etre" - Fernando Savater

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