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32 results

mmzone.h

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    • Mel Gorman's avatar
      2a1e274a
      Create the ZONE_MOVABLE zone · 2a1e274a
      Mel Gorman authored
      
      The following 8 patches against 2.6.20-mm2 create a zone called ZONE_MOVABLE
      that is only usable by allocations that specify both __GFP_HIGHMEM and
      __GFP_MOVABLE.  This has the effect of keeping all non-movable pages within a
      single memory partition while allowing movable allocations to be satisfied
      from either partition.  The patches may be applied with the list-based
      anti-fragmentation patches that groups pages together based on mobility.
      
      The size of the zone is determined by a kernelcore= parameter specified at
      boot-time.  This specifies how much memory is usable by non-movable
      allocations and the remainder is used for ZONE_MOVABLE.  Any range of pages
      within ZONE_MOVABLE can be released by migrating the pages or by reclaiming.
      
      When selecting a zone to take pages from for ZONE_MOVABLE, there are two
      things to consider.  First, only memory from the highest populated zone is
      used for ZONE_MOVABLE.  On the x86, this is probably going to be ZONE_HIGHMEM
      but it would be ZONE_DMA on ppc64 or possibly ZONE_DMA32 on x86_64.  Second,
      the amount of memory usable by the kernel will be spread evenly throughout
      NUMA nodes where possible.  If the nodes are not of equal size, the amount of
      memory usable by the kernel on some nodes may be greater than others.
      
      By default, the zone is not as useful for hugetlb allocations because they are
      pinned and non-migratable (currently at least).  A sysctl is provided that
      allows huge pages to be allocated from that zone.  This means that the huge
      page pool can be resized to the size of ZONE_MOVABLE during the lifetime of
      the system assuming that pages are not mlocked.  Despite huge pages being
      non-movable, we do not introduce additional external fragmentation of note as
      huge pages are always the largest contiguous block we care about.
      
      Credit goes to Andy Whitcroft for catching a large variety of problems during
      review of the patches.
      
      This patch creates an additional zone, ZONE_MOVABLE.  This zone is only usable
      by allocations which specify both __GFP_HIGHMEM and __GFP_MOVABLE.  Hot-added
      memory continues to be placed in their existing destination as there is no
      mechanism to redirect them to a specific zone.
      
      [y-goto@jp.fujitsu.com: Fix section mismatch of memory hotplug related code]
      [akpm@linux-foundation.org: various fixes]
      Signed-off-by: default avatarMel Gorman <mel@csn.ul.ie>
      Cc: Andy Whitcroft <apw@shadowen.org>
      Signed-off-by: default avatarYasunori Goto <y-goto@jp.fujitsu.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>
      2a1e274a
      History
      Create the ZONE_MOVABLE zone
      Mel Gorman authored
      
      The following 8 patches against 2.6.20-mm2 create a zone called ZONE_MOVABLE
      that is only usable by allocations that specify both __GFP_HIGHMEM and
      __GFP_MOVABLE.  This has the effect of keeping all non-movable pages within a
      single memory partition while allowing movable allocations to be satisfied
      from either partition.  The patches may be applied with the list-based
      anti-fragmentation patches that groups pages together based on mobility.
      
      The size of the zone is determined by a kernelcore= parameter specified at
      boot-time.  This specifies how much memory is usable by non-movable
      allocations and the remainder is used for ZONE_MOVABLE.  Any range of pages
      within ZONE_MOVABLE can be released by migrating the pages or by reclaiming.
      
      When selecting a zone to take pages from for ZONE_MOVABLE, there are two
      things to consider.  First, only memory from the highest populated zone is
      used for ZONE_MOVABLE.  On the x86, this is probably going to be ZONE_HIGHMEM
      but it would be ZONE_DMA on ppc64 or possibly ZONE_DMA32 on x86_64.  Second,
      the amount of memory usable by the kernel will be spread evenly throughout
      NUMA nodes where possible.  If the nodes are not of equal size, the amount of
      memory usable by the kernel on some nodes may be greater than others.
      
      By default, the zone is not as useful for hugetlb allocations because they are
      pinned and non-migratable (currently at least).  A sysctl is provided that
      allows huge pages to be allocated from that zone.  This means that the huge
      page pool can be resized to the size of ZONE_MOVABLE during the lifetime of
      the system assuming that pages are not mlocked.  Despite huge pages being
      non-movable, we do not introduce additional external fragmentation of note as
      huge pages are always the largest contiguous block we care about.
      
      Credit goes to Andy Whitcroft for catching a large variety of problems during
      review of the patches.
      
      This patch creates an additional zone, ZONE_MOVABLE.  This zone is only usable
      by allocations which specify both __GFP_HIGHMEM and __GFP_MOVABLE.  Hot-added
      memory continues to be placed in their existing destination as there is no
      mechanism to redirect them to a specific zone.
      
      [y-goto@jp.fujitsu.com: Fix section mismatch of memory hotplug related code]
      [akpm@linux-foundation.org: various fixes]
      Signed-off-by: default avatarMel Gorman <mel@csn.ul.ie>
      Cc: Andy Whitcroft <apw@shadowen.org>
      Signed-off-by: default avatarYasunori Goto <y-goto@jp.fujitsu.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>
    hardware.h 4.13 KiB