Re: About the free page pool

[Rik van Riel <riel@conectiva.com.br>]

On Mon, 2 Sep 2002, Andrew Morton wrote:

> > How important is it to maintain a list of free pages?  That is, how
> > critical is it that there be some pool of free pages from which the only
> > bookkeeping required is the removal of that page from the free list.
>
> There are several reasons, all messy.

[snip]

> It's feasible.  It'd take some work.  Probably it would best be implemented
> via a third list.  That list would be protected by an IRQ-safe lock,

I don't think we need to bother with the IRQ-safe part.

It's much simpler if we just do:

1) have a normal free list, but have it smaller ...
   say, between zone->pages_min and zone->pages_low

2) if the free pages drop below the low water mark,
   have either a normal allocator or a kernel thread
   refill it to the high water mark, from the clean
   pages list

3) have the free+clean target set to something higher,
   say zone->pages_high ... we could even tune this
   automatically, if we run out of free+clean pages too
   often kswapd should probably try to keep more pages
   clean

What do you think, would this work?

regards,

Rik
-- 
Bravely reimplemented by the knights who say "NIH".

http://www.surriel.com/		http://distro.conectiva.com/

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