swapout frenzy solution

[Rik van Riel <H.H.vanRiel@fys.ruu.nl>]

Hi Linus,

I've just come up with a simple 'solution' for the swapout
frenzy experienced by the recent free_memory_available()
test in kswapd.

We simply stop kswapd when nr_free_pages > free_pages_high * 4.
Since page allocation always assigns a page from the smallest
possible unit, the larger free areas are extremely likely to
grow bigger and bigger, especially when nr_free_pages is very
large, say > 3 * free_pages_high.

Since my vmscan.c is somewhat different from yours, and since
I don't know what you have done to it in the last week, I
won't send you a diff.

(trying to merge a faulty diff is _far_ more work than
doing the 30 second edit yourself :-)

I'm trying it now, and I don't see any swapout frenzies
occurring anymore...

Rik.
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