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    Subject[PATCH UPDATED x86/mm] x86-64, NUMA: Better explain numa_distance handling
    From 615e1632e55b6b8fb52da00c5e8540ef159f759b Mon Sep 17 00:00:00 2001
    From: Tejun Heo <tj@kernel.org>
    Date: Wed, 2 Mar 2011 11:32:47 +0100

    Handling of out-of-bounds distances and allocation failure can use
    better documentation. Add it.

    Signed-off-by: Tejun Heo <tj@kernel.org>
    Cc: Yinghai Lu <yinghai@kernel.org>
    ---
    Sorry, sent out the wrong version. This one is a bit more detailed
    and the version I put into the tree.

    Thanks.

    arch/x86/mm/numa_64.c | 11 ++++++++++-
    arch/x86/mm/numa_emulation.c | 6 +++++-
    2 files changed, 15 insertions(+), 2 deletions(-)

    diff --git a/arch/x86/mm/numa_64.c b/arch/x86/mm/numa_64.c
    index 541746f..74064e8 100644
    --- a/arch/x86/mm/numa_64.c
    +++ b/arch/x86/mm/numa_64.c
    @@ -392,11 +392,12 @@ void __init numa_reset_distance(void)
    {
    size_t size = numa_distance_cnt * numa_distance_cnt * sizeof(numa_distance[0]);

    + /* numa_distance could be 1LU marking allocation failure, test cnt */
    if (numa_distance_cnt)
    memblock_x86_free_range(__pa(numa_distance),
    __pa(numa_distance) + size);
    numa_distance_cnt = 0;
    - numa_distance = NULL;
    + numa_distance = NULL; /* enable table creation */
    }

    static int __init numa_alloc_distance(void)
    @@ -447,6 +448,14 @@ static int __init numa_alloc_distance(void)
    * Set the distance from node @from to @to to @distance. If distance table
    * doesn't exist, one which is large enough to accomodate all the currently
    * known nodes will be created.
    + *
    + * If such table cannot be allocated, a warning is printed and further
    + * calls are ignored until the distance table is reset with
    + * numa_reset_distance().
    + *
    + * If @from or @to is higher than the highest known node at the time of
    + * table creation or @distance doesn't make sense, the call is ignored.
    + * This is to allow simplification of specific NUMA config implementations.
    */
    void __init numa_set_distance(int from, int to, int distance)
    {
    diff --git a/arch/x86/mm/numa_emulation.c b/arch/x86/mm/numa_emulation.c
    index 0afa25d..aeecea9 100644
    --- a/arch/x86/mm/numa_emulation.c
    +++ b/arch/x86/mm/numa_emulation.c
    @@ -379,7 +379,11 @@ void __init numa_emulation(struct numa_meminfo *numa_meminfo, int numa_dist_cnt)
    if (emu_nid_to_phys[i] == NUMA_NO_NODE)
    emu_nid_to_phys[i] = 0;

    - /* transform distance table */
    + /*
    + * Transform distance table. numa_set_distance() ignores all
    + * out-of-bound distances. Just call it for every possible node
    + * combination.
    + */
    numa_reset_distance();
    for (i = 0; i < MAX_NUMNODES; i++) {
    for (j = 0; j < MAX_NUMNODES; j++) {
    --
    1.7.1


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