Re: 2.4.23aa2 (bugfixes and important VM improvements for the high end)

[Ingo Molnar]

* Andrea Arcangeli <andrea@xxxxxxx> wrote:

> [...] 8/16/32G boxes works perfectly with 3:1 with the stock 2.4 VM
> (after you nuke rmap).

the mem_map[] on 32G is 400 MB (using the stock 2.4 struct page). This
leaves ~500 MB for the lowmem zone. It's ridiculously easy to use up 500
MB of lowmem. 500 MB is a lowmem:RAM ratio of 1:60. With 4/4 you have 6
times more lowmem. So starting at 32 GB (but often much earlier) the 3/1
split breaks down. And you obviously it's a no-go at 64 GB.

inbetween it all depends on the workload. If the 3:1 split works fine
then sure, use it. There's no one kernel that fits all sizes.

	Ingo
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