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SubjectRe: vm issues (2)
On Tue, Feb 25, 2003 at 01:13:28PM +0100, Dejan Muhamedagic wrote:
> Hello,
>
> The new kernel 2.4.21-pre4aa3 is running now, but the box behaves
> similarly. It still swaps quite a lot and much more than the rmap
> vm. Both servers are under the same load.
>
> One difference is the amount of free memory:
>
> r b w swpd free buff cache si so bi bo in cs us sy id
> aa:
> 0 7 0 5773620 202416 118076 2069716 5330 746 5330 766 4845 5597 12 14 74
> rmap:
> 0 0 0 3498044 13572 4144 4754596 74 0 75 6 642 598 5 3 92
>
> The aa kernel keeps ~200MB out of 6GB of memory unused. I'm not
> sure, but if we could reduce it perhaps there would be much less
> swapping. Is there a way to achieve this?

that is a feature, it guarantees highmem unfreeable allocations like
pagetables can't eat all your normal zone. You can reduce the 200MB with
this boot command:

lower_zone_reserve=256,256

As to decrease the swapping I just told you how to do that tweaking
vm_mapped_ratio.

>
> Another notable difference between the two vm versions is that the
> rmap vm maintains about 80% of memory on the active list and the
> aa vm much less: between 4% and 12%. The rmap vm must use more
> CPU, but these servers have a lot of processing power so it is not
> noticeable.

the theory was that rmap would reduce the cpu utilization but of course
the patch don't do juts rmap.

Andrea
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