• Bob Picco's avatar
    [PATCH] SPARSEMEM EXTREME · 802f192e
    Bob Picco authored
    A new option for SPARSEMEM is ARCH_SPARSEMEM_EXTREME.  Architecture
    platforms with a very sparse physical address space would likely want to
    select this option.  For those architecture platforms that don't select the
    option, the code generated is equivalent to SPARSEMEM currently in -mm.
    I'll be posting a patch on ia64 ml which uses this new SPARSEMEM feature.
    
    ARCH_SPARSEMEM_EXTREME makes mem_section a one dimensional array of
    pointers to mem_sections.  This two level layout scheme is able to achieve
    smaller memory requirements for SPARSEMEM with the tradeoff of an
    additional shift and load when fetching the memory section.  The current
    SPARSEMEM -mm implementation is a one dimensional array of mem_sections
    which is the default SPARSEMEM configuration.  The patch attempts isolates
    the implementation details of the physical layout of the sparsemem section
    array.
    
    ARCH_SPARSEMEM_EXTREME depends on 64BIT and is by default boolean false.
    
    I've boot tested under aim load ia64 configured for ARCH_SPARSEMEM_EXTREME.
     I've also boot tested a 4 way Opteron machine with !ARCH_SPARSEMEM_EXTREME
    and tested with aim.
    Signed-off-by: default avatarAndy Whitcroft <apw@shadowen.org>
    Signed-off-by: default avatarBob Picco <bob.picco@hp.com>
    Signed-off-by: default avatarDave Hansen <haveblue@us.ibm.com>
    Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
    802f192e
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