Re: [2.4] heavy-load under swap space shortage

From: Nick Piggin
Date: Mon Mar 15 2004 - 17:10:03 EST

Andrea Arcangeli wrote:

On Tue, Mar 16, 2004 at 01:37:04AM +1100, Nick Piggin wrote:

This case I think is well worth the unfairness it causes, because it
means your zone's pages can be freed quickly and without freeing pages
from other zones.

freeing pages from other zones is perfectly fine, the classzone design
gets it right, you have to free memory from the other zones too or you
have no way to work on a 1G machine. you call the thing "unfair" when it
has nothing to do with fariness, your unfariness is the slowdown I
pointed out, it's all about being able to maintain a more reliable cache
information from the point of view of the pagecache users (the pagecache
users cares at the _classzone_, they can't care about the zones
themself), it has nothing to do with fairness.

What I meant by unfairness is that low zone scanning in response
to low zone pressure will not put any pressure on higher zones.
Thus pages in higher zones have an advantage.

We do scan lowmem in response to highmem pressure.

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