On Fri, 12 May 2000, Linus Torvalds wrote:
> With such a setup, your patch makes lots of sense - trying to decouple
> the highmem zone as much as possible. But the more recent kernels
> should be better at not touching zones that don't need touching (it
> will still change the LRU information, though).
i initially tested pre7-9 and it showed bad behavior: high kswapd activity
trying to balance highmem, while the pagecache is primarily filled from
the highmem. I dont think this can be fixed without 'silencing'
ZONE_HIGHMEM's balancing activities: the pagecache allocates from highmem
so it puts direct pressure on the highmem zone.
This had two effects: wasted CPU time, but it also limited the
page-cache's maximum size to the size of highmem. I'll try the final
pre7-2.3.99 kernel as well in a minute to make sure. (i think the bad
behavior is still be there, judging from the differences between pre9 and
the final patch.)
(i've attached a patch against final-pre7, which is not complete and which
i'm not yet happy about (the kernel shows bad behavior if lots of dirty
data is generated by many processes), but it shows eg. the highmem.c
cleanup that is possible.)
Ingo
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