1. 16 Oct, 2007 40 commits
    • Greg Ungerer's avatar
      M68KNOMMU: remove unused config symbol CONFIG_DISKtel · fabc7f66
      Greg Ungerer authored
      Remove unused config symbol CONFIG_DISKtel.
      Pointed out by Robert P. J. Day <rpjday@mindspring.com>.
      Signed-off-by: default avatarGreg Ungerer <gerg@uclinux.org>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      fabc7f66
    • Thomas Gleixner's avatar
      FRV: cleanup struct irqaction initializers · a2e170ea
      Thomas Gleixner authored
      Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
      Cc: David Howells <dhowells@redhat.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      a2e170ea
    • Mariusz Kozlowski's avatar
    • Benjamin Herrenschmidt's avatar
      remove frv usage of flush_tlb_pgtables() · ef0fce85
      Benjamin Herrenschmidt authored
      frv is the last user in the tree of that dubious hook, and it's my
      understanding that it's not even needed.  It's only called by memory.c
      free_pgd_range() which is always called within an mmu_gather, and
      tlb_flush() on frv will do a flush_tlb_mm(), which from my reading of the
      code, seems to do what flush_tlb_ptables() does, which is to clear the
      cached PGE.
      Signed-off-by: default avatarBenjamin Herrenschmidt <benh@kernel.crashing.org>
      Acked-By: default avatarDavid Howells <dhowells@redhat.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      ef0fce85
    • Lee Schermerhorn's avatar
      mm: add node states sysfs class attributeS · bde631a5
      Lee Schermerhorn authored
      Add a per node state sysfs class attribute file to /sys/devices/system/node
      to display node state masks.
      
      E.g., on a 4-cell HP ia64 NUMA platform, we have 5 nodes: 4 representing
      the actual hardware cells and one memory-only pseudo-node representing a
      small amount [512MB] of "hardware interleaved" memory.  With this patch, in
      /sys/devices/system/node we see:
      
      #ls -1F /sys/devices/system/node
      has_cpu
      has_normal_memory
      node0/
      node1/
      node2/
      node3/
      node4/
      online
      possible
      #cat /sys/devices/system/node/possible
      0-255
      #cat /sys/devices/system/node/online
      0-4
      #cat /sys/devices/system/node/has_normal_memory
      0-4
      #cat /sys/devices/system/node/has_cpu
      0-3
      Signed-off-by: default avatarLee Schermerhorn <lee.schermerhorn@hp.com>
      Acked-by: default avatarChristoph Lameter <clameter@sgi.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      bde631a5
    • Adrian Bunk's avatar
      mm/vmstat.c: cleanups · e2fc88d0
      Adrian Bunk authored
      This patch contains the following cleanups:
      - make the needlessly global setup_vmstat() static
      - remove the unused refresh_vm_stats()
      Signed-off-by: default avatarAdrian Bunk <bunk@stusta.de>
      Acked-by: default avatarChristoph Lameter <clameter@sgi.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      e2fc88d0
    • Adrian Bunk's avatar
      mm/mempolicy.c: cleanups · dbcb0f19
      Adrian Bunk authored
      This patch contains the following cleanups:
      - every file should include the headers containing the prototypes for
        its global functions
      - make the follosing needlessly global functions static:
        - migrate_to_node()
        - do_mbind()
        - sp_alloc()
        - mpol_rebind_policy()
      
      [akpm@linux-foundation.org: fix uninitialised var warning]
      Signed-off-by: default avatarAdrian Bunk <bunk@stusta.de>
      Acked-by: default avatarChristoph Lameter <clameter@sgi.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      dbcb0f19
    • Adrian Bunk's avatar
      mm/shmem.c: make 3 functions static · d8dc74f2
      Adrian Bunk authored
      This patch makes three needlessly global functions static.
      Signed-off-by: default avatarAdrian Bunk <bunk@stusta.de>
      Cc: Hugh Dickins <hugh@veritas.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      d8dc74f2
    • Adam Litke's avatar
      hugetlb: fix dynamic pool resize failure case · af767cbd
      Adam Litke authored
      When gather_surplus_pages() fails to allocate enough huge pages to satisfy
      the requested reservation, it frees what it did allocate back to the buddy
      allocator.  put_page() should be called instead of update_and_free_page()
      to ensure that pool counters are updated as appropriate and the page's
      refcount is decremented.
      Signed-off-by: default avatarAdam Litke <agl@us.ibm.com>
      Acked-by: default avatarDave Hansen <haveblue@us.ibm.com>
      Cc: David Gibson <hermes@gibson.dropbear.id.au>
      Cc: William Lee Irwin III <wli@holomorphy.com>
      Cc: Badari Pulavarty <pbadari@us.ibm.com>
      Cc: Ken Chen <kenchen@google.com>
      Cc: Lee Schermerhorn <lee.schermerhorn@hp.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      af767cbd
    • Nishanth Aravamudan's avatar
      hugetlb: fix hugepage allocation with memoryless nodes · 63b4613c
      Nishanth Aravamudan authored
      Anton found a problem with the hugetlb pool allocation when some nodes have
      no memory (http://marc.info/?l=linux-mm&m=118133042025995&w=2).  Lee worked
      on versions that tried to fix it, but none were accepted.  Christoph has
      created a set of patches which allow for GFP_THISNODE allocations to fail
      if the node has no memory.
      
      Currently, alloc_fresh_huge_page() returns NULL when it is not able to
      allocate a huge page on the current node, as specified by its custom
      interleave variable.  The callers of this function, though, assume that a
      failure in alloc_fresh_huge_page() indicates no hugepages can be allocated
      on the system period.  This might not be the case, for instance, if we have
      an uneven NUMA system, and we happen to try to allocate a hugepage on a
      node with less memory and fail, while there is still plenty of free memory
      on the other nodes.
      
      To correct this, make alloc_fresh_huge_page() search through all online
      nodes before deciding no hugepages can be allocated.  Add a helper function
      for actually allocating the hugepage.  Use a new global nid iterator to
      control which nid to allocate on.
      
      Note: we expect particular semantics for __GFP_THISNODE, which are now
      enforced even for memoryless nodes.  That is, there is should be no
      fallback to other nodes.  Therefore, we rely on the nid passed into
      alloc_pages_node() to be the nid the page comes from.  If this is
      incorrect, accounting will break.
      
      Tested on x86 !NUMA, x86 NUMA, x86_64 NUMA and ppc64 NUMA (with 2
      memoryless nodes).
      
      Before on the ppc64 box:
      Trying to clear the hugetlb pool
      Done.       0 free
      Trying to resize the pool to 100
      Node 0 HugePages_Free:     25
      Node 1 HugePages_Free:     75
      Node 2 HugePages_Free:      0
      Node 3 HugePages_Free:      0
      Done. Initially     100 free
      Trying to resize the pool to 200
      Node 0 HugePages_Free:     50
      Node 1 HugePages_Free:    150
      Node 2 HugePages_Free:      0
      Node 3 HugePages_Free:      0
      Done.     200 free
      
      After:
      Trying to clear the hugetlb pool
      Done.       0 free
      Trying to resize the pool to 100
      Node 0 HugePages_Free:     50
      Node 1 HugePages_Free:     50
      Node 2 HugePages_Free:      0
      Node 3 HugePages_Free:      0
      Done. Initially     100 free
      Trying to resize the pool to 200
      Node 0 HugePages_Free:    100
      Node 1 HugePages_Free:    100
      Node 2 HugePages_Free:      0
      Node 3 HugePages_Free:      0
      Done.     200 free
      Signed-off-by: default avatarNishanth Aravamudan <nacc@us.ibm.com>
      Acked-by: default avatarChristoph Lameter <clameter@sgi.com>
      Cc: Adam Litke <agl@us.ibm.com>
      Cc: David Gibson <hermes@gibson.dropbear.id.au>
      Cc: Badari Pulavarty <pbadari@us.ibm.com>
      Cc: Ken Chen <kenchen@google.com>
      Cc: William Lee Irwin III <wli@holomorphy.com>
      Cc: Lee Schermerhorn <lee.schermerhorn@hp.com>
      Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      63b4613c
    • Adam Litke's avatar
      hugetlb: fix pool resizing corner case · 6b0c880d
      Adam Litke authored
      When shrinking the size of the hugetlb pool via the nr_hugepages sysctl, we
      are careful to keep enough pages around to satisfy reservations.  But the
      calculation is flawed for the following scenario:
      
      Action                          Pool Counters (Total, Free, Resv)
      ======                          =============
      Set pool to 1 page              1 1 0
      Map 1 page MAP_PRIVATE          1 1 0
      Touch the page to fault it in   1 0 0
      Set pool to 3 pages             3 2 0
      Map 2 pages MAP_SHARED          3 2 2
      Set pool to 2 pages             2 1 2 <-- Mistake, should be 3 2 2
      Touch the 2 shared pages        2 0 1 <-- Program crashes here
      
      The last touch above will terminate the process due to lack of huge pages.
      
      This patch corrects the calculation so that it factors in pages being used
      for private mappings.  Andrew, this is a standalone fix suitable for
      mainline.  It is also now corrected in my latest dynamic pool resizing
      patchset which I will send out soon.
      Signed-off-by: default avatarAdam Litke <agl@us.ibm.com>
      Acked-by: default avatarKen Chen <kenchen@google.com>
      Cc: David Gibson <david@gibson.dropbear.id.au>
      Cc: Badari Pulavarty <pbadari@us.ibm.com>
      Cc: William Lee Irwin III <wli@holomorphy.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      6b0c880d
    • Badari Pulavarty's avatar
      hugetlbfs read() support · e63e1e5a
      Badari Pulavarty authored
      Support for reading from hugetlbfs files.  libhugetlbfs lets application
      text/data to be placed in large pages.  When we do that, oprofile doesn't
      work - since libbfd tries to read from it.
      
      This code is very similar to what do_generic_mapping_read() does, but I
      can't use it since it has PAGE_CACHE_SIZE assumptions.
      
      [akpm@linux-foundation.org: cleanups, fix leak]
      [bunk@stusta.de: make hugetlbfs_read() static]
      Signed-off-by: default avatarBadari Pulavarty <pbadari@us.ibm.com>
      Acked-by: default avatarWilliam Irwin <bill.irwin@oracle.com>
      Tested-by: default avatarNishanth Aravamudan <nacc@us.ibm.com>
      Cc: Nick Piggin <nickpiggin@yahoo.com.au>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      e63e1e5a
    • Ken Chen's avatar
      hugetlb: allow extending ftruncate on hugetlbfs · 7aa91e10
      Ken Chen authored
      For historical reason, expanding ftruncate that increases file size on
      hugetlbfs is not allowed due to pages were pre-faulted and lack of fault
      handler.  Now that we have demand faulting on hugetlb since 2.6.15, there
      is no reason to hold back that limitation.
      
      This will make hugetlbfs behave more like a normal fs.  I'm writing a user
      level code that uses hugetlbfs but will fall back to tmpfs if there are no
      hugetlb page available in the system.  Having hugetlbfs specific ftruncate
      behavior is a bit quirky and I would like to remove that artificial
      limitation.
      
      Signed-off-by: <kenchen@google.com>
      Acked-by: default avatarWiliam Irwin <wli@holomorphy.com>
      Cc: Adam Litke <agl@us.ibm.com>
      Cc: David Gibson <david@gibson.dropbear.id.au>
      Cc: Nishanth Aravamudan <nacc@us.ibm.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      7aa91e10
    • Adam Litke's avatar
      hugetlb: Add hugetlb_dynamic_pool sysctl · 54f9f80d
      Adam Litke authored
      The maximum size of the huge page pool can be controlled using the overall
      size of the hugetlb filesystem (via its 'size' mount option).  However in the
      common case the this will not be set as the pool is traditionally fixed in
      size at boot time.  In order to maintain the expected semantics, we need to
      prevent the pool expanding by default.
      
      This patch introduces a new sysctl controlling dynamic pool resizing.  When
      this is enabled the pool will expand beyond its base size up to the size of
      the hugetlb filesystem.  It is disabled by default.
      Signed-off-by: default avatarAdam Litke <agl@us.ibm.com>
      Acked-by: default avatarAndy Whitcroft <apw@shadowen.org>
      Acked-by: default avatarDave McCracken <dave.mccracken@oracle.com>
      Cc: William Irwin <bill.irwin@oracle.com>
      Cc: David Gibson <david@gibson.dropbear.id.au>
      Cc: Ken Chen <kenchen@google.com>
      Cc: Badari Pulavarty <pbadari@us.ibm.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      54f9f80d
    • Adam Litke's avatar
      hugetlb: Try to grow hugetlb pool for MAP_SHARED mappings · e4e574b7
      Adam Litke authored
      Shared mappings require special handling because the huge pages needed to
      fully populate the VMA must be reserved at mmap time.  If not enough pages are
      available when making the reservation, allocate all of the shortfall at once
      from the buddy allocator and add the pages directly to the hugetlb pool.  If
      they cannot be allocated, then fail the mapping.  The page surplus is
      accounted for in the same way as for private mappings; faulted surplus pages
      will be freed at unmap time.  Reserved, surplus pages that have not been used
      must be freed separately when their reservation has been released.
      Signed-off-by: default avatarAdam Litke <agl@us.ibm.com>
      Acked-by: default avatarAndy Whitcroft <apw@shadowen.org>
      Acked-by: default avatarDave McCracken <dave.mccracken@oracle.com>
      Cc: William Irwin <bill.irwin@oracle.com>
      Cc: David Gibson <david@gibson.dropbear.id.au>
      Cc: Ken Chen <kenchen@google.com>
      Cc: Badari Pulavarty <pbadari@us.ibm.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      e4e574b7
    • Adam Litke's avatar
      hugetlb: Try to grow hugetlb pool for MAP_PRIVATE mappings · 7893d1d5
      Adam Litke authored
      Because we overcommit hugepages for MAP_PRIVATE mappings, it is possible that
      the hugetlb pool will be exhausted or completely reserved when a hugepage is
      needed to satisfy a page fault.  Before killing the process in this situation,
      try to allocate a hugepage directly from the buddy allocator.
      
      The explicitly configured pool size becomes a low watermark.  When dynamically
      grown, the allocated huge pages are accounted as a surplus over the watermark.
       As huge pages are freed on a node, surplus pages are released to the buddy
      allocator so that the pool will shrink back to the watermark.
      
      Surplus accounting also allows for friendlier explicit pool resizing.  When
      shrinking a pool that is fully in-use, increase the surplus so pages will be
      returned to the buddy allocator as soon as they are freed.  When growing a
      pool that has a surplus, consume the surplus first and then allocate new
      pages.
      Signed-off-by: default avatarAdam Litke <agl@us.ibm.com>
      Signed-off-by: default avatarMel Gorman <mel@csn.ul.ie>
      Acked-by: default avatarAndy Whitcroft <apw@shadowen.org>
      Acked-by: default avatarDave McCracken <dave.mccracken@oracle.com>
      Cc: William Irwin <bill.irwin@oracle.com>
      Cc: David Gibson <david@gibson.dropbear.id.au>
      Cc: Ken Chen <kenchen@google.com>
      Cc: Badari Pulavarty <pbadari@us.ibm.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      7893d1d5
    • Adam Litke's avatar
      hugetlb: Move update_and_free_page · 6af2acb6
      Adam Litke authored
      Dynamic huge page pool resizing.
      
      In most real-world scenarios, configuring the size of the hugetlb pool
      correctly is a difficult task.  If too few pages are allocated to the pool,
      applications using MAP_SHARED may fail to mmap() a hugepage region and
      applications using MAP_PRIVATE may receive SIGBUS.  Isolating too much memory
      in the hugetlb pool means it is not available for other uses, especially those
      programs not using huge pages.
      
      The obvious answer is to let the hugetlb pool grow and shrink in response to
      the runtime demand for huge pages.  The work Mel Gorman has been doing to
      establish a memory zone for movable memory allocations makes dynamically
      resizing the hugetlb pool reliable within the limits of that zone.  This patch
      series implements dynamic pool resizing for private and shared mappings while
      being careful to maintain existing semantics.  Please reply with your comments
      and feedback; even just to say whether it would be a useful feature to you.
      Thanks.
      
      How it works
      ============
      
      Upon depletion of the hugetlb pool, rather than reporting an error immediately,
      first try and allocate the needed huge pages directly from the buddy allocator.
      Care must be taken to avoid unbounded growth of the hugetlb pool, so the
      hugetlb filesystem quota is used to limit overall pool size.
      
      The real work begins when we decide there is a shortage of huge pages.  What
      happens next depends on whether the pages are for a private or shared mapping.
      Private mappings are straightforward.  At fault time, if alloc_huge_page()
      fails, we allocate a page from the buddy allocator and increment the source
      node's surplus_huge_pages counter.  When free_huge_page() is called for a page
      on a node with a surplus, the page is freed directly to the buddy allocator
      instead of the hugetlb pool.
      
      Because shared mappings require all of the pages to be reserved up front, some
      additional work must be done at mmap() to support them.  We determine the
      reservation shortage and allocate the required number of pages all at once.
      These pages are then added to the hugetlb pool and marked reserved.  Where that
      is not possible the mmap() will fail.  As with private mappings, the
      appropriate surplus counters are updated.  Since reserved huge pages won't
      necessarily be used by the process, we can't be sure that free_huge_page() will
      always be called to return surplus pages to the buddy allocator.  To prevent
      the huge page pool from bloating, we must free unused surplus pages when their
      reservation has ended.
      
      Controlling it
      ==============
      
      With the entire patch series applied, pool resizing is off by default so unless
      specific action is taken, the semantics are unchanged.
      
      To take advantage of the flexibility afforded by this patch series one must
      tolerate a change in semantics.  To control hugetlb pool growth, the following
      techniques can be employed:
      
       * A sysctl tunable to enable/disable the feature entirely
       * The size= mount option for hugetlbfs filesystems to limit pool size
      
      Performance
      ===========
      
      When contiguous memory is readily available, it is expected that the cost of
      dynamicly resizing the pool will be small.  This series has been performance
      tested with 'stream' to measure this cost.
      
      Stream (http://www.cs.virginia.edu/stream/) was linked with libhugetlbfs to
      enable remapping of the text and data/bss segments into huge pages.
      
      Stream with small array
      -----------------------
      Baseline: 	nr_hugepages = 0, No libhugetlbfs segment remapping
      Preallocated:	nr_hugepages = 5, Text and data/bss remapping
      Dynamic:	nr_hugepages = 0, Text and data/bss remapping
      
      				Rate (MB/s)
      Function	Baseline	Preallocated	Dynamic
      Copy:		4695.6266	5942.8371	5982.2287
      Scale:		4451.5776	5017.1419	5658.7843
      Add:		5815.8849	7927.7827	8119.3552
      Triad:		5949.4144	8527.6492	8110.6903
      
      Stream with large array
      -----------------------
      Baseline: 	nr_hugepages =  0, No libhugetlbfs segment remapping
      Preallocated:	nr_hugepages = 67, Text and data/bss remapping
      Dynamic:	nr_hugepages =  0, Text and data/bss remapping
      
      				Rate (MB/s)
      Function	Baseline	Preallocated	Dynamic
      Copy:		2227.8281	2544.2732	2546.4947
      Scale:		2136.3208	2430.7294	2421.2074
      Add:		2773.1449	4004.0021	3999.4331
      Triad:		2748.4502	3777.0109	3773.4970
      
      * All numbers are averages taken from 10 consecutive runs with a maximum
        standard deviation of 1.3 percent noted.
      
      This patch:
      
      Simply move update_and_free_page() so that it can be reused later in this
      patch series.  The implementation is not changed.
      Signed-off-by: default avatarAdam Litke <agl@us.ibm.com>
      Acked-by: default avatarAndy Whitcroft <apw@shadowen.org>
      Acked-by: default avatarDave McCracken <dave.mccracken@oracle.com>
      Acked-by: default avatarWilliam Irwin <bill.irwin@oracle.com>
      Cc: David Gibson <david@gibson.dropbear.id.au>
      Cc: Ken Chen <kenchen@google.com>
      Cc: Badari Pulavarty <pbadari@us.ibm.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      6af2acb6
    • Yasunori Goto's avatar
      memory hotplug: Hot-add with sparsemem-vmemmap · 98f3cfc1
      Yasunori Goto authored
      This patch is to avoid panic when memory hot-add is executed with
      sparsemem-vmemmap.  Current vmemmap-sparsemem code doesn't support memory
      hot-add.  Vmemmap must be populated when hot-add.  This is for
      2.6.23-rc2-mm2.
      
      Todo: # Even if this patch is applied, the message "[xxxx-xxxx] potential
              offnode page_structs" is displayed. To allocate memmap on its node,
              memmap (and pgdat) must be initialized itself like chicken and
              egg relationship.
      
            # vmemmap_unpopulate will be necessary for followings.
               - For cancel hot-add due to error.
               - For unplug.
      Signed-off-by: default avatarYasunori Goto <y-goto@jp.fujitsu.com>
      Cc: Andy Whitcroft <apw@shadowen.org>
      Cc: Christoph Lameter <clameter@sgi.com>
      Cc: Mel Gorman <mel@csn.ul.ie>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      98f3cfc1
    • KAMEZAWA Hiroyuki's avatar
      fix memory hot remove not configured case. · 48e94196
      KAMEZAWA Hiroyuki authored
      Now, arch dependent code around CONFIG_MEMORY_HOTREMOVE is a mess.
      This patch cleans up them. This is against 2.6.23-rc6-mm1.
      
       - fix compile failure on ia64/ CONFIG_MEMORY_HOTPLUG && !CONFIG_MEMORY_HOTREMOVE case.
       - For !CONFIG_MEMORY_HOTREMOVE, add generic no-op remove_memory(),
         which returns -EINVAL.
       - removed remove_pages() only used in powerpc.
       - removed no-op remove_memory() in i386, sh, sparc64, x86_64.
      
       - only powerpc returns -ENOSYS at memory hot remove(no-op). changes it
         to return -EINVAL.
      
      Note:
      Currently, only ia64 supports CONFIG_MEMORY_HOTREMOVE. I welcome other
      archs if there are requirements and testers.
      Signed-off-by: default avatarKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      48e94196
    • KAMEZAWA Hiroyuki's avatar
      memory unplug: ia64 interface · de33b821
      KAMEZAWA Hiroyuki authored
      IA64 memory unplug interface.
      Signed-off-by: default avatarKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      de33b821
    • KAMEZAWA Hiroyuki's avatar
      memory unplug: page offline · 0c0e6195
      KAMEZAWA Hiroyuki authored
      Logic.
       - set all pages in  [start,end)  as isolated migration-type.
         by this, all free pages in the range will be not-for-use.
       - Migrate all LRU pages in the range.
       - Test all pages in the range's refcnt is zero or not.
      
      Todo:
       - allocate migration destination page from better area.
       - confirm page_count(page)== 0 && PageReserved(page) page is safe to be freed..
       (I don't like this kind of page but..
       - Find out pages which cannot be migrated.
       - more running tests.
       - Use reclaim for unplugging other memory type area.
      Signed-off-by: default avatarKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
      Signed-off-by: default avatarYasunori Goto <y-goto@jp.fujitsu.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      0c0e6195
    • KAMEZAWA Hiroyuki's avatar
      memory unplug: page isolation · a5d76b54
      KAMEZAWA Hiroyuki authored
      Implement generic chunk-of-pages isolation method by using page grouping ops.
      
      This patch add MIGRATE_ISOLATE to MIGRATE_TYPES. By this
       - MIGRATE_TYPES increases.
       - bitmap for migratetype is enlarged.
      
      pages of MIGRATE_ISOLATE migratetype will not be allocated even if it is free.
      By this, you can isolated *freed* pages from users. How-to-free pages is not
      a purpose of this patch. You may use reclaim and migrate codes to free pages.
      
      If start_isolate_page_range(start,end) is called,
       - migratetype of the range turns to be MIGRATE_ISOLATE  if
         its type is MIGRATE_MOVABLE. (*) this check can be updated if other
         memory reclaiming works make progress.
       - MIGRATE_ISOLATE is not on migratetype fallback list.
       - All free pages and will-be-freed pages are isolated.
      To check all pages in the range are isolated or not,  use test_pages_isolated(),
      To cancel isolation, use undo_isolate_page_range().
      
      Changes V6 -> V7
       - removed unnecessary #ifdef
      
      There are HOLES_IN_ZONE handling codes...I'm glad if we can remove them..
      Signed-off-by: default avatarYasunori Goto <y-goto@jp.fujitsu.com>
      Signed-off-by: default avatarKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      a5d76b54
    • KAMEZAWA Hiroyuki's avatar
      memory unplug: memory hotplug cleanup · 75884fb1
      KAMEZAWA Hiroyuki authored
      A clean up patch for "scanning memory resource [start, end)" operation.
      
      Now, find_next_system_ram() function is used in memory hotplug, but this
      interface is not easy to use and codes are complicated.
      
      This patch adds walk_memory_resouce(start,len,arg,func) function.
      The function 'func' is called per valid memory resouce range in [start,pfn).
      
      [pbadari@us.ibm.com: Error handling in walk_memory_resource()]
      Signed-off-by: default avatarKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
      Signed-off-by: default avatarBadari Pulavarty <pbadari@us.ibm.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      75884fb1
    • Mel Gorman's avatar
      Breakout page_order() to internal.h to avoid special knowledge of the buddy allocator · 48f13bf3
      Mel Gorman authored
      The statistics patch later needs to know what order a free page is on the free
      lists.  Rather than having special knowledge of page_private() when
      PageBuddy() is set, this patch places out page_order() in internal.h and adds
      a VM_BUG_ON to catch using it on non-PageBuddy pages.
      Signed-off-by: default avatarMel Gorman <mel@csn.ul.ie>
      Signed-off-by: default avatarChristoph Lameter <clameter@sgi.com>
      Acked-by: default avatarAndy Whitcroft <apw@shadowen.org>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      48f13bf3
    • Andrew Morton's avatar
      slub: list_locations() can use GFP_TEMPORARY · ea3061d2
      Andrew Morton authored
      It's a short-lived allocation.
      
      Cc: Christoph Lameter <clameter@sgi.com>
      Cc: Mel Gorman <mel@csn.ul.ie>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      ea3061d2
    • Christoph Lameter's avatar
      SLUB: Optimize cacheline use for zeroing · 42a9fdbb
      Christoph Lameter authored
      We touch a cacheline in the kmem_cache structure for zeroing to get the
      size. However, the hot paths in slab_alloc and slab_free do not reference
      any other fields in kmem_cache, so we may have to just bring in the
      cacheline for this one access.
      
      Add a new field to kmem_cache_cpu that contains the object size. That
      cacheline must already be used in the hotpaths. So we save one cacheline
      on every slab_alloc if we zero.
      
      We need to update the kmem_cache_cpu object size if an aliasing operation
      changes the objsize of an non debug slab.
      Signed-off-by: default avatarChristoph Lameter <clameter@sgi.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      42a9fdbb
    • Christoph Lameter's avatar
      SLUB: Place kmem_cache_cpu structures in a NUMA aware way · 4c93c355
      Christoph Lameter authored
      The kmem_cache_cpu structures introduced are currently an array placed in the
      kmem_cache struct. Meaning the kmem_cache_cpu structures are overwhelmingly
      on the wrong node for systems with a higher amount of nodes. These are
      performance critical structures since the per node information has
      to be touched for every alloc and free in a slab.
      
      In order to place the kmem_cache_cpu structure optimally we put an array
      of pointers to kmem_cache_cpu structs in kmem_cache (similar to SLAB).
      
      However, the kmem_cache_cpu structures can now be allocated in a more
      intelligent way.
      
      We would like to put per cpu structures for the same cpu but different
      slab caches in cachelines together to save space and decrease the cache
      footprint. However, the slab allocators itself control only allocations
      per node. We set up a simple per cpu array for every processor with
      100 per cpu structures which is usually enough to get them all set up right.
      If we run out then we fall back to kmalloc_node. This also solves the
      bootstrap problem since we do not have to use slab allocator functions
      early in boot to get memory for the small per cpu structures.
      
      Pro:
      	- NUMA aware placement improves memory performance
      	- All global structures in struct kmem_cache become readonly
      	- Dense packing of per cpu structures reduces cacheline
      	  footprint in SMP and NUMA.
      	- Potential avoidance of exclusive cacheline fetches
      	  on the free and alloc hotpath since multiple kmem_cache_cpu
      	  structures are in one cacheline. This is particularly important
      	  for the kmalloc array.
      
      Cons:
      	- Additional reference to one read only cacheline (per cpu
      	  array of pointers to kmem_cache_cpu) in both slab_alloc()
      	  and slab_free().
      
      [akinobu.mita@gmail.com: fix cpu hotplug offline/online path]
      Signed-off-by: default avatarChristoph Lameter <clameter@sgi.com>
      Cc: "Pekka Enberg" <penberg@cs.helsinki.fi>
      Cc: Akinobu Mita <akinobu.mita@gmail.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      4c93c355
    • Christoph Lameter's avatar
      SLUB: Avoid touching page struct when freeing to per cpu slab · ee3c72a1
      Christoph Lameter authored
      Set c->node to -1 if we allocate from a debug slab instead for SlabDebug
      which requires access the page struct cacheline.
      Signed-off-by: default avatarChristoph Lameter <clameter@sgi.com>
      Tested-by: default avatarAlexey Dobriyan <adobriyan@sw.ru>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      ee3c72a1
    • Christoph Lameter's avatar
      SLUB: Move page->offset to kmem_cache_cpu->offset · b3fba8da
      Christoph Lameter authored
      We need the offset from the page struct during slab_alloc and slab_free. In
      both cases we also reference the cacheline of the kmem_cache_cpu structure.
      We can therefore move the offset field into the kmem_cache_cpu structure
      freeing up 16 bits in the page struct.
      
      Moving the offset allows an allocation from slab_alloc() without touching the
      page struct in the hot path.
      
      The only thing left in slab_free() that touches the page struct cacheline for
      per cpu freeing is the checking of SlabDebug(page). The next patch deals with
      that.
      
      Use the available 16 bits to broaden page->inuse. More than 64k objects per
      slab become possible and we can get rid of the checks for that limitation.
      
      No need anymore to shrink the order of slabs if we boot with 2M sized slabs
      (slub_min_order=9).
      
      No need anymore to switch off the offset calculation for very large slabs
      since the field in the kmem_cache_cpu structure is 32 bits and so the offset
      field can now handle slab sizes of up to 8GB.
      Signed-off-by: default avatarChristoph Lameter <clameter@sgi.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      b3fba8da
    • Christoph Lameter's avatar
      SLUB: Do not use page->mapping · 8e65d24c
      Christoph Lameter authored
      After moving the lockless_freelist to kmem_cache_cpu we no longer need
      page->lockless_freelist. Restructure the use of the struct page fields in
      such a way that we never touch the mapping field.
      
      This is turn allows us to remove the special casing of SLUB when determining
      the mapping of a page (needed for corner cases of virtual caches machines that
      need to flush caches of processors mapping a page).
      Signed-off-by: default avatarChristoph Lameter <clameter@sgi.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      8e65d24c
    • Christoph Lameter's avatar
      SLUB: Avoid page struct cacheline bouncing due to remote frees to cpu slab · dfb4f096
      Christoph Lameter authored
      A remote free may access the same page struct that also contains the lockless
      freelist for the cpu slab. If objects have a short lifetime and are freed by
      a different processor then remote frees back to the slab from which we are
      currently allocating are frequent. The cacheline with the page struct needs
      to be repeately acquired in exclusive mode by both the allocating thread and
      the freeing thread. If this is frequent enough then performance will suffer
      because of cacheline bouncing.
      
      This patchset puts the lockless_freelist pointer in its own cacheline. In
      order to make that happen we introduce a per cpu structure called
      kmem_cache_cpu.
      
      Instead of keeping an array of pointers to page structs we now keep an array
      to a per cpu structure that--among other things--contains the pointer to the
      lockless freelist. The freeing thread can then keep possession of exclusive
      access to the page struct cacheline while the allocating thread keeps its
      exclusive access to the cacheline containing the per cpu structure.
      
      This works as long as the allocating cpu is able to service its request
      from the lockless freelist. If the lockless freelist runs empty then the
      allocating thread needs to acquire exclusive access to the cacheline with
      the page struct lock the slab.
      
      The allocating thread will then check if new objects were freed to the per
      cpu slab. If so it will keep the slab as the cpu slab and continue with the
      recently remote freed objects. So the allocating thread can take a series
      of just freed remote pages and dish them out again. Ideally allocations
      could be just recycling objects in the same slab this way which will lead
      to an ideal allocation / remote free pattern.
      
      The number of objects that can be handled in this way is limited by the
      capacity of one slab. Increasing slab size via slub_min_objects/
      slub_max_order may increase the number of objects and therefore performance.
      
      If the allocating thread runs out of objects and finds that no objects were
      put back by the remote processor then it will retrieve a new slab (from the
      partial lists or from the page allocator) and start with a whole
      new set of objects while the remote thread may still be freeing objects to
      the old cpu slab. This may then repeat until the new slab is also exhausted.
      If remote freeing has freed objects in the earlier slab then that earlier
      slab will now be on the partial freelist and the allocating thread will
      pick that slab next for allocation. So the loop is extended. However,
      both threads need to take the list_lock to make the swizzling via
      the partial list happen.
      
      It is likely that this kind of scheme will keep the objects being passed
      around to a small set that can be kept in the cpu caches leading to increased
      performance.
      
      More code cleanups become possible:
      
      - Instead of passing a cpu we can now pass a kmem_cache_cpu structure around.
        Allows reducing the number of parameters to various functions.
      - Can define a new node_match() function for NUMA to encapsulate locality
        checks.
      
      Effect on allocations:
      
      Cachelines touched before this patch:
      
      	Write:	page cache struct and first cacheline of object
      
      Cachelines touched after this patch:
      
      	Write:	kmem_cache_cpu cacheline and first cacheline of object
      	Read: page cache struct (but see later patch that avoids touching
      		that cacheline)
      
      The handling when the lockless alloc list runs empty gets to be a bit more
      complicated since another cacheline has now to be written to. But that is
      halfway out of the hot path.
      
      Effect on freeing:
      
      Cachelines touched before this patch:
      
      	Write: page_struct and first cacheline of object
      
      Cachelines touched after this patch depending on how we free:
      
        Write(to cpu_slab):	kmem_cache_cpu struct and first cacheline of object
        Write(to other):	page struct and first cacheline of object
      
        Read(to cpu_slab):	page struct to id slab etc. (but see later patch that
        			avoids touching the page struct on free)
        Read(to other):	cpu local kmem_cache_cpu struct to verify its not
        			the cpu slab.
      
      Summary:
      
      Pro:
      	- Distinct cachelines so that concurrent remote frees and local
      	  allocs on a cpuslab can occur without cacheline bouncing.
      	- Avoids potential bouncing cachelines because of neighboring
      	  per cpu pointer updates in kmem_cache's cpu_slab structure since
      	  it now grows to a cacheline (Therefore remove the comment
      	  that talks about that concern).
      
      Cons:
      	- Freeing objects now requires the reading of one additional
      	  cacheline. That can be mitigated for some cases by the following
      	  patches but its not possible to completely eliminate these
      	  references.
      
      	- Memory usage grows slightly.
      
      	The size of each per cpu object is blown up from one word
      	(pointing to the page_struct) to one cacheline with various data.
      	So this is NR_CPUS*NR_SLABS*L1_BYTES more memory use. Lets say
      	NR_SLABS is 100 and a cache line size of 128 then we have just
      	increased SLAB metadata requirements by 12.8k per cpu.
      	(Another later patch reduces these requirements)
      Signed-off-by: default avatarChristoph Lameter <clameter@sgi.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      dfb4f096
    • Adrian Bunk's avatar
      mm/page_alloc.c: make code static · 484f51f8
      Adrian Bunk authored
      This patch makes needlessly global code static.
      Signed-off-by: default avatarAdrian Bunk <bunk@stusta.de>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      484f51f8
    • Mel Gorman's avatar
      Print out statistics in relation to fragmentation avoidance to /proc/pagetypeinfo · 467c996c
      Mel Gorman authored
      This patch provides fragmentation avoidance statistics via /proc/pagetypeinfo.
       The information is collected only on request so there is no runtime overhead.
       The statistics are in three parts:
      
      The first part prints information on the size of blocks that pages are
      being grouped on and looks like
      
      Page block order: 10
      Pages per block:  1024
      
      The second part is a more detailed version of /proc/buddyinfo and looks like
      
      Free pages count per migrate type at order       0      1      2      3      4      5      6      7      8      9     10
      Node    0, zone      DMA, type    Unmovable      0      0      0      0      0      0      0      0      0      0      0
      Node    0, zone      DMA, type  Reclaimable      1      0      0      0      0      0      0      0      0      0      0
      Node    0, zone      DMA, type      Movable      0      0      0      0      0      0      0      0      0      0      0
      Node    0, zone      DMA, type      Reserve      0      4      4      0      0      0      0      1      0      1      0
      Node    0, zone   Normal, type    Unmovable    111      8      4      4      2      3      1      0      0      0      0
      Node    0, zone   Normal, type  Reclaimable    293     89      8      0      0      0      0      0      0      0      0
      Node    0, zone   Normal, type      Movable      1      6     13      9      7      6      3      0      0      0      0
      Node    0, zone   Normal, type      Reserve      0      0      0      0      0      0      0      0      0      0      4
      
      The third part looks like
      
      Number of blocks type     Unmovable  Reclaimable      Movable      Reserve
      Node 0, zone      DMA            0            1            2            1
      Node 0, zone   Normal            3           17           94            4
      
      To walk the zones within a node with interrupts disabled, walk_zones_in_node()
      is introduced and shared between /proc/buddyinfo, /proc/zoneinfo and
      /proc/pagetypeinfo to reduce code duplication.  It seems specific to what
      vmstat.c requires but could be broken out as a general utility function in
      mmzone.c if there were other other potential users.
      Signed-off-by: default avatarMel Gorman <mel@csn.ul.ie>
      Acked-by: default avatarAndy Whitcroft <apw@shadowen.org>
      Acked-by: default avatarChristoph Lameter <clameter@sgi.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      467c996c
    • Mel Gorman's avatar
      Do not depend on MAX_ORDER when grouping pages by mobility · d9c23400
      Mel Gorman authored
      Currently mobility grouping works at the MAX_ORDER_NR_PAGES level.  This makes
      sense for the majority of users where this is also the huge page size.
      However, on platforms like ia64 where the huge page size is runtime
      configurable it is desirable to group at a lower order.  On x86_64 and
      occasionally on x86, the hugepage size may not always be MAX_ORDER_NR_PAGES.
      
      This patch groups pages together based on the value of HUGETLB_PAGE_ORDER.  It
      uses a compile-time constant if possible and a variable where the huge page
      size is runtime configurable.
      
      It is assumed that grouping should be done at the lowest sensible order and
      that the user would not want to override this.  If this is not true,
      page_block order could be forced to a variable initialised via a boot-time
      kernel parameter.
      
      One potential issue with this patch is that IA64 now parses hugepagesz with
      early_param() instead of __setup().  __setup() is called after the memory
      allocator has been initialised and the pageblock bitmaps already setup.  In
      tests on one IA64 there did not seem to be any problem with using
      early_param() and in fact may be more correct as it guarantees the parameter
      is handled before the parsing of hugepages=.
      Signed-off-by: default avatarMel Gorman <mel@csn.ul.ie>
      Acked-by: default avatarAndy Whitcroft <apw@shadowen.org>
      Acked-by: default avatarChristoph Lameter <clameter@sgi.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      d9c23400
    • Mel Gorman's avatar
      Fix calculation in move_freepages_block for counting pages · d100313f
      Mel Gorman authored
      move_freepages_block() returns the number of blocks moved.  This value is used
      to determine if a block of pages should be stolen for the exclusive use of a
      migrate type or not.  However, the value returned is being used correctly.
      This patch fixes the calculation to return the number of base pages that have
      been moved.
      
      This should be considered a fix to the patch
      move-free-pages-between-lists-on-steal.patch
      
      Credit to Andy Whitcroft for spotting the problem.
      Signed-off-by: default avatarMel Gorman <mel@csn.ul.ie>
      Acked-by: default avatarAndy Whitcroft <apw@shadowen.org>
      Acked-by: default avatarChristoph Lameter <clameter@sgi.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      d100313f
    • Mel Gorman's avatar
      don't group high order atomic allocations · 64c5e135
      Mel Gorman authored
      Grouping high-order atomic allocations together was intended to allow
      bursty users of atomic allocations to work such as e1000 in situations
      where their preallocated buffers were depleted.  This did not work in at
      least one case with a wireless network adapter needing order-1 allocations
      frequently.  To resolve that, the free pages used for min_free_kbytes were
      moved to separate contiguous blocks with the patch
      bias-the-location-of-pages-freed-for-min_free_kbytes-in-the-same-max_order_nr_pages-blocks.
      
      It is felt that keeping the free pages in the same contiguous blocks should
      be sufficient for bursty short-lived high-order atomic allocations to
      succeed, maybe even with the e1000.  Even if there is a failure, increasing
      the value of min_free_kbytes will free pages as contiguous bloks in
      contrast to the standard buddy allocator which makes no attempt to keep the
      minimum number of free pages contiguous.
      
      This patch backs out grouping high order atomic allocations together to
      determine if it is really needed or not.  If a new report comes in about
      high-order atomic allocations failing, the feature can be reintroduced to
      determine if it fixes the problem or not.  As a side-effect, this patch
      reduces by 1 the number of bits required to track the mobility type of
      pages within a MAX_ORDER_NR_PAGES block.
      Signed-off-by: default avatarMel Gorman <mel@csn.ul.ie>
      Acked-by: default avatarAndy Whitcroft <apw@shadowen.org>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      64c5e135
    • Mel Gorman's avatar
      remove PAGE_GROUP_BY_MOBILITY · ac0e5b7a
      Mel Gorman authored
      Grouping pages by mobility can be disabled at compile-time. This was
      considered undesirable by a number of people. However, in the current stack of
      patches, it is not a simple case of just dropping the configurable patch as it
      would cause merge conflicts.  This patch backs out the configuration option.
      Signed-off-by: default avatarMel Gorman <mel@csn.ul.ie>
      Acked-by: default avatarAndy Whitcroft <apw@shadowen.org>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      ac0e5b7a
    • Mel Gorman's avatar
      Bias the location of pages freed for min_free_kbytes in the same MAX_ORDER_NR_PAGES blocks · 56fd56b8
      Mel Gorman authored
      The standard buddy allocator always favours the smallest block of pages.
      The effect of this is that the pages free to satisfy min_free_kbytes tends
      to be preserved since boot time at the same location of memory ffor a very
      long time and as a contiguous block.  When an administrator sets the
      reserve at 16384 at boot time, it tends to be the same MAX_ORDER blocks
      that remain free.  This allows the occasional high atomic allocation to
      succeed up until the point the blocks are split.  In practice, it is
      difficult to split these blocks but when they do split, the benefit of
      having min_free_kbytes for contiguous blocks disappears.  Additionally,
      increasing min_free_kbytes once the system has been running for some time
      has no guarantee of creating contiguous blocks.
      
      On the other hand, CONFIG_PAGE_GROUP_BY_MOBILITY favours splitting large
      blocks when there are no free pages of the appropriate type available.  A
      side-effect of this is that all blocks in memory tends to be used up and
      the contiguous free blocks from boot time are not preserved like in the
      vanilla allocator.  This can cause a problem if a new caller is unwilling
      to reclaim or does not reclaim for long enough.
      
      A failure scenario was found for a wireless network device allocating
      order-1 atomic allocations but the allocations were not intense or frequent
      enough for a whole block of pages to be preserved for MIGRATE_HIGHALLOC.
      This was reproduced on a desktop by booting with mem=256mb, forcing the
      driver to allocate at order-1, running a bittorrent client (downloading a
      debian ISO) and building a kernel with -j2.
      
      This patch addresses the problem on the desktop machine booted with
      mem=256mb.  It works by setting aside a reserve of MAX_ORDER_NR_PAGES
      blocks, the number of which depends on the value of min_free_kbytes.  These
      blocks are only fallen back to when there is no other free pages.  Then the
      smallest possible page is used just like the normal buddy allocator instead
      of the largest possible page to preserve contiguous pages The pages in free
      lists in the reserve blocks are never taken for another migrate type.  The
      results is that even if min_free_kbytes is set to a low value, contiguous
      blocks will be preserved in the MIGRATE_RESERVE blocks.
      
      This works better than the vanilla allocator because if min_free_kbytes is
      increased, a new reserve block will be chosen based on the location of
      reclaimable pages and the block will free up as contiguous pages.  In the
      vanilla allocator, no effort is made to target a block of pages to free as
      contiguous pages and min_free_kbytes pages are scattered randomly.
      
      This effect has been observed on the test machine.  min_free_kbytes was set
      initially low but it was kept as a contiguous free block within
      MIGRATE_RESERVE.  min_free_kbytes was then set to a higher value and over a
      period of time, the free blocks were within the reserve and coalescing.
      How long it takes to free up depends on how quickly LRU is rotating.
      Amusingly, this means that more activity will free the blocks faster.
      
      This mechanism potentially replaces MIGRATE_HIGHALLOC as it may be more
      effective than grouping contiguous free pages together.  It all depends on
      whether the number of active atomic high allocations exceeds
      min_free_kbytes or not.  If the number of active allocations exceeds
      min_free_kbytes, it's worth it but maybe in that situation, min_free_kbytes
      should be set higher.  Once there are no more reports of allocation
      failures, a patch will be submitted that backs out MIGRATE_HIGHALLOC and
      see if the reports stay missing.
      
      Credit to Mariusz Kozlowski for discovering the problem, describing the
      failure scenario and testing patches and scenarios.
      
      [akpm@linux-foundation.org: cleanups]
      Signed-off-by: default avatarMel Gorman <mel@csn.ul.ie>
      Acked-by: default avatarAndy Whitcroft <apw@shadowen.org>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      56fd56b8
    • Mel Gorman's avatar
      Fix corruption of memmap on IA64 SPARSEMEM when mem_section is not a power of 2 · 5c0e3066
      Mel Gorman authored
      There are problems in the use of SPARSEMEM and pageblock flags that causes
      problems on ia64.
      
      The first part of the problem is that units are incorrect in
      SECTION_BLOCKFLAGS_BITS computation.  This results in a map_section's
      section_mem_map being treated as part of a bitmap which isn't good.  This
      was evident with an invalid virtual address when mem_init attempted to free
      bootmem pages while relinquishing control from the bootmem allocator.
      
      The second part of the problem occurs because the pageblock flags bitmap is
      be located with the mem_section.  The SECTIONS_PER_ROOT computation using
      sizeof (mem_section) may not be a power of 2 depending on the size of the
      bitmap.  This renders masks and other such things not power of 2 base.
      This issue was seen with SPARSEMEM_EXTREME on ia64.  This patch moves the
      bitmap outside of mem_section and uses a pointer instead in the
      mem_section.  The bitmaps are allocated when the section is being
      initialised.
      
      Note that sparse_early_usemap_alloc() does not use alloc_remap() like
      sparse_early_mem_map_alloc().  The allocation required for the bitmap on
      x86, the only architecture that uses alloc_remap is typically smaller than
      a cache line.  alloc_remap() pads out allocations to the cache size which
      would be a needless waste.
      
      Credit to Bob Picco for identifying the original problem and effecting a
      fix for the SECTION_BLOCKFLAGS_BITS calculation.  Credit to Andy Whitcroft
      for devising the best way of allocating the bitmaps only when required for
      the section.
      
      [wli@holomorphy.com: warning fix]
      Signed-off-by: default avatarBob Picco <bob.picco@hp.com>
      Signed-off-by: default avatarAndy Whitcroft <apw@shadowen.org>
      Signed-off-by: default avatarMel Gorman <mel@csn.ul.ie>
      Cc: "Luck, Tony" <tony.luck@intel.com>
      Signed-off-by: default avatarWilliam Irwin <bill.irwin@oracle.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      5c0e3066
    • Mel Gorman's avatar
      Be more agressive about stealing when MIGRATE_RECLAIMABLE allocations fallback · 46dafbca
      Mel Gorman authored
      MIGRATE_RECLAIMABLE allocations tend to be very bursty in nature like when
      updatedb starts.  It is likely this will occur in situations where MAX_ORDER
      blocks of pages are not free.  This means that updatedb can scatter
      MIGRATE_RECLAIMABLE pages throughout the address space.  This patch is more
      agressive about stealing blocks of pages for MIGRATE_RECLAIMABLE.
      Signed-off-by: default avatarMel Gorman <mel@csn.ul.ie>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      46dafbca