Re: pre8: where has the anti-hog code gone?

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

On Sun, 14 May 2000, Ingo Molnar wrote:

> this seems to have done the trick here - no more NULL gfps. Any
> better generic suggestion than the explicit 'page transport'
> path between freeing and allocation points?

Mark the zone as a "steal-before-allocate" zone while
one user process is in the page stealer because it
could not find an easy page.

if (couldn't find an easy page) {
	atomic_inc(&zone->steal_before_allocate);
	try_to_free_pages();
	blah blah blah;
	atomic_dec(&zone->steal_before_allocate);
}

And the allocation path can be changed to always call
try_to_free_pages() if zone->steal_before_allocate is
set.

This way we won't just guarantee that we can keep the page
we just freed, but also that _other_ processes won't get
false hopes and/or run out of memory. Furthermore, by going
into try_to_free_pages() a bit more agressively we could
reduce memory fragmentation a bit (but I'm not sure if this
effect would be significant or not).

Rik
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