• Tejun Heo's avatar
    percpu: introduce pcpu_alloc_info and pcpu_group_info · fd1e8a1f
    Tejun Heo authored
    Till now, non-linear cpu->unit map was expressed using an integer
    array which maps each cpu to a unit and used only by lpage allocator.
    Although how many units have been placed in a single contiguos area
    (group) is known while building unit_map, the information is lost when
    the result is recorded into the unit_map array.  For lpage allocator,
    as all allocations are done by lpages and whether two adjacent lpages
    are in the same group or not is irrelevant, this didn't cause any
    problem.  Non-linear cpu->unit mapping will be used for sparse
    embedding and this grouping information is necessary for that.
    
    This patch introduces pcpu_alloc_info which contains all the
    information necessary for initializing percpu allocator.
    pcpu_alloc_info contains array of pcpu_group_info which describes how
    units are grouped and mapped to cpus.  pcpu_group_info also has
    base_offset field to specify its offset from the chunk's base address.
    pcpu_build_alloc_info() initializes this field as if all groups are
    allocated back-to-back as is currently done but this will be used to
    sparsely place groups.
    
    pcpu_alloc_info is a rather complex data structure which contains a
    flexible array which in turn points to nested cpu_map arrays.
    
    * pcpu_alloc_alloc_info() and pcpu_free_alloc_info() are provided to
      help dealing with pcpu_alloc_info.
    
    * pcpu_lpage_build_unit_map() is updated to build pcpu_alloc_info,
      generalized and renamed to pcpu_build_alloc_info().
      @cpu_distance_fn may be NULL indicating that all cpus are of
      LOCAL_DISTANCE.
    
    * pcpul_lpage_dump_cfg() is updated to process pcpu_alloc_info,
      generalized and renamed to pcpu_dump_alloc_info().  It now also
      prints which group each alloc unit belongs to.
    
    * pcpu_setup_first_chunk() now takes pcpu_alloc_info instead of the
      separate parameters.  All first chunk allocators are updated to use
      pcpu_build_alloc_info() to build alloc_info and call
      pcpu_setup_first_chunk() with it.  This has the side effect of
      packing units for sparse possible cpus.  ie. if cpus 0, 2 and 4 are
      possible, they'll be assigned unit 0, 1 and 2 instead of 0, 2 and 4.
    
    * x86 setup_pcpu_lpage() is updated to deal with alloc_info.
    
    * sparc64 setup_per_cpu_areas() is updated to build alloc_info.
    
    Although the changes made by this patch are pretty pervasive, it
    doesn't cause any behavior difference other than packing of sparse
    cpus.  It mostly changes how information is passed among
    initialization functions and makes room for more flexibility.
    Signed-off-by: default avatarTejun Heo <tj@kernel.org>
    Cc: Ingo Molnar <mingo@elte.hu>
    Cc: David Miller <davem@davemloft.net>
    fd1e8a1f
smp_64.c 36 KB