MM patches (was Re: why swap at all?)

[Nick Piggin]

Denis Vlasenko wrote:

> (pages with program/library code, data of e.g. your Mozilla, etc),
> please submit a report to lkml. VM gurus said more than once
> that they _want_ to fix things, but need to know how to reproduce.

Yep.

Thanks to everyone's input I was able to test and adapt my mm work.
It is hopefully at a stage where it can have wider testing now. It
is stable on my SMP system under very heavy swapping, but the usual
caution applies.

Test is 4 x cat 8GB > /dev/null (aggregate 100-200MB/s!) while in X,
with xterms and mozilla open browsing and grepping kernel tree, etc.

Plain 2.6.7-rc1-mm1 swapped 200MB then completely froze up the system
within 9 seconds of starting the read load. Things remained fairly
responsive with my patch applied. A bit of swap out, but very little
swap in, which is good. The entire 32GB went through the pagecache no
problem.

A couple of concurrent mkisofs's writing 4 GB isos don't seem to be
any problem either with the patched kernel. Haven't tried plain -mm
yet.

http://www.kerneltrap.org/~npiggin/nickvm-267r1m1.gz

It is a cocktail of cleanups, simplification, and enhancements. The
main ones that applie here is my split active lists patch (search
archives for details), and explicit use-once logic.

Known issue: page reclaim can get a little bit lumpy (ie lots of
memory freed up at once), but that is just a matter of teaching
things not to bite off massive chunks at a time when it starts
hitting memory pressure.
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