1. 01 7月, 2006 1 次提交
    • C
      [PATCH] zoned vm counters: basic ZVC (zoned vm counter) implementation · 2244b95a
      Christoph Lameter 提交于
      Per zone counter infrastructure
      
      The counters that we currently have for the VM are split per processor.  The
      processor however has not much to do with the zone these pages belong to.  We
      cannot tell f.e.  how many ZONE_DMA pages are dirty.
      
      So we are blind to potentially inbalances in the usage of memory in various
      zones.  F.e.  in a NUMA system we cannot tell how many pages are dirty on a
      particular node.  If we knew then we could put measures into the VM to balance
      the use of memory between different zones and different nodes in a NUMA
      system.  For example it would be possible to limit the dirty pages per node so
      that fast local memory is kept available even if a process is dirtying huge
      amounts of pages.
      
      Another example is zone reclaim.  We do not know how many unmapped pages exist
      per zone.  So we just have to try to reclaim.  If it is not working then we
      pause and try again later.  It would be better if we knew when it makes sense
      to reclaim unmapped pages from a zone.  This patchset allows the determination
      of the number of unmapped pages per zone.  We can remove the zone reclaim
      interval with the counters introduced here.
      
      Futhermore the ability to have various usage statistics available will allow
      the development of new NUMA balancing algorithms that may be able to improve
      the decision making in the scheduler of when to move a process to another node
      and hopefully will also enable automatic page migration through a user space
      program that can analyse the memory load distribution and then rebalance
      memory use in order to increase performance.
      
      The counter framework here implements differential counters for each processor
      in struct zone.  The differential counters are consolidated when a threshold
      is exceeded (like done in the current implementation for nr_pageache), when
      slab reaping occurs or when a consolidation function is called.
      
      Consolidation uses atomic operations and accumulates counters per zone in the
      zone structure and also globally in the vm_stat array.  VM functions can
      access the counts by simply indexing a global or zone specific array.
      
      The arrangement of counters in an array also simplifies processing when output
      has to be generated for /proc/*.
      
      Counters can be updated by calling inc/dec_zone_page_state or
      _inc/dec_zone_page_state analogous to *_page_state.  The second group of
      functions can be called if it is known that interrupts are disabled.
      
      Special optimized increment and decrement functions are provided.  These can
      avoid certain checks and use increment or decrement instructions that an
      architecture may provide.
      
      We also add a new CONFIG_DMA_IS_NORMAL that signifies that an architecture can
      do DMA to all memory and therefore ZONE_NORMAL will not be populated.  This is
      only currently set for IA64 SGI SN2 and currently only affects
      node_page_state().  In the best case node_page_state can be reduced to
      retrieving a single counter for the one zone on the node.
      
      [akpm@osdl.org: cleanups]
      [akpm@osdl.org: export vm_stat[] for filesystems]
      Signed-off-by: NChristoph Lameter <clameter@sgi.com>
      Cc: Trond Myklebust <trond.myklebust@fys.uio.no>
      Signed-off-by: NAndrew Morton <akpm@osdl.org>
      Signed-off-by: NLinus Torvalds <torvalds@osdl.org>
      2244b95a
  2. 23 6月, 2006 3 次提交
  3. 06 6月, 2006 1 次提交
    • R
      [PATCH] Sparsemem build fix · 93ff66bf
      Ralf Baechle 提交于
      From: Ralf Baechle <ralf@linux-mips.org>
      
      <linux/mmzone.h> uses PAGE_SIZE, PAGE_SHIFT from <asm/page.h> without
      including that header itself.  For some sparsemem configurations this may
      result in build errors like:
      
        CC      init/initramfs.o
      In file included from include/linux/gfp.h:4,
                       from include/linux/slab.h:15,
                       from include/linux/percpu.h:4,
                       from include/linux/rcupdate.h:41,
                       from include/linux/dcache.h:10,
                       from include/linux/fs.h:226,
                       from init/initramfs.c:2:
      include/linux/mmzone.h:498:22: warning: "PAGE_SHIFT" is not defined
      In file included from include/linux/gfp.h:4,
                       from include/linux/slab.h:15,
                       from include/linux/percpu.h:4,
                       from include/linux/rcupdate.h:41,
                       from include/linux/dcache.h:10,
                       from include/linux/fs.h:226,
                       from init/initramfs.c:2:
      include/linux/mmzone.h:526: error: `PAGE_SIZE' undeclared here (not in a function)
      include/linux/mmzone.h: In function `__pfn_to_section':
      include/linux/mmzone.h:573: error: `PAGE_SHIFT' undeclared (first use in this function)
      include/linux/mmzone.h:573: error: (Each undeclared identifier is reported only once
      include/linux/mmzone.h:573: error: for each function it appears in.)
      include/linux/mmzone.h: In function `pfn_valid':
      include/linux/mmzone.h:578: error: `PAGE_SHIFT' undeclared (first use in this function)
      make[1]: *** [init/initramfs.o] Error 1
      make: *** [init] Error 2
      Signed-off-by: NRalf Baechle <ralf@linux-mips.org>
      Seems-reasonable-to: Andy Whitcroft <apw@shadowen.org>
      Signed-off-by: NAndrew Morton <akpm@osdl.org>
      Signed-off-by: NLinus Torvalds <torvalds@osdl.org>
      93ff66bf
  4. 22 5月, 2006 1 次提交
    • B
      [PATCH] Align the node_mem_map endpoints to a MAX_ORDER boundary · e984bb43
      Bob Picco 提交于
      Andy added code to buddy allocator which does not require the zone's
      endpoints to be aligned to MAX_ORDER.  An issue is that the buddy allocator
      requires the node_mem_map's endpoints to be MAX_ORDER aligned.  Otherwise
      __page_find_buddy could compute a buddy not in node_mem_map for partial
      MAX_ORDER regions at zone's endpoints.  page_is_buddy will detect that
      these pages at endpoints are not PG_buddy (they were zeroed out by bootmem
      allocator and not part of zone).  Of course the negative here is we could
      waste a little memory but the positive is eliminating all the old checks
      for zone boundary conditions.
      
      SPARSEMEM won't encounter this issue because of MAX_ORDER size constraint
      when SPARSEMEM is configured.  ia64 VIRTUAL_MEM_MAP doesn't need the logic
      either because the holes and endpoints are handled differently.  This
      leaves checking alloc_remap and other arches which privately allocate for
      node_mem_map.
      Signed-off-by: NBob Picco <bob.picco@hp.com>
      Acked-by: NMel Gorman <mel@csn.ul.ie>
      Cc: Dave Hansen <haveblue@us.ibm.com>
      Cc: Andy Whitcroft <apw@shadowen.org>
      Signed-off-by: NAndrew Morton <akpm@osdl.org>
      Signed-off-by: NLinus Torvalds <torvalds@osdl.org>
      e984bb43
  5. 26 4月, 2006 1 次提交
  6. 28 3月, 2006 5 次提交
    • K
      [PATCH] uninline zone helpers · 95144c78
      KAMEZAWA Hiroyuki 提交于
      Helper functions for for_each_online_pgdat/for_each_zone look too big to be
      inlined.  Speed of these helper macro itself is not very important.  (inner
      loops are tend to do more work than this)
      
      This patch make helper function to be out-of-lined.
      
      	inline		out-of-line
      .text   005c0680        005bf6a0
      
      005c0680 - 005bf6a0 = FE0 = 4Kbytes.
      Signed-off-by: NKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
      Signed-off-by: NAndrew Morton <akpm@osdl.org>
      Signed-off-by: NLinus Torvalds <torvalds@osdl.org>
      95144c78
    • K
      [PATCH] for_each_online_pgdat: remove pgdat_list · ae0f15fb
      KAMEZAWA Hiroyuki 提交于
      By using for_each_online_pgdat(), pgdat_list is not necessary now.  This patch
      removes it.
      Signed-off-by: NKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
      Signed-off-by: NAndrew Morton <akpm@osdl.org>
      Signed-off-by: NLinus Torvalds <torvalds@osdl.org>
      ae0f15fb
    • K
      [PATCH] define for_each_online_pgdat · 8357f869
      KAMEZAWA Hiroyuki 提交于
      This patch defines for_each_online_pgdat() as a replacement of
      for_each_pgdat()
      
      Now, online nodes are managed by node_online_map.  But for_each_pgdat()
      uses pgdat_link to iterate over all nodes(pgdat).  This means management
      structure for online pgdat is duplicated.
      
      I think using node_online_map for for_each_pgdat() is simple and sane
      rather ather than pgdat_link.  New macro is named as
      for_each_online_pgdat().  Following patch will fix callers of
      for_each_pgdat().
      
      The bootmem allocater uses for_each_pgdat() before pgdat initialization.  I
      don't think it's sane.  Following patch will fix it.
      Signed-off-by: NYasunori Goto     <y-goto@jp.fujitsu.com>
      Signed-off-by: NKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
      Signed-off-by: NAndrew Morton <akpm@osdl.org>
      Signed-off-by: NLinus Torvalds <torvalds@osdl.org>
      8357f869
    • K
      [PATCH] remove zone_mem_map · a0140c1d
      KAMEZAWA Hiroyuki 提交于
      This patch removes zone_mem_map.
      
      pfn_to_page uses pgdat, page_to_pfn uses zone.  page_to_pfn can use pgdat
      instead of zone, which is only one user of zone_mem_map.  By modifing it,
      we can remove zone_mem_map.
      Signed-off-by: NKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
      Cc: Dave Hansen <haveblue@us.ibm.com>
      Cc: Christoph Lameter <christoph@lameter.com>
      Signed-off-by: NAndrew Morton <akpm@osdl.org>
      Signed-off-by: NLinus Torvalds <torvalds@osdl.org>
      a0140c1d
    • K
      [PATCH] unify pfn_to_page: generic functions · a117e66e
      KAMEZAWA Hiroyuki 提交于
      There are 3 memory models, FLATMEM, DISCONTIGMEM, SPARSEMEM.
      Each arch has its own page_to_pfn(), pfn_to_page() for each models.
      But most of them can use the same arithmetic.
      
      This patch adds asm-generic/memory_model.h, which includes generic
      page_to_pfn(), pfn_to_page() definitions for each memory model.
      
      When CONFIG_OUT_OF_LINE_PFN_TO_PAGE=y, out-of-line functions are
      used instead of macro. This is enabled by some archs and  reduces
      text size.
      Signed-off-by: NKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
      Cc: Hugh Dickins <hugh@veritas.com>
      Cc: Andi Kleen <ak@muc.de>
      Cc: Paul Mackerras <paulus@samba.org>
      Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
      Cc: Richard Henderson <rth@twiddle.net>
      Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
      Cc: Russell King <rmk@arm.linux.org.uk>
      Cc: Ian Molton <spyro@f2s.com>
      Cc: Mikael Starvik <starvik@axis.com>
      Cc: David Howells <dhowells@redhat.com>
      Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
      Cc: Hirokazu Takata <takata.hirokazu@renesas.com>
      Cc: Ralf Baechle <ralf@linux-mips.org>
      Cc: Kyle McMartin <kyle@mcmartin.ca>
      Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
      Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
      Cc: Paul Mundt <lethal@linux-sh.org>
      Cc: Kazumoto Kojima <kkojima@rr.iij4u.or.jp>
      Cc: Richard Curnow <rc@rc0.org.uk>
      Cc: William Lee Irwin III <wli@holomorphy.com>
      Cc: "David S. Miller" <davem@davemloft.net>
      Cc: Jeff Dike <jdike@addtoit.com>
      Cc: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
      Cc: Miles Bader <uclinux-v850@lsi.nec.co.jp>
      Cc: Chris Zankel <chris@zankel.net>
      Cc: "Luck, Tony" <tony.luck@intel.com>
      Signed-off-by: NAndrew Morton <akpm@osdl.org>
      Signed-off-by: NLinus Torvalds <torvalds@osdl.org>
      a117e66e
  7. 02 2月, 2006 2 次提交
  8. 19 1月, 2006 1 次提交
  9. 12 1月, 2006 1 次提交
  10. 09 1月, 2006 2 次提交
  11. 07 1月, 2006 8 次提交
  12. 23 11月, 2005 1 次提交
    • L
      Fix up GFP_ZONEMASK for GFP_DMA32 usage · ac3461ad
      Linus Torvalds 提交于
      There was some confusion about the different zone usage, this should fix
      up the resulting mess in the GFP zonemask handling.
      
      The different zone usage is still confusing (it's very easy to mix up
      the individual zone numbers with the GFP zone _list_ numbers), so we
      might want to clean up some of this in the future, but in the meantime
      this should fix the actual problems.
      Acked-by: NAndi Kleen <ak@suse.de>
      Signed-off-by: NLinus Torvalds <torvalds@osdl.org>
      ac3461ad
  13. 15 11月, 2005 3 次提交
    • A
      [PATCH] x86_64: Speed up numa_node_id by putting it directly into the PDA · 69d81fcd
      Andi Kleen 提交于
      Not go from the CPU number to an mapping array.
      Mode number is often used now in fast paths.
      
      This also adds a generic numa_node_id to all the topology includes
      
      Suggested by Eric Dumazet
      Signed-off-by: NAndi Kleen <ak@suse.de>
      Signed-off-by: NLinus Torvalds <torvalds@osdl.org>
      69d81fcd
    • A
      [PATCH] x86_64: Remove obsolete ARCH_HAS_ATOMIC_UNSIGNED and page_flags_t · 07808b74
      Andi Kleen 提交于
      Has been introduced for x86-64 at some point to save memory
      in struct page, but has been obsolete for some time. Just
      remove it.
      Signed-off-by: NAndi Kleen <ak@suse.de>
      Signed-off-by: NLinus Torvalds <torvalds@osdl.org>
      07808b74
    • A
      [PATCH] x86_64: Add 4GB DMA32 zone · a2f1b424
      Andi Kleen 提交于
      Add a new 4GB GFP_DMA32 zone between the GFP_DMA and GFP_NORMAL zones.
      
      As a bit of historical background: when the x86-64 port
      was originally designed we had some discussion if we should
      use a 16MB DMA zone like i386 or a 4GB DMA zone like IA64 or
      both. Both was ruled out at this point because it was in early
      2.4 when VM is still quite shakey and had bad troubles even
      dealing with one DMA zone.  We settled on the 16MB DMA zone mainly
      because we worried about older soundcards and the floppy.
      
      But this has always caused problems since then because
      device drivers had trouble getting enough DMA able memory. These days
      the VM works much better and the wide use of NUMA has proven
      it can deal with many zones successfully.
      
      So this patch adds both zones.
      
      This helps drivers who need a lot of memory below 4GB because
      their hardware is not accessing more (graphic drivers - proprietary
      and free ones, video frame buffer drivers, sound drivers etc.).
      Previously they could only use IOMMU+16MB GFP_DMA, which
      was not enough memory.
      
      Another common problem is that hardware who has full memory
      addressing for >4GB misses it for some control structures in memory
      (like transmit rings or other metadata).  They tended to allocate memory
      in the 16MB GFP_DMA or the IOMMU/swiotlb then using pci_alloc_consistent,
      but that can tie up a lot of precious 16MB GFPDMA/IOMMU/swiotlb memory
      (even on AMD systems the IOMMU tends to be quite small) especially if you have
      many devices.  With the new zone pci_alloc_consistent can just put
      this stuff into memory below 4GB which works better.
      
      One argument was still if the zone should be 4GB or 2GB. The main
      motivation for 2GB would be an unnamed not so unpopular hardware
      raid controller (mostly found in older machines from a particular four letter
      company) who has a strange 2GB restriction in firmware. But
      that one works ok with swiotlb/IOMMU anyways, so it doesn't really
      need GFP_DMA32. I chose 4GB to be compatible with IA64 and because
      it seems to be the most common restriction.
      
      The new zone is so far added only for x86-64.
      
      For other architectures who don't set up this
      new zone nothing changes. Architectures can set a compatibility
      define in Kconfig CONFIG_DMA_IS_DMA32 that will define GFP_DMA32
      as GFP_DMA. Otherwise it's a nop because on 32bit architectures
      it's normally not needed because GFP_NORMAL (=0) is DMA able
      enough.
      
      One problem is still that GFP_DMA means different things on different
      architectures. e.g. some drivers used to have #ifdef ia64  use GFP_DMA
      (trusting it to be 4GB) #elif __x86_64__ (use other hacks like
      the swiotlb because 16MB is not enough) ... . This was quite
      ugly and is now obsolete.
      
      These should be now converted to use GFP_DMA32 unconditionally. I haven't done
      this yet. Or best only use pci_alloc_consistent/dma_alloc_coherent
      which will use GFP_DMA32 transparently.
      Signed-off-by: NAndi Kleen <ak@suse.de>
      Signed-off-by: NLinus Torvalds <torvalds@osdl.org>
      a2f1b424
  14. 14 11月, 2005 1 次提交
  15. 30 10月, 2005 3 次提交
  16. 28 10月, 2005 1 次提交
  17. 05 9月, 2005 3 次提交
    • D
      [PATCH] sparsemem extreme: hotplug preparation · 28ae55c9
      Dave Hansen 提交于
      This splits up sparse_index_alloc() into two pieces.  This is needed
      because we'll allocate the memory for the second level in a different place
      from where we actually consume it to keep the allocation from happening
      underneath a lock
      Signed-off-by: NDave Hansen <haveblue@us.ibm.com>
      Signed-off-by: NBob Picco <bob.picco@hp.com>
      Cc: Andy Whitcroft <apw@shadowen.org>
      Signed-off-by: NAndrew Morton <akpm@osdl.org>
      Signed-off-by: NLinus Torvalds <torvalds@osdl.org>
      28ae55c9
    • B
      [PATCH] sparsemem extreme implementation · 3e347261
      Bob Picco 提交于
      With cleanups from Dave Hansen <haveblue@us.ibm.com>
      
      SPARSEMEM_EXTREME makes mem_section a one dimensional array of pointers to
      mem_sections.  This two level layout scheme is able to achieve smaller
      memory requirements for SPARSEMEM with the tradeoff of an additional shift
      and load when fetching the memory section.  The current SPARSEMEM
      implementation is a one dimensional array of mem_sections which is the
      default SPARSEMEM configuration.  The patch attempts isolates the
      implementation details of the physical layout of the sparsemem section
      array.
      
      SPARSEMEM_EXTREME requires bootmem to be functioning at the time of
      memory_present() calls.  This is not always feasible, so architectures
      which do not need it may allocate everything statically by using
      SPARSEMEM_STATIC.
      Signed-off-by: NAndy Whitcroft <apw@shadowen.org>
      Signed-off-by: NBob Picco <bob.picco@hp.com>
      Signed-off-by: NDave Hansen <haveblue@us.ibm.com>
      Signed-off-by: NAndrew Morton <akpm@osdl.org>
      Signed-off-by: NLinus Torvalds <torvalds@osdl.org>
      3e347261
    • B
      [PATCH] SPARSEMEM EXTREME · 802f192e
      Bob Picco 提交于
      A new option for SPARSEMEM is ARCH_SPARSEMEM_EXTREME.  Architecture
      platforms with a very sparse physical address space would likely want to
      select this option.  For those architecture platforms that don't select the
      option, the code generated is equivalent to SPARSEMEM currently in -mm.
      I'll be posting a patch on ia64 ml which uses this new SPARSEMEM feature.
      
      ARCH_SPARSEMEM_EXTREME makes mem_section a one dimensional array of
      pointers to mem_sections.  This two level layout scheme is able to achieve
      smaller memory requirements for SPARSEMEM with the tradeoff of an
      additional shift and load when fetching the memory section.  The current
      SPARSEMEM -mm implementation is a one dimensional array of mem_sections
      which is the default SPARSEMEM configuration.  The patch attempts isolates
      the implementation details of the physical layout of the sparsemem section
      array.
      
      ARCH_SPARSEMEM_EXTREME depends on 64BIT and is by default boolean false.
      
      I've boot tested under aim load ia64 configured for ARCH_SPARSEMEM_EXTREME.
       I've also boot tested a 4 way Opteron machine with !ARCH_SPARSEMEM_EXTREME
      and tested with aim.
      Signed-off-by: NAndy Whitcroft <apw@shadowen.org>
      Signed-off-by: NBob Picco <bob.picco@hp.com>
      Signed-off-by: NDave Hansen <haveblue@us.ibm.com>
      Signed-off-by: NAndrew Morton <akpm@osdl.org>
      Signed-off-by: NLinus Torvalds <torvalds@osdl.org>
      802f192e
  18. 24 6月, 2005 2 次提交
    • A
      [PATCH] sparsemem hotplug base · 29751f69
      Andy Whitcroft 提交于
      Make sparse's initalization be accessible at runtime.  This allows sparse
      mappings to be created after boot in a hotplug situation.
      
      This patch is separated from the previous one just to give an indication how
      much of the sparse infrastructure is *just* for hotplug memory.
      
      The section_mem_map doesn't really store a pointer.  It stores something that
      is convenient to do some math against to get a pointer.  It isn't valid to
      just do *section_mem_map, so I don't think it should be stored as a pointer.
      
      There are a couple of things I'd like to store about a section.  First of all,
      the fact that it is !NULL does not mean that it is present.  There could be
      such a combination where section_mem_map *is* NULL, but the math gets you
      properly to a real mem_map.  So, I don't think that check is safe.
      
      Since we're storing 32-bit-aligned structures, we have a few bits in the
      bottom of the pointer to play with.  Use one bit to encode whether there's
      really a mem_map there, and the other one to tell whether there's a valid
      section there.  We need to distinguish between the two because sometimes
      there's a gap between when a section is discovered to be present and when we
      can get the mem_map for it.
      Signed-off-by: NDave Hansen <haveblue@us.ibm.com>
      Signed-off-by: NAndy Whitcroft <apw@shadowen.org>
      Signed-off-by: NJack Steiner <steiner@sgi.com>
      Signed-off-by: NBob Picco <bob.picco@hp.com>
      Signed-off-by: NAndrew Morton <akpm@osdl.org>
      Signed-off-by: NLinus Torvalds <torvalds@osdl.org>
      29751f69
    • A
      [PATCH] sparsemem swiss cheese numa layouts · 641c7673
      Andy Whitcroft 提交于
      The part of the sparsemem patch which modifies memmap_init_zone() has recently
      become a problem.  It changes behavior so that there is a call to
      pfn_to_page() for each individual page inside of a node's range:
      node_start_pfn through node_end_pfn.  It used to simply do this once, at the
      beginning of the node, but having sparsemem's non-contiguous mem_map[]s inside
      of a node made it necessary to change.
      
      Mike Kravetz recently wrote a patch which made the NUMA code accept some new
      kinds of layouts.  The system's memory was laid out like this, with node 0's
      memory in two pieces: one before and one after node 1's memory:
      
      	Node 0: +++++     +++++
      	Node 1:      +++++
      
      Previous behavior before Mike's patch was to assign nodes like this:
      
      	Node 0: 00000     XXXXX
      	Node 1:      11111
      
      Where the 'X' areas were simply thrown away.  The new behavior was to make the
      pg_data_t span node 0 across all of its areas, including areas that are really
      node 1's: Node 0: 000000000000000 Node 1: 11111
      
      This wastes a little bit of mem_map space, but ends up being OK, and more
      fully utilizes the system's memory.  memmap_init_zone() initializes all of the
      "struct page"s for node 0, even for the "hole", but those never get used,
      because there is no pfn_to_page() that resolves to those pages.  However, only
      calling pfn_to_page() once, memmap_init_zone() always uses the pages that were
      allocated for node0->node_mem_map because:
      
      	struct page *start = pfn_to_page(start_pfn);
      	// effectively start = &node->node_mem_map[0]
      	for (page = start; page < (start + size); page++) {
      		init_page_here();...
      		page++;
      	}
      
      Slow, and wasteful, but generally harmless.
      
      But, modify that to call pfn_to_page() for each loop iteration (like sparsemem
      does):
      
      	for (pfn = start_pfn; pfn < < (start_pfn + size); pfn++++) {
      		page = pfn_to_page(pfn);
      	}
      
      And you end up trying to initialize node 1's pages too early, along with bogus
      data from node 0.  This patch checks for those weird layouts and declines to
      touch the pages, making the more frequent pfn_to_page() calls OK to do.
      Signed-off-by: NDave Hansen <haveblue@us.ibm.com>
      Signed-off-by: NAndy Whitcroft <apw@shadowen.org>
      Signed-off-by: NAndrew Morton <akpm@osdl.org>
      Signed-off-by: NLinus Torvalds <torvalds@osdl.org>
      641c7673