1. 22 Jan, 2014 2 commits
    • Andrea Arcangeli's avatar
      mm: tail page refcounting optimization for slab and hugetlbfs · 44518d2b
      Andrea Arcangeli authored
      
      
      This skips the _mapcount mangling for slab and hugetlbfs pages.
      
      The main trouble in doing this is to guarantee that PageSlab and
      PageHeadHuge remains constant for all get_page/put_page run on the tail
      of slab or hugetlbfs compound pages.  Otherwise if they're set during
      get_page but not set during put_page, the _mapcount of the tail page
      would underflow.
      
      PageHeadHuge will remain true until the compound page is released and
      enters the buddy allocator so it won't risk to change even if the tail
      page is the last reference left on the page.
      
      PG_slab instead is cleared before the slab frees the head page with
      put_page, so if the tail pin is released after the slab freed the page,
      we would have a problem.  But in the slab case the tail pin cannot be
      the last reference left on the page.  This is because the slab code is
      free to reuse the compound page after a kfree/kmem_cache_free without
      having to check if there's any tail pin left.  In turn all tail pins
      must be always released while the head is still pinned by the slab code
      and so we know PG_slab will be still set too.
      
      Signed-off-by: default avatarAndrea Arcangeli <aarcange@redhat.com>
      Reviewed-by: default avatarKhalid Aziz <khalid.aziz@oracle.com>
      Cc: Pravin Shelar <pshelar@nicira.com>
      Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
      Cc: Ben Hutchings <bhutchings@solarflare.com>
      Cc: Christoph Lameter <cl@linux.com>
      Cc: Johannes Weiner <jweiner@redhat.com>
      Cc: Mel Gorman <mgorman@suse.de>
      Cc: Rik van Riel <riel@redhat.com>
      Cc: Andi Kleen <andi@firstfloor.org>
      Cc: Minchan Kim <minchan@kernel.org>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      44518d2b
    • Geert Uytterhoeven's avatar
      mm: Make {,set}page_address() static inline if WANT_PAGE_VIRTUAL · f92f455f
      Geert Uytterhoeven authored
      
      
      {,set}page_address() are macros if WANT_PAGE_VIRTUAL.  If
      !WANT_PAGE_VIRTUAL, they're plain C functions.
      
      If someone calls them with a void *, this pointer is auto-converted to
      struct page * if !WANT_PAGE_VIRTUAL, but causes a build failure on
      architectures using WANT_PAGE_VIRTUAL (arc, m68k and sparc64):
      
        drivers/md/bcache/bset.c: In function `__btree_sort':
        drivers/md/bcache/bset.c:1190: warning: dereferencing `void *' pointer
        drivers/md/bcache/bset.c:1190: error: request for member `virtual' in something not a structure or union
      
      Convert them to static inline functions to fix this.  There are already
      plenty of users of struct page members inside <linux/mm.h>, so there's
      no reason to keep them as macros.
      
      Signed-off-by: default avatarGeert Uytterhoeven <geert@linux-m68k.org>
      Acked-by: default avatarMichael S. Tsirkin <mst@redhat.com>
      Tested-by: default avatarGuenter Roeck <linux@roeck-us.net>
      Tested-by: default avatarDavid Rientjes <rientjes@google.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      f92f455f
  2. 20 Dec, 2013 1 commit
  3. 20 Nov, 2013 1 commit
  4. 15 Nov, 2013 8 commits
  5. 13 Nov, 2013 1 commit
    • Tang Chen's avatar
      mm/memblock.c: introduce bottom-up allocation mode · 79442ed1
      Tang Chen authored
      
      
      The Linux kernel cannot migrate pages used by the kernel.  As a result,
      kernel pages cannot be hot-removed.  So we cannot allocate hotpluggable
      memory for the kernel.
      
      ACPI SRAT (System Resource Affinity Table) contains the memory hotplug
      info.  But before SRAT is parsed, memblock has already started to allocate
      memory for the kernel.  So we need to prevent memblock from doing this.
      
      In a memory hotplug system, any numa node the kernel resides in should be
      unhotpluggable.  And for a modern server, each node could have at least
      16GB memory.  So memory around the kernel image is highly likely
      unhotpluggable.
      
      So the basic idea is: Allocate memory from the end of the kernel image and
      to the higher memory.  Since memory allocation before SRAT is parsed won't
      be too much, it could highly likely be in the same node with kernel image.
      
      The current memblock can only allocate memory top-down.  So this patch
      introduces a new bottom-up allocation mode to allocate memory bottom-up.
      And later when we use this allocation direction to allocate memory, we
      will limit the start address above the kernel.
      
      Signed-off-by: default avatarTang Chen <tangchen@cn.fujitsu.com>
      Signed-off-by: default avatarZhang Yanfei <zhangyanfei@cn.fujitsu.com>
      Acked-by: default avatarToshi Kani <toshi.kani@hp.com>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Cc: Ingo Molnar <mingo@elte.hu>
      Cc: "H. Peter Anvin" <hpa@zytor.com>
      Cc: Tejun Heo <tj@kernel.org>
      Cc: Wanpeng Li <liwanp@linux.vnet.ibm.com>
      Cc: Thomas Renninger <trenn@suse.de>
      Cc: Yinghai Lu <yinghai@kernel.org>
      Cc: Jiang Liu <jiang.liu@huawei.com>
      Cc: Wen Congyang <wency@cn.fujitsu.com>
      Cc: Lai Jiangshan <laijs@cn.fujitsu.com>
      Cc: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
      Cc: Taku Izumi <izumi.taku@jp.fujitsu.com>
      Cc: Mel Gorman <mgorman@suse.de>
      Cc: Michal Nazarewicz <mina86@mina86.com>
      Cc: Minchan Kim <minchan@kernel.org>
      Cc: Rik van Riel <riel@redhat.com>
      Cc: Johannes Weiner <hannes@cmpxchg.org>
      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>
      79442ed1
  6. 11 Oct, 2013 1 commit
    • Alexey Kardashevskiy's avatar
      powerpc: Prepare to support kernel handling of IOMMU map/unmap · 8e0861fa
      Alexey Kardashevskiy authored
      
      
      The current VFIO-on-POWER implementation supports only user mode
      driven mapping, i.e. QEMU is sending requests to map/unmap pages.
      However this approach is really slow, so we want to move that to KVM.
      Since H_PUT_TCE can be extremely performance sensitive (especially with
      network adapters where each packet needs to be mapped/unmapped) we chose
      to implement that as a "fast" hypercall directly in "real
      mode" (processor still in the guest context but MMU off).
      
      To be able to do that, we need to provide some facilities to
      access the struct page count within that real mode environment as things
      like the sparsemem vmemmap mappings aren't accessible.
      
      This adds an API function realmode_pfn_to_page() to get page struct when
      MMU is off.
      
      This adds to MM a new function put_page_unless_one() which drops a page
      if counter is bigger than 1. It is going to be used when MMU is off
      (for example, real mode on PPC64) and we want to make sure that page
      release will not happen in real mode as it may crash the kernel in
      a horrible way.
      
      CONFIG_SPARSEMEM_VMEMMAP and CONFIG_FLATMEM are supported.
      
      Cc: linux-mm@kvack.org
      Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
      Cc: Andrew Morton <akpm@linux-foundation.org>
      Reviewed-by: default avatarPaul Mackerras <paulus@samba.org>
      Signed-off-by: default avatarPaul Mackerras <paulus@samba.org>
      Signed-off-by: default avatarAlexey Kardashevskiy <aik@ozlabs.ru>
      Signed-off-by: default avatarBenjamin Herrenschmidt <benh@kernel.crashing.org>
      8e0861fa
  7. 09 Oct, 2013 3 commits
    • Peter Zijlstra's avatar
      sched/numa: Use {cpu, pid} to create task groups for shared faults · 8c8a743c
      Peter Zijlstra authored
      
      
      While parallel applications tend to align their data on the cache
      boundary, they tend not to align on the page or THP boundary.
      Consequently tasks that partition their data can still "false-share"
      pages presenting a problem for optimal NUMA placement.
      
      This patch uses NUMA hinting faults to chain tasks together into
      numa_groups. As well as storing the NID a task was running on when
      accessing a page a truncated representation of the faulting PID is
      stored. If subsequent faults are from different PIDs it is reasonable
      to assume that those two tasks share a page and are candidates for
      being grouped together. Note that this patch makes no scheduling
      decisions based on the grouping information.
      
      Signed-off-by: default avatarPeter Zijlstra <peterz@infradead.org>
      Signed-off-by: default avatarMel Gorman <mgorman@suse.de>
      Reviewed-by: default avatarRik van Riel <riel@redhat.com>
      Cc: Andrea Arcangeli <aarcange@redhat.com>
      Cc: Johannes Weiner <hannes@cmpxchg.org>
      Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
      Link: http://lkml.kernel.org/r/1381141781-10992-44-git-send-email-mgorman@suse.de
      
      
      Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
      8c8a743c
    • Peter Zijlstra's avatar
      mm: numa: Change page last {nid,pid} into {cpu,pid} · 90572890
      Peter Zijlstra authored
      
      
      Change the per page last fault tracking to use cpu,pid instead of
      nid,pid. This will allow us to try and lookup the alternate task more
      easily. Note that even though it is the cpu that is store in the page
      flags that the mpol_misplaced decision is still based on the node.
      
      Signed-off-by: default avatarPeter Zijlstra <peterz@infradead.org>
      Signed-off-by: default avatarMel Gorman <mgorman@suse.de>
      Reviewed-by: default avatarRik van Riel <riel@redhat.com>
      Cc: Andrea Arcangeli <aarcange@redhat.com>
      Cc: Johannes Weiner <hannes@cmpxchg.org>
      Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
      Link: http://lkml.kernel.org/r/1381141781-10992-43-git-send-email-mgorman@suse.de
      
      
      [ Fixed build failure on 32-bit systems. ]
      Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
      90572890
    • Mel Gorman's avatar
      sched/numa: Set preferred NUMA node based on number of private faults · b795854b
      Mel Gorman authored
      
      
      Ideally it would be possible to distinguish between NUMA hinting faults that
      are private to a task and those that are shared. If treated identically
      there is a risk that shared pages bounce between nodes depending on
      the order they are referenced by tasks. Ultimately what is desirable is
      that task private pages remain local to the task while shared pages are
      interleaved between sharing tasks running on different nodes to give good
      average performance. This is further complicated by THP as even
      applications that partition their data may not be partitioning on a huge
      page boundary.
      
      To start with, this patch assumes that multi-threaded or multi-process
      applications partition their data and that in general the private accesses
      are more important for cpu->memory locality in the general case. Also,
      no new infrastructure is required to treat private pages properly but
      interleaving for shared pages requires additional infrastructure.
      
      To detect private accesses the pid of the last accessing task is required
      but the storage requirements are a high. This patch borrows heavily from
      Ingo Molnar's patch "numa, mm, sched: Implement last-CPU+PID hash tracking"
      to encode some bits from the last accessing task in the page flags as
      well as the node information. Collisions will occur but it is better than
      just depending on the node information. Node information is then used to
      determine if a page needs to migrate. The PID information is used to detect
      private/shared accesses. The preferred NUMA node is selected based on where
      the maximum number of approximately private faults were measured. Shared
      faults are not taken into consideration for a few reasons.
      
      First, if there are many tasks sharing the page then they'll all move
      towards the same node. The node will be compute overloaded and then
      scheduled away later only to bounce back again. Alternatively the shared
      tasks would just bounce around nodes because the fault information is
      effectively noise. Either way accounting for shared faults the same as
      private faults can result in lower performance overall.
      
      The second reason is based on a hypothetical workload that has a small
      number of very important, heavily accessed private pages but a large shared
      array. The shared array would dominate the number of faults and be selected
      as a preferred node even though it's the wrong decision.
      
      The third reason is that multiple threads in a process will race each
      other to fault the shared page making the fault information unreliable.
      
      Signed-off-by: default avatarMel Gorman <mgorman@suse.de>
      [ Fix complication error when !NUMA_BALANCING. ]
      Reviewed-by: default avatarRik van Riel <riel@redhat.com>
      Cc: Andrea Arcangeli <aarcange@redhat.com>
      Cc: Johannes Weiner <hannes@cmpxchg.org>
      Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
      Signed-off-by: default avatarPeter Zijlstra <peterz@infradead.org>
      Link: http://lkml.kernel.org/r/1381141781-10992-30-git-send-email-mgorman@suse.de
      
      
      Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
      b795854b
  8. 12 Sep, 2013 3 commits
  9. 11 Sep, 2013 3 commits
    • Wanpeng Li's avatar
      mm/hwpoison: don't need to hold compound lock for hugetlbfs page · f9121153
      Wanpeng Li authored
      compound lock is introduced by commit e9da73d6
      
      ("thp: compound_lock."), it
      is used to serialize put_page against __split_huge_page_refcount().  In
      addition, transparent hugepages will be splitted in hwpoison handler and
      just one subpage will be poisoned.  There is unnecessary to hold compound
      lock for hugetlbfs page.  This patch replace compound_trans_order by
      compond_order in the place where the page is hugetlbfs page.
      
      Signed-off-by: default avatarWanpeng Li <liwanp@linux.vnet.ibm.com>
      Reviewed-by: default avatarNaoya Horiguchi <n-horiguchi@ah.jp.nec.com>
      Cc: Andi Kleen <andi@firstfloor.org>
      Cc: Tony Luck <tony.luck@intel.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      f9121153
    • Vlastimil Babka's avatar
      mm: munlock: manual pte walk in fast path instead of follow_page_mask() · 7a8010cd
      Vlastimil Babka authored
      
      
      Currently munlock_vma_pages_range() calls follow_page_mask() to obtain
      each individual struct page.  This entails repeated full page table
      translations and page table lock taken for each page separately.
      
      This patch avoids the costly follow_page_mask() where possible, by
      iterating over ptes within single pmd under single page table lock.  The
      first pte is obtained by get_locked_pte() for non-THP page acquired by the
      initial follow_page_mask().  The rest of the on-stack pagevec for munlock
      is filled up using pte_walk as long as pte_present() and vm_normal_page()
      are sufficient to obtain the struct page.
      
      After this patch, a 14% speedup was measured for munlocking a 56GB large
      memory area with THP disabled.
      
      Signed-off-by: default avatarVlastimil Babka <vbabka@suse.cz>
      Cc: Jörn Engel <joern@logfs.org>
      Cc: Mel Gorman <mgorman@suse.de>
      Cc: Michel Lespinasse <walken@google.com>
      Cc: Hugh Dickins <hughd@google.com>
      Cc: Rik van Riel <riel@redhat.com>
      Cc: Johannes Weiner <hannes@cmpxchg.org>
      Cc: Michal Hocko <mhocko@suse.cz>
      Cc: Vlastimil Babka <vbabka@suse.cz>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      7a8010cd
    • Cyrill Gorcunov's avatar
      mm: track vma changes with VM_SOFTDIRTY bit · d9104d1c
      Cyrill Gorcunov authored
      
      
      Pavel reported that in case if vma area get unmapped and then mapped (or
      expanded) in-place, the soft dirty tracker won't be able to recognize this
      situation since it works on pte level and ptes are get zapped on unmap,
      loosing soft dirty bit of course.
      
      So to resolve this situation we need to track actions on vma level, there
      VM_SOFTDIRTY flag comes in.  When new vma area created (or old expanded)
      we set this bit, and keep it here until application calls for clearing
      soft dirty bit.
      
      Thus when user space application track memory changes now it can detect if
      vma area is renewed.
      
      Reported-by: default avatarPavel Emelyanov <xemul@parallels.com>
      Signed-off-by: default avatarCyrill Gorcunov <gorcunov@openvz.org>
      Cc: Andy Lutomirski <luto@amacapital.net>
      Cc: Matt Mackall <mpm@selenic.com>
      Cc: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
      Cc: Marcelo Tosatti <mtosatti@redhat.com>
      Cc: KOSAKI Motohiro <kosaki.motohiro@gmail.com>
      Cc: Stephen Rothwell <sfr@canb.auug.org.au>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
      Cc: Rob Landley <rob@landley.net>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      d9104d1c
  10. 10 Jul, 2013 1 commit
  11. 09 Jul, 2013 1 commit
  12. 03 Jul, 2013 7 commits
    • Jiang Liu's avatar
      mm: introduce helper function set_max_mapnr() · fccc9987
      Jiang Liu authored
      
      
      Introduce a helper function set_max_mapnr() to set global variable
      max_mapnr.
      
      Also unify condition compilation for max_mapnr with
      CONFIG_NEED_MULTIPLE_NODES instead of CONFIG_DISCONTIGMEM.
      
      Signed-off-by: default avatarJiang Liu <jiang.liu@huawei.com>
      Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
      Cc: Mauro Carvalho Chehab <mchehab@redhat.com>
      Cc: "David S. Miller" <davem@davemloft.net>
      Cc: Mark Brown <broonie@opensource.wolfsonmicro.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      fccc9987
    • Jiang Liu's avatar
      mm: kill global variable num_physpages · 18954181
      Jiang Liu authored
      
      
      Now all references to num_physpages have been removed, so kill it.
      
      Signed-off-by: default avatarJiang Liu <jiang.liu@huawei.com>
      Cc: Mel Gorman <mgorman@suse.de>
      Cc: Michel Lespinasse <walken@google.com>
      Cc: Rik van Riel <riel@redhat.com>
      Cc: Jiang Liu <jiang.liu@huawei.com>
      Cc: Hugh Dickins <hughd@google.com>
      Cc: David Rientjes <rientjes@google.com>
      Cc: Al Viro <viro@zeniv.linux.org.uk>
      Cc: Konstantin Khlebnikov <khlebnikov@openvz.org>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      18954181
    • Jiang Liu's avatar
      mm: introduce helper function mem_init_print_info() to simplify mem_init() · 7ee3d4e8
      Jiang Liu authored
      
      
      Introduce helper function mem_init_print_info() to simplify mem_init()
      across different architectures, which also unifies the format and
      information printed.
      
      Function mem_init_print_info() calculates memory statistics information
      without walking each page, so it should be a little faster on some
      architectures.
      
      Also introduce another helper get_num_physpages() to kill the global
      variable num_physpages.
      
      Signed-off-by: default avatarJiang Liu <jiang.liu@huawei.com>
      Cc: Mel Gorman <mgorman@suse.de>
      Cc: Michel Lespinasse <walken@google.com>
      Cc: Rik van Riel <riel@redhat.com>
      Cc: Minchan Kim <minchan@kernel.org>
      Cc: Marek Szyprowski <m.szyprowski@samsung.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      7ee3d4e8
    • Jiang Liu's avatar
      mm: use a dedicated lock to protect totalram_pages and zone->managed_pages · c3d5f5f0
      Jiang Liu authored
      
      
      Currently lock_memory_hotplug()/unlock_memory_hotplug() are used to
      protect totalram_pages and zone->managed_pages.  Other than the memory
      hotplug driver, totalram_pages and zone->managed_pages may also be
      modified at runtime by other drivers, such as Xen balloon,
      virtio_balloon etc.  For those cases, memory hotplug lock is a little
      too heavy, so introduce a dedicated lock to protect totalram_pages and
      zone->managed_pages.
      
      Now we have a simplified locking rules totalram_pages and
      zone->managed_pages as:
      
      1) no locking for read accesses because they are unsigned long.
      2) no locking for write accesses at boot time in single-threaded context.
      3) serialize write accesses at runtime by acquiring the dedicated
         managed_page_count_lock.
      
      Also adjust zone->managed_pages when freeing reserved pages into the
      buddy system, to keep totalram_pages and zone->managed_pages in
      consistence.
      
      [akpm@linux-foundation.org: don't export adjust_managed_page_count to modules (for now)]
      Signed-off-by: default avatarJiang Liu <jiang.liu@huawei.com>
      Cc: Mel Gorman <mel@csn.ul.ie>
      Cc: Michel Lespinasse <walken@google.com>
      Cc: Rik van Riel <riel@redhat.com>
      Cc: Minchan Kim <minchan@kernel.org>
      Cc: "H. Peter Anvin" <hpa@zytor.com>
      Cc: "Michael S. Tsirkin" <mst@redhat.com>
      Cc: <sworddragon2@aol.com>
      Cc: Arnd Bergmann <arnd@arndb.de>
      Cc: Catalin Marinas <catalin.marinas@arm.com>
      Cc: Chris Metcalf <cmetcalf@tilera.com>
      Cc: David Howells <dhowells@redhat.com>
      Cc: Geert Uytterhoeven <geert@linux-m68k.org>
      Cc: Ingo Molnar <mingo@redhat.com>
      Cc: Jeremy Fitzhardinge <jeremy@goop.org>
      Cc: Jianguo Wu <wujianguo@huawei.com>
      Cc: Joonsoo Kim <js1304@gmail.com>
      Cc: Kamezawa Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
      Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
      Cc: Marek Szyprowski <m.szyprowski@samsung.com>
      Cc: Rusty Russell <rusty@rustcorp.com.au>
      Cc: Tang Chen <tangchen@cn.fujitsu.com>
      Cc: Tejun Heo <tj@kernel.org>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Cc: Wen Congyang <wency@cn.fujitsu.com>
      Cc: Will Deacon <will.deacon@arm.com>
      Cc: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
      Cc: Yinghai Lu <yinghai@kernel.org>
      Cc: Russell King <rmk@arm.linux.org.uk>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      c3d5f5f0
    • Jiang Liu's avatar
      mm: enhance free_reserved_area() to support poisoning memory with zero · dbe67df4
      Jiang Liu authored
      
      
      Address more review comments from last round of code review.
      1) Enhance free_reserved_area() to support poisoning freed memory with
         pattern '0'. This could be used to get rid of poison_init_mem()
         on ARM64.
      2) A previous patch has disabled memory poison for initmem on s390
         by mistake, so restore to the original behavior.
      3) Remove redundant PAGE_ALIGN() when calling free_reserved_area().
      
      Signed-off-by: default avatarJiang Liu <jiang.liu@huawei.com>
      Cc: Geert Uytterhoeven <geert@linux-m68k.org>
      Cc: "H. Peter Anvin" <hpa@zytor.com>
      Cc: "Michael S. Tsirkin" <mst@redhat.com>
      Cc: <sworddragon2@aol.com>
      Cc: Arnd Bergmann <arnd@arndb.de>
      Cc: Catalin Marinas <catalin.marinas@arm.com>
      Cc: Chris Metcalf <cmetcalf@tilera.com>
      Cc: David Howells <dhowells@redhat.com>
      Cc: Ingo Molnar <mingo@redhat.com>
      Cc: Jeremy Fitzhardinge <jeremy@goop.org>
      Cc: Jianguo Wu <wujianguo@huawei.com>
      Cc: Joonsoo Kim <js1304@gmail.com>
      Cc: Kamezawa Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
      Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
      Cc: Marek Szyprowski <m.szyprowski@samsung.com>
      Cc: Mel Gorman <mel@csn.ul.ie>
      Cc: Michel Lespinasse <walken@google.com>
      Cc: Minchan Kim <minchan@kernel.org>
      Cc: Rik van Riel <riel@redhat.com>
      Cc: Rusty Russell <rusty@rustcorp.com.au>
      Cc: Tang Chen <tangchen@cn.fujitsu.com>
      Cc: Tejun Heo <tj@kernel.org>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Cc: Wen Congyang <wency@cn.fujitsu.com>
      Cc: Will Deacon <will.deacon@arm.com>
      Cc: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
      Cc: Yinghai Lu <yinghai@kernel.org>
      Cc: Russell King <rmk@arm.linux.org.uk>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      dbe67df4
    • Jiang Liu's avatar
      mm: change signature of free_reserved_area() to fix building warnings · 11199692
      Jiang Liu authored
      
      
      Change signature of free_reserved_area() according to Russell King's
      suggestion to fix following build warnings:
      
        arch/arm/mm/init.c: In function 'mem_init':
        arch/arm/mm/init.c:603:2: warning: passing argument 1 of 'free_reserved_area' makes integer from pointer without a cast [enabled by default]
          free_reserved_area(__va(PHYS_PFN_OFFSET), swapper_pg_dir, 0, NULL);
          ^
        In file included from include/linux/mman.h:4:0,
                         from arch/arm/mm/init.c:15:
        include/linux/mm.h:1301:22: note: expected 'long unsigned int' but argument is of type 'void *'
         extern unsigned long free_reserved_area(unsigned long start, unsigned long end,
      
         mm/page_alloc.c: In function 'free_reserved_area':
      >> mm/page_alloc.c:5134:3: warning: passing argument 1 of 'virt_to_phys' makes pointer from integer without a cast [enabled by default]
         In file included from arch/mips/include/asm/page.h:49:0,
                          from include/linux/mmzone.h:20,
                          from include/linux/gfp.h:4,
                          from include/linux/mm.h:8,
                          from mm/page_alloc.c:18:
         arch/mips/include/asm/io.h:119:29: note: expected 'const volatile void *' but argument is of type 'long unsigned int'
         mm/page_alloc.c: In function 'free_area_init_nodes':
         mm/page_alloc.c:5030:34: warning: array subscript is below array bounds [-Warray-bounds]
      
      Also address some minor code review comments.
      
      Signed-off-by: default avatarJiang Liu <jiang.liu@huawei.com>
      Reported-by: default avatarArnd Bergmann <arnd@arndb.de>
      Cc: "H. Peter Anvin" <hpa@zytor.com>
      Cc: "Michael S. Tsirkin" <mst@redhat.com>
      Cc: <sworddragon2@aol.com>
      Cc: Catalin Marinas <catalin.marinas@arm.com>
      Cc: Chris Metcalf <cmetcalf@tilera.com>
      Cc: David Howells <dhowells@redhat.com>
      Cc: Geert Uytterhoeven <geert@linux-m68k.org>
      Cc: Ingo Molnar <mingo@redhat.com>
      Cc: Jeremy Fitzhardinge <jeremy@goop.org>
      Cc: Jianguo Wu <wujianguo@huawei.com>
      Cc: Joonsoo Kim <js1304@gmail.com>
      Cc: Kamezawa Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
      Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
      Cc: Marek Szyprowski <m.szyprowski@samsung.com>
      Cc: Mel Gorman <mel@csn.ul.ie>
      Cc: Michel Lespinasse <walken@google.com>
      Cc: Minchan Kim <minchan@kernel.org>
      Cc: Rik van Riel <riel@redhat.com>
      Cc: Rusty Russell <rusty@rustcorp.com.au>
      Cc: Tang Chen <tangchen@cn.fujitsu.com>
      Cc: Tejun Heo <tj@kernel.org>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Cc: Wen Congyang <wency@cn.fujitsu.com>
      Cc: Will Deacon <will.deacon@arm.com>
      Cc: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
      Cc: Yinghai Lu <yinghai@kernel.org>
      Cc: Russell King <rmk@arm.linux.org.uk>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      11199692
    • Andrew Morton's avatar
      include/linux/mm.h: add PAGE_ALIGNED() helper · 0fa73b86
      Andrew Morton authored
      
      
      To test whether an address is aligned to PAGE_SIZE.
      
      Cc: HATAYAMA Daisuke <d.hatayama@jp.fujitsu.com>
      Cc: "Eric W. Biederman" <ebiederm@xmission.com>,
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      0fa73b86
  13. 22 May, 2013 1 commit
    • Lukas Czerner's avatar
      mm: change invalidatepage prototype to accept length · d47992f8
      Lukas Czerner authored
      
      
      Currently there is no way to truncate partial page where the end
      truncate point is not at the end of the page. This is because it was not
      needed and the functionality was enough for file system truncate
      operation to work properly. However more file systems now support punch
      hole feature and it can benefit from mm supporting truncating page just
      up to the certain point.
      
      Specifically, with this functionality truncate_inode_pages_range() can
      be changed so it supports truncating partial page at the end of the
      range (currently it will BUG_ON() if 'end' is not at the end of the
      page).
      
      This commit changes the invalidatepage() address space operation
      prototype to accept range to be invalidated and update all the instances
      for it.
      
      We also change the block_invalidatepage() in the same way and actually
      make a use of the new length argument implementing range invalidation.
      
      Actual file system implementations will follow except the file systems
      where the changes are really simple and should not change the behaviour
      in any way .Implementation for truncate_page_range() which will be able
      to accept page unaligned ranges will follow as well.
      
      Signed-off-by: default avatarLukas Czerner <lczerner@redhat.com>
      Cc: Andrew Morton <akpm@linux-foundation.org>
      Cc: Hugh Dickins <hughd@google.com>
      d47992f8
  14. 08 May, 2013 1 commit
  15. 29 Apr, 2013 6 commits
    • Andrew Shewmaker's avatar
      mm: replace hardcoded 3% with admin_reserve_pages knob · 4eeab4f5
      Andrew Shewmaker authored
      
      
      Add an admin_reserve_kbytes knob to allow admins to change the hardcoded
      memory reserve to something other than 3%, which may be multiple
      gigabytes on large memory systems.  Only about 8MB is necessary to
      enable recovery in the default mode, and only a few hundred MB are
      required even when overcommit is disabled.
      
      This affects OVERCOMMIT_GUESS and OVERCOMMIT_NEVER.
      
      admin_reserve_kbytes is initialized to min(3% free pages, 8MB)
      
      I arrived at 8MB by summing the RSS of sshd or login, bash, and top.
      
      Please see first patch in this series for full background, motivation,
      testing, and full changelog.
      
      [akpm@linux-foundation.org: coding-style fixes]
      [akpm@linux-foundation.org: make init_admin_reserve() static]
      Signed-off-by: default avatarAndrew Shewmaker <agshew@gmail.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      4eeab4f5
    • Andrew Shewmaker's avatar
      mm: limit growth of 3% hardcoded other user reserve · c9b1d098
      Andrew Shewmaker authored
      
      
      Add user_reserve_kbytes knob.
      
      Limit the growth of the memory reserved for other user processes to
      min(3% current process size, user_reserve_pages).  Only about 8MB is
      necessary to enable recovery in the default mode, and only a few hundred
      MB are required even when overcommit is disabled.
      
      user_reserve_pages defaults to min(3% free pages, 128MB)
      
      I arrived at 128MB by taking the max VSZ of sshd, login, bash, and top ...
      then adding the RSS of each.
      
      This only affects OVERCOMMIT_NEVER mode.
      
      Background
      
      1. user reserve
      
      __vm_enough_memory reserves a hardcoded 3% of the current process size for
      other applications when overcommit is disabled.  This was done so that a
      user could recover if they launched a memory hogging process.  Without the
      reserve, a user would easily run into a message such as:
      
      bash: fork: Cannot allocate memory
      
      2. admin reserve
      
      Additionally, a hardcoded 3% of free memory is reserved for root in both
      overcommit 'guess' and 'never' modes.  This was intended to prevent a
      scenario where root-cant-log-in and perform recovery operations.
      
      Note that this reserve shrinks, and doesn't guarantee a useful reserve.
      
      Motivation
      
      The two hardcoded memory reserves should be updated to account for current
      memory sizes.
      
      Also, the admin reserve would be more useful if it didn't shrink too much.
      
      When the current code was originally written, 1GB was considered
      "enterprise".  Now the 3% reserve can grow to multiple GB on large memory
      systems, and it only needs to be a few hundred MB at most to enable a user
      or admin to recover a system with an unwanted memory hogging process.
      
      I've found that reducing these reserves is especially beneficial for a
      specific type of application load:
      
       * single application system
       * one or few processes (e.g. one per core)
       * allocating all available memory
       * not initializing every page immediately
       * long running
      
      I've run scientific clusters with this sort of load.  A long running job
      sometimes failed many hours (weeks of CPU time) into a calculation.  They
      weren't initializing all of their memory immediately, and they weren't
      using calloc, so I put systems into overcommit 'never' mode.  These
      clusters run diskless and have no swap.
      
      However, with the current reserves, a user wishing to allocate as much
      memory as possible to one process may be prevented from using, for
      example, almost 2GB out of 32GB.
      
      The effect is less, but still significant when a user starts a job with
      one process per core.  I have repeatedly seen a set of processes
      requesting the same amount of memory fail because one of them could not
      allocate the amount of memory a user would expect to be able to allocate.
      For example, Message Passing Interfce (MPI) processes, one per core.  And
      it is similar for other parallel programming frameworks.
      
      Changing this reserve code will make the overcommit never mode more useful
      by allowing applications to allocate nearly all of the available memory.
      
      Also, the new admin_reserve_kbytes will be safer than the current behavior
      since the hardcoded 3% of available memory reserve can shrink to something
      useless in the case where applications have grabbed all available memory.
      
      Risks
      
      * "bash: fork: Cannot allocate memory"
      
        The downside of the first patch-- which creates a tunable user reserve
        that is only used in overcommit 'never' mode--is that an admin can set
        it so low that a user may not be able to kill their process, even if
        they already have a shell prompt.
      
        Of course, a user can get in the same predicament with the current 3%
        reserve--they just have to launch processes until 3% becomes negligible.
      
      * root-cant-log-in problem
      
        The second patch, adding the tunable rootuser_reserve_pages, allows
        the admin to shoot themselves in the foot by setting it too small.  They
        can easily get the system into a state where root-can't-log-in.
      
        However, the new admin_reserve_kbytes will be safer than the current
        behavior since the hardcoded 3% of available memory reserve can shrink
        to something useless in the case where applications have grabbed all
        available memory.
      
      Alternatives
      
       * Memory cgroups provide a more flexible way to limit application memory.
      
         Not everyone wants to set up cgroups or deal with their overhead.
      
       * We could create a fourth overcommit mode which provides smaller reserves.
      
         The size of useful reserves may be drastically different depending
         on the whether the system is embedded or enterprise.
      
       * Force users to initialize all of their memory or use calloc.
      
         Some users don't want/expect the system to overcommit when they malloc.
         Overcommit 'never' mode is for this scenario, and it should work well.
      
      The new user and admin reserve tunables are simple to use, with low
      overhead compared to cgroups.  The patches preserve current behavior where
      3% of memory is less than 128MB, except that the admin reserve doesn't
      shrink to an unusable size under pressure.  The code allows admins to tune
      for embedded and enterprise usage.
      
      FAQ
      
       * How is the root-cant-login problem addressed?
         What happens if admin_reserve_pages is set to 0?
      
         Root is free to shoot themselves in the foot by setting
         admin_reserve_kbytes too low.
      
         On x86_64, the minimum useful reserve is:
           8MB for overcommit 'guess'
         128MB for overcommit 'never'
      
         admin_reserve_pages defaults to min(3% free memory, 8MB)
      
         So, anyone switching to 'never' mode needs to adjust
         admin_reserve_pages.
      
       * How do you calculate a minimum useful reserve?
      
         A user or the admin needs enough memory to login and perform
         recovery operations, which includes, at a minimum:
      
         sshd or login + bash (or some other shell) + top (or ps, kill, etc.)
      
         For overcommit 'guess', we can sum resident set sizes (RSS)
         because we only need enough memory to handle what the recovery
         programs will typically use. On x86_64 this is about 8MB.
      
         For overcommit 'never', we can take the max of their virtual sizes (VSZ)
         and add the sum of their RSS. We use VSZ instead of RSS because mode
         forces us to ensure we can fulfill all of the requested memory allocations--
         even if the programs only use a fraction of what they ask for.
         On x86_64 this is about 128MB.
      
         When swap is enabled, reserves are useful even when they are as
         small as 10MB, regardless of overcommit mode.
      
         When both swap and overcommit are disabled, then the admin should
         tune the reserves higher to be absolutley safe. Over 230MB each
         was safest in my testing.
      
       * What happens if user_reserve_pages is set to 0?
      
         Note, this only affects overcomitt 'never' mode.
      
         Then a user will be able to allocate all available memory minus
         admin_reserve_kbytes.
      
         However, they will easily see a message such as:
      
         "bash: fork: Cannot allocate memory"
      
         And they won't be able to recover/kill their application.
         The admin should be able to recover the system if
         admin_reserve_kbytes is set appropriately.
      
       * What's the difference between overcommit 'guess' and 'never'?
      
         "Guess" allows an allocation if there are enough free + reclaimable
         pages. It has a hardcoded 3% of free pages reserved for root.
      
         "Never" allows an allocation if there is enough swap + a configurable
         percentage (default is 50) of physical RAM. It has a hardcoded 3% of
         free pages reserved for root, like "Guess" mode. It also has a
         hardcoded 3% of the current process size reserved for additional
         applications.
      
       * Why is overcommit 'guess' not suitable even when an app eventually
         writes to every page? It takes free pages, file pages, available
         swap pages, reclaimable slab pages into consideration. In other words,
         these are all pages available, then why isn't overcommit suitable?
      
         Because it only looks at the present state of the system. It
         does not take into account the memory that other applications have
         malloced, but haven't initialized yet. It overcommits the system.
      
      Test Summary
      
      There was little change in behavior in the default overcommit 'guess'
      mode with swap enabled before and after the patch. This was expected.
      
      Systems run most predictably (i.e. no oom kills) in overcommit 'never'
      mode with swap enabled. This also allowed the most memory to be allocated
      to a user application.
      
      Overcommit 'guess' mode without swap is a bad idea. It is easy to
      crash the system. None of the other tested combinations crashed.
      This matches my experience on the Roadrunner supercomputer.
      
      Without the tunable user reserve, a system in overcommit 'never' mode
      and without swap does not allow the admin to recover, although the
      admin can.
      
      With the new tunable reserves, a system in overcommit 'never' mode
      and without swap can be configured to:
      
      1. maximize user-allocatable memory, running close to the edge of
      recoverability
      
      2. maximize recoverability, sacrificing allocatable memory to
      ensure that a user cannot take down a system
      
      Test Description
      
      Fedora 18 VM - 4 x86_64 cores, 5725MB RAM, 4GB Swap
      
      System is booted into multiuser console mode, with unnecessary services
      turned off. Caches were dropped before each test.
      
      Hogs are user memtester processes that attempt to allocate all free memory
      as reported by /proc/meminfo
      
      In overcommit 'never' mode, memory_ratio=100
      
      Test Results
      
      3.9.0-rc1-mm1
      
      Overcommit | Swap | Hogs | MB Got/Wanted | OOMs | User Recovery | Admin Recovery
      ----------   ----   ----   -------------   ----   -------------   --------------
      guess        yes    1      5432/5432       no     yes             yes
      guess        yes    4      5444/5444       1      yes             yes
      guess        no     1      5302/5449       no     yes             yes
      guess        no     4      -               crash  no              no
      
      never        yes    1      5460/5460       1      yes             yes
      never        yes    4      5460/5460       1      yes             yes
      never        no     1      5218/5432       no     no              yes
      never        no     4      5203/5448       no     no              yes
      
      3.9.0-rc1-mm1-tunablereserves
      
      User and Admin Recovery show their respective reserves, if applicable.
      
      Overcommit | Swap | Hogs | MB Got/Wanted | OOMs | User Recovery | Admin Recovery
      ----------   ----   ----   -------------   ----   -------------   --------------
      guess        yes    1      5419/5419       no     - yes           8MB yes
      guess        yes    4      5436/5436       1      - yes           8MB yes
      guess        no     1      5440/5440       *      - yes           8MB yes
      guess        no     4      -               crash  - no            8MB no
      
      * process would successfully mlock, then the oom killer would pick it
      
      never        yes    1      5446/5446       no     10MB yes        20MB yes
      never        yes    4      5456/5456       no     10MB yes        20MB yes
      never        no     1      5387/5429       no     128MB no        8MB barely
      never        no     1      5323/5428       no     226MB barely    8MB barely
      never        no     1      5323/5428       no     226MB barely    8MB barely
      
      never        no     1      5359/5448       no     10MB no         10MB barely
      
      never        no     1      5323/5428       no     0MB no          10MB barely
      never        no     1      5332/5428       no     0MB no          50MB yes
      never        no     1      5293/5429       no     0MB no          90MB yes
      
      never        no     1      5001/5427       no     230MB yes       338MB yes
      never        no     4*     4998/5424       no     230MB yes       338MB yes
      
      * more memtesters were launched, able to allocate approximately another 100MB
      
      Future Work
      
       - Test larger memory systems.
      
       - Test an embedded image.
      
       - Test other architectures.
      
       - Time malloc microbenchmarks.
      
       - Would it be useful to be able to set overcommit policy for
         each memory cgroup?
      
       - Some lines are slightly above 80 chars.
         Perhaps define a macro to convert between pages and kb?
         Other places in the kernel do this.
      
      [akpm@linux-foundation.org: coding-style fixes]
      [akpm@linux-foundation.org: make init_user_reserve() static]
      Signed-off-by: default avatarAndrew Shewmaker <agshew@gmail.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      c9b1d098
    • Cody P Schafer's avatar
      page_alloc: make setup_nr_node_ids() usable for arch init code · f9872caf
      Cody P Schafer authored
      
      
      powerpc and x86 were opencoding copies of setup_nr_node_ids(), which
      page_alloc provides but makes static.  Make it avaliable to the archs in
      linux/mm.h.
      
      Signed-off-by: default avatarCody P Schafer <cody@linux.vnet.ibm.com>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      f9872caf
    • Johannes Weiner's avatar
      sparse-vmemmap: specify vmemmap population range in bytes · 0aad818b
      Johannes Weiner authored
      
      
      The sparse code, when asking the architecture to populate the vmemmap,
      specifies the section range as a starting page and a number of pages.
      
      This is an awkward interface, because none of the arch-specific code
      actually thinks of the range in terms of 'struct page' units and always
      translates it to bytes first.
      
      In addition, later patches mix huge page and regular page backing for
      the vmemmap.  For this, they need to call vmemmap_populate_basepages()
      on sub-section ranges with PAGE_SIZE and PMD_SIZE in mind.  But these
      are not necessarily multiples of the 'struct page' size and so this unit
      is too coarse.
      
      Just translate the section range into bytes once in the generic sparse
      code, then pass byte ranges down the stack.
      
      Signed-off-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
      Cc: Ben Hutchings <ben@decadent.org.uk>
      Cc: Bernhard Schmidt <Bernhard.Schmidt@lrz.de>
      Cc: Johannes Weiner <hannes@cmpxchg.org>
      Cc: Russell King <rmk@arm.linux.org.uk>
      Cc: Ingo Molnar <mingo@elte.hu>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Cc: "H. Peter Anvin" <hpa@zytor.com>
      Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
      Cc: "Luck, Tony" <tony.luck@intel.com>
      Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
      Acked-by: default avatarDavid S. Miller <davem@davemloft.net>
      Tested-by: default avatarDavid S. Miller <davem@davemloft.net>
      Cc: Wu Fengguang <fengguang.wu@intel.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      0aad818b
    • Josh Triplett's avatar
      fs: don't compile in drop_caches.c when CONFIG_SYSCTL=n · 146732ce
      Josh Triplett authored
      
      
      drop_caches.c provides code only invokable via sysctl, so don't compile it
      in when CONFIG_SYSCTL=n.
      
      Signed-off-by: default avatarJosh Triplett <josh@joshtriplett.org>
      Acked-by: default avatarKees Cook <keescook@chromium.org>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      146732ce
    • Jiang Liu's avatar
      mm: introduce free_highmem_page() helper to free highmem pages into buddy system · cfa11e08
      Jiang Liu authored
      The original goal of this patchset is to fix the bug reported by
      
        https://bugzilla.kernel.org/show_bug.cgi?id=53501
      
      Now it has also been expanded to reduce common code used by memory
      initializion.
      
      This is the second part, which applies to the previous part at:
        http://marc.info/?l=linux-mm&m=136289696323825&w=2
      
      
      
      It introduces a helper function free_highmem_page() to free highmem
      pages into the buddy system when initializing mm subsystem.
      Introduction of free_highmem_page() is one step forward to clean up
      accesses and modificaitons of totalhigh_pages, totalram_pages and
      zone->managed_pages etc. I hope we could remove all references to
      totalhigh_pages from the arch/ subdirectory.
      
      We have only tested these patchset on x86 platforms, and have done basic
      compliation tests using cross-compilers from ftp.kernel.org. That means
      some code may not pass compilation on some architectures. So any help
      to test this patchset are welcomed!
      
      There are several other parts still under development:
      Part3: refine code to manage totalram_pages, totalhigh_pages and
      	zone->managed_pages
      Part4: introduce helper functions to simplify mem_init() and remove the
      	global variable num_physpages.
      
      This patch:
      
      Introduce helper function free_highmem_page(), which will be used by
      architectures with HIGHMEM enabled to free highmem pages into the buddy
      system.
      
      Signed-off-by: default avatarJiang Liu <jiang.liu@huawei.com>
      Cc: "David S. Miller" <davem@davemloft.net>
      Cc: "H. Peter Anvin" <hpa@zytor.com>
      Cc: "Suzuki K. Poulose" <suzuki@in.ibm.com>
      Cc: Alexander Graf <agraf@suse.de>
      Cc: Arnd Bergmann <arnd@arndb.de>
      Cc: Attilio Rao <attilio.rao@citrix.com>
      Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
      Cc: Cong Wang <amwang@redhat.com>
      Cc: David Daney <david.daney@cavium.com>
      Cc: David Howells <dhowells@redhat.com>
      Cc: Geert Uytterhoeven <geert@linux-m68k.org>
      Cc: Ingo Molnar <mingo@redhat.com>
      Cc: James Hogan <james.hogan@imgtec.com>
      Cc: Jeff Dike <jdike@addtoit.com>
      Cc: Jiang Liu <jiang.liu@huawei.com>
      Cc: Jiang Liu <liuj97@gmail.com>
      Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
      Cc: Konstantin Khlebnikov <khlebnikov@openvz.org>
      Cc: Linus Walleij <linus.walleij@linaro.org>
      Cc: Marek Szyprowski <m.szyprowski@samsung.com>
      Cc: Mel Gorman <mgorman@suse.de>
      Cc: Michal Nazarewicz <mina86@mina86.com>
      Cc: Michal Simek <monstr@monstr.eu>
      Cc: Michel Lespinasse <walken@google.com>
      Cc: Minchan Kim <minchan@kernel.org>
      Cc: Paul Mackerras <paulus@samba.org>
      Cc: Ralf Baechle <ralf@linux-mips.org>
      Cc: Richard Weinberger <richard@nod.at>
      Cc: Rik van Riel <riel@redhat.com>
      Cc: Russell King <linux@arm.linux.org.uk>
      Cc: Sam Ravnborg <sam@ravnborg.org>
      Cc: Stephen Boyd <sboyd@codeaurora.org>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Cc: Yinghai Lu <yinghai@kernel.org>
      Reviewed-by: default avatarPekka Enberg <penberg@kernel.org>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      cfa11e08