This patch implements a kswapd process for each memory zone.  The original code 
came from Bill Irwin, but the current VM is quite a bit different from the one 
that he wrote it for, so not much remains.  The current kswapd interface is much 
more simple than before because there is a single waitqueue and there is a 
single place where it is emptied.

kswapd_can_sleep() and kswapd_balance() are simpler now that the extra pgdat 
level of indirection is gone.

Tested on 8-way PIII with highmem off and then 4GB support.  With 4GB support, I 
did 20 parallel greps through a 10GB fileset while some other processes 
allocated and freed 1-2GB chunks of memory.  That gave kswapd a good workout, 
and I observed it running the zone Highmem and zone Normal kswapd threads.  So, 
it survives my torture test.  It also removes more code than it adds.

include/linux/mmzone.h |    2 +
include/linux/swap.h   |    1
mm/page_alloc.c        |   11 +++++-
mm/vmscan.c            |   88 +++++++++++++++++--------------------------------
4 files changed, 42 insertions(+), 60 deletions(-)

-- 
Dave Hansen
haveblue@us.ibm.com