Re: [RFC][PATCH 0/3] beat kswapd with the proverbial clue-bat

Arjan van de Ven
2004-09-05T18:41:46Z

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On Sun, Sep 05, 2004 at 10:58:07AM -0700, Linus Torvalds wrote:
>
>
> On Sun, 5 Sep 2004, Arjan van de Ven wrote:
> >
> > well... we have a reverse mapping now. What is stopping us from doing
> > physical defragmentation ?
>
> Nothing but replacement policy, really, and the fact that not everything
> is rmappable.
>
> I think we should _normally_ honor replacement policy, the way we do now.

yes it absolutely is quite a heavy hammer.
However right now the alternative (free a LOT of memory and hope it
collapses into higher order ones) is even heavier, freeing the wrong 8 pages
is less of a disturbance than freeing 8000 of the mostly wrong pages ;)

I absolutely agree this heavy hammer only should trigger if there is a
request for a higher order page that isn't there. Doing it from a special
thread does make sense, makes it relatively easy to keep track of such
wakeups and more importantly rate limit them etc.

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