[PATCH 0/6] Use two zonelists per node instead of multiple zonelists v11r2

[Mel Gorman <mel@csn.ul.ie>]

This is a rebase of the two-zonelist patchset to 2.6.24-rc4-mm1 and some
warnings cleared up. The warnings were not picked up before as they were
introduced early in the set and cleared up by the end. This might have hurt
bisecting so were worth fixing even if the end result was correct. Tests
looked good, both numactltest (slightly modified) and performance tests.

I believe Lee has been testing heavily with a version of the patchset
almost identical to this and hasn't complained. If Lee is happy enough,
can you merge these to -mm for wider testing please Andrew?

Changelog since V10
  o Rebase to 2.6.24-rc4-mm1
  o Clear up warnings in fs/buffer.c early in the patchset

Changelog since V9
  o Rebase to 2.6.24-rc2-mm1
  o Lookup the nodemask for each allocator callsite in mempolicy.c
  o Update NUMA statistics based on preferred zone, not first zonelist entry
  o When __GFP_THISNODE is specified with MPOL_BIND and the current node is
    not in the allowed nodemask, the first node in the mask will be used
  o Stick with using two zonelists instead of one because of excessive
    complexity with corner cases

Changelog since V8
  o Rebase to 2.6.24-rc2
  o Added ack for the OOM changes
  o Behave correctly when GFP_THISNODE and a node ID are specified
  o Clear up warning over type of nodes_intersects() function

Changelog since V7
  o Rebase to 2.6.23-rc8-mm2

Changelog since V6
  o Fix build bug in relation to memory controller combined with one-zonelist
  o Use while() instead of a stupid looking for()
  o Instead of encoding zone index information in a pointer, this version
    introduces a structure that stores a zone pointer and its index 

Changelog since V5
  o Rebase to 2.6.23-rc4-mm1
  o Drop patch that replaces inline functions with macros

Changelog since V4
  o Rebase to -mm kernel. Host of memoryless patches collisions dealt with
  o Do not call wakeup_kswapd() for every zone in a zonelist
  o Dropped the FASTCALL removal
  o Have cursor in iterator advance earlier
  o Use nodes_and in cpuset_nodes_valid_mems_allowed()
  o Use defines instead of inlines, noticably better performance on gcc-3.4
    No difference on later compilers such as gcc 4.1
  o Dropped gfp_skip patch until it is proven to be of benefit. Tests are
    currently inconclusive but it definitly consumes at least one cache
    line

Changelog since V3
  o Fix compile error in the parisc change
  o Calculate gfp_zone only once in __alloc_pages
  o Calculate classzone_idx properly in get_page_from_freelist
  o Alter check so that zone id embedded may still be used on UP
  o Use Kamezawa-sans suggestion for skipping zones in zonelist
  o Add __alloc_pages_nodemask() to filter zonelist based on a nodemask. This
    removes the need for MPOL_BIND to have a custom zonelist
  o Move zonelist iterators and helpers to mm.h
  o Change _zones from struct zone * to unsigned long
  
Changelog since V2
  o shrink_zones() uses zonelist instead of zonelist->zones
  o hugetlb uses zonelist iterator
  o zone_idx information is embedded in zonelist pointers
  o replace NODE_DATA(nid)->node_zonelist with node_zonelist(nid)

Changelog since V1
  o Break up the patch into 3 patches
  o Introduce iterators for zonelists
  o Performance regression test

The following patches replace multiple zonelists per node with two zonelists
that are filtered based on the GFP flags. The patches as a set fix a bug
with regard to the use of MPOL_BIND and ZONE_MOVABLE. With this patchset,
the MPOL_BIND will apply to the two highest zones when the highest zone
is ZONE_MOVABLE. This should be considered as an alternative fix for the
MPOL_BIND+ZONE_MOVABLE in 2.6.23 to the previously discussed hack that
filters only custom zonelists.

The first patch cleans up an inconsitency where direct reclaim uses
zonelist->zones where other places use zonelist.

The second patch introduces a helper function node_zonelist() for looking
up the appropriate zonelist for a GFP mask which simplifies patches later
in the set.

The third patch replaces multiple zonelists with two zonelists that are
filtered. The two zonelists are due to the fact that the memoryless patchset
introduces a second set of zonelists for __GFP_THISNODE.

The fourth patch introduces helper macros for retrieving the zone and node indices of entries in a zonelist.

The final patch introduces filtering of the zonelists based on a nodemask. Two
zonelists exist per node, one for normal allocations and one for __GFP_THISNODE.

Performance results varied depending on the machine configuration. In real
workloads the gain/loss will depend on how much the userspace portion of
the benchmark benefits from having more cache available due to reduced
referencing of zonelists.

These are the range of performance losses/gains when running against
2.6.24-rc4-mm1. The set and these machines are a mix of i386, x86_64 and
ppc64 both NUMA and non-NUMA.

			     loss   to  gain
Total CPU time on Kernbench: -0.86% to  1.13%
Elapsed   time on Kernbench: -0.79% to  0.76%
page_test from aim9:         -4.37% to  0.79%
brk_test  from aim9:         -0.71% to  4.07%
fork_test from aim9:         -1.84% to  4.60%
exec_test from aim9:         -0.71% to  1.08%

-- 
Mel Gorman
Part-time Phd Student                          Linux Technology Center
University of Limerick                         IBM Dublin Software Lab
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