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SubjectRe: Elevator problems began at... 2.3.FORTY-THREE-pre7 to be exact :)


On Thu, 2 Mar 2000, Lawrence Manning wrote:
> >
> > You meant 2.3.43-6 and 2.3.43-7, right?
>
> Sorry, yes! The patches between 2.3.42 and 2.3.43! The uname is still
> 2.3.42, so I got confused :( oops, sorry for confusion folks!! Won't
> happen again :) Its first time I've looked at pre patches...

Thanks for hunting it down, though. The 6-7 is one of the bigger jumps,
but it does contain a few rather suggestive things.

In particular, pre-6-7 is where the per-zone balancing thing went in.. And
I think I see something really strange: the "pages_min/low/high" stuff is
per-zone, but the zone size requirements are calculated with some really
strange calculations based off the _cumulative_ size of the zones as they
are added.

Kanoj, I think that was your change. Would you mind looking at

free_area_init_core()

and explaining the logic behind the

zone->pages_min = mask;
zone->pages_low = mask*2;
zone->pages_high = mask*3;

calculations (or if no logic to them, which is my suspicion, then maybe
come up with a fix ;).

Using a cumulative number and it's ratio just can't be right. And getting
these numbers wrong will make kswapd try to page out some zone much more
aggressively than it should, so it would explain dbench performance going
down..

Linus


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