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

[Nick Piggin <piggin@cyberone.com.au>]

Rik van Riel wrote:

>On Mon, 15 Mar 2004, Andrea Arcangeli wrote:
>
>
>>it is the absolutely worst case since both lru could be of around the same
>>size (800M zone-normal-lru and 1.2G zone-highmem-lru), maximizing the
>>loss of "age" information needed for optimal reclaim decisions.
>>
>
>You only lose age information if you don't put equal aging
>pressure on both zones.  If you make sure the allocation and
>pageout pressure are more or less in line with the zone sizes,
>why would you lose any aging information ?
>
>

I can't see that you would, no. But maybe I've missed something.
We apply pressure equally except when there is a shortage in a
low memory zone, in which case we can scan only the required
zone(s).

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.