better zone and watermark balancing

This patchset I have had around for a long time and improves
various zone and watermark balancing by making calculations
more logical.

When reading 128GB through the pagecache, in 4 concurrent
streams, the final page residency and total reclaim ratios
look like this (no highmem, ~900MB RAM):

2.6.14-git3
DMA pages=  2214, scan= 124146
NRM pages=215966, scan=3990129

      Pages  Scan
DMA  01.01  03.01
NRM  98.99  96.99


2.6.14-git3-vm
DMA pages=  2220, scan=  99264
NRM pages=216373, scan=4011975

      Pages  Scan
DMA  01.01  02.41
NRM  98.99  97.59

So in this case, DMA is still getting a beating, but things have
improved nicely. Now are results with highmem and ~4GB RAM:

2.6.14-git3
DMA pages=0, scan=0
NRM pages=177241, scan=1607991
HIG pages=817122, scan=1607166

     Pages  Scan
DMA 00.00  00.00
NRM 17.83  50.01
HIG 82.17  49.99

2.6.14-git3-vm
DMA pages=0, scan=0
NRM pages=178215, scan=553311
HIG pages=815771, scan=2757744

     Pages  Scan
DMA 00.00  00.00
NRM 17.92  16.71
HIG 82.07  83.28

Current kernels are abysmal, while the patches bring scanning to
an almost perfect ratio.

-- 
SUSE Labs, Novell Inc.

Send instant messages to your online friends http://au.messenger.yahoo.com