• Mike Travis's avatar
    x86: fix cpu_to_node references · 98c9e27a
    Mike Travis authored
    In x86_64 and i386 architectures most arrays that are sized using
    NR_CPUS lay in local memory on node 0.  Not only will most (99%?) of the
    systems not use all the slots in these arrays, particularly when NR_CPUS
    is increased to accommodate future very high cpu count systems, but a
    number of cache lines are passed unnecessarily on the system bus when
    these arrays are referenced by cpus on other nodes.
    
    Typically, the values in these arrays are referenced by the cpu
    accessing it's own values, though when passing IPI interrupts, the cpu
    does access the data relevant to the targeted cpu/node.  Of course, if
    the referencing cpu is not on node 0, then the reference will still
    require cross node exchanges of cache lines.  A common use of this is
    for an interrupt service routine to pass the interrupt to other cpus
    local to that node.
    
    Ideally, all the elements in these arrays should be moved to the per_cpu
    data area.  In some cases (such as x86_cpu_to_apicid) the array is
    referenced before the per_cpu data areas are setup.  In this case, a
    static array is declared in the __initdata area and initialized by the
    booting cpu (BSP).  The values are then moved to the per_cpu area after
    it is initialized and the original static array is freed with the rest
    of the __initdata.
    
    This patch:
    
    Fix four instances where cpu_to_node is referenced by array instead of
    via the cpu_to_node macro.  This is preparation to moving it to the
    per_cpu data area.
    Signed-off-by: default avatarMike Travis <travis@sgi.com>
    Cc: Andi Kleen <ak@suse.de>
    Cc: Christoph Lameter <clameter@sgi.com>
    Cc: "Siddha, Suresh B" <suresh.b.siddha@intel.com>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
    Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
    98c9e27a
numa_64.c 16.5 KB