Re: [Bug 890] New: performance regression compared to 2.4.20 under tight RAM conditions

From: Andrew Morton (
Date: Tue Jul 08 2003 - 13:20:48 EST

"Martin J. Bligh" <> wrote:
> As can be seen, the differences are quite significant, about three seconds on
> average, which I believe may be related to the increased swapping time I have
> encountered.

The 2.4 VM's virtual scan has the effect of swapping out one process at a
time. 2.5's physical(ish) scan doesn't have that side-effect.

It means that in 2.4, the lucky processes can make decent progress. In
2.5, everyone makes equal progress and everyone thrashes everyone else to

To fix this properly we need load control: to identify when the system is
thrashing and to explicitly suspend chosen processes for a while, so other
processes can make decent progress. A couple of people are looking at
that; I'm not sure what stage it is at.

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