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SubjectRe: 2.4.8/2.4.9 VM problems
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On August 20, 2001 09:12 pm, Marcelo Tosatti wrote:
> On Mon, 20 Aug 2001, Daniel Phillips wrote:
> > On August 20, 2001 09:14 pm, Mike Galbraith wrote:
> > > We need to get the pages 'actioned' (the only thing that really matters)
> > > off of the dirty list so that they are out of the equation.. that I'm
> > > sure of.
> >
> > Well, except when the page is only going to be used once, or not at all (in
> > the case of an unused readahead page). Otherwise, no, we don't want to have
> > frequently used pages or pages we know nothing about dropping of the inactive
> > queue into the bit-bucket. There's more work to do to make that come true.
>
> Find riel's message with topic "VM tuning" to linux-mm, then take a look
> at the 4th aging option.
>
> That one _should_ be able to make us remove all kinds of "hacks" to do
> drop behind, and also it should keep hot/warm active memory _in cache_
> for more time.

I looked at it yesterday. The problem is, it loses the information about *how*
a page is used: pagecache lookup via readahead has different implications than
actual usage. The other thing that looks a little problematic, which Rik also
pointed out, is the potential long lag before the inactive page is detected.
A lot of IO can take place in this time, filling up the active list with pages
that we could have evicted much earlier.

--
Daniel
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