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    Subject[PATCH] Fix fake numa on ppc
    Hello,

    Below is a patch to fix a couple of issues with fake numa node creation
    on ppc:

    1) Presently, fake nodes could be created such that real numa node
    boundaries are not respected. So a node could have lmbs that belong to
    different real nodes.

    2) The cpu association is broken. On a JS22 blade for example, which is
    a 2-node numa machine, I get the following:

    # cat /proc/cmdline
    root=/dev/sda6 numa=fake=2G,4G,,6G,8G,10G,12G,14G,16G
    # cat /sys/devices/system/node/node0/cpulist
    0-3
    # cat /sys/devices/system/node/node1/cpulist
    4-7
    # cat /sys/devices/system/node/node4/cpulist

    #

    So, though the cpus 4-7 should have been associated with node4, they
    still belong to node1. The patch works by recording a real numa node
    boundary and incrementing the fake node count. At the same time, a
    mapping is stored from the real numa node to the first fake node that
    gets created on it.

    Any suggestions on improving the patch are most welcome!

    Signed-off-by: Ankita Garg <ankita@in.ibm.com>

    Index: linux-2.6.31-rc5/arch/powerpc/mm/numa.c
    ===================================================================
    --- linux-2.6.31-rc5.orig/arch/powerpc/mm/numa.c
    +++ linux-2.6.31-rc5/arch/powerpc/mm/numa.c
    @@ -26,6 +26,11 @@
    #include <asm/smp.h>

    static int numa_enabled = 1;
    +static int fake_enabled = 1;
    +
    +/* The array maps a real numa node to the first fake node that gets
    +created on it */
    +int fake_numa_node_mapping[MAX_NUMNODES];

    static char *cmdline __initdata;

    @@ -49,14 +54,24 @@ static int __cpuinit fake_numa_create_ne
    unsigned long long mem;
    char *p = cmdline;
    static unsigned int fake_nid;
    + static unsigned int orig_nid = 0;
    static unsigned long long curr_boundary;

    /*
    * Modify node id, iff we started creating NUMA nodes
    * We want to continue from where we left of the last time
    */
    - if (fake_nid)
    + if (fake_nid) {
    + if (orig_nid != *nid) {
    + fake_nid++;
    + fake_numa_node_mapping[*nid] = fake_nid;
    + orig_nid = *nid;
    + *nid = fake_nid;
    + return 0;
    + }
    *nid = fake_nid;
    + }
    +
    /*
    * In case there are no more arguments to parse, the
    * node_id should be the same as the last fake node id
    @@ -440,7 +455,7 @@ static int of_drconf_to_nid_single(struc
    */
    static int __cpuinit numa_setup_cpu(unsigned long lcpu)
    {
    - int nid = 0;
    + int nid = 0, new_nid;
    struct device_node *cpu = of_get_cpu_node(lcpu, NULL);

    if (!cpu) {
    @@ -450,8 +465,15 @@ static int __cpuinit numa_setup_cpu(unsi

    nid = of_node_to_nid_single(cpu);

    + if (fake_enabled && nid) {
    + new_nid = fake_numa_node_mapping[nid];
    + if (new_nid > 0)
    + nid = new_nid;
    + }
    +
    if (nid < 0 || !node_online(nid))
    nid = any_online_node(NODE_MASK_ALL);
    +
    out:
    map_cpu_to_node(lcpu, nid);

    @@ -1005,8 +1027,11 @@ static int __init early_numa(char *p)
    numa_debug = 1;

    p = strstr(p, "fake=");
    - if (p)
    + if (p) {
    cmdline = p + strlen("fake=");
    + if (numa_enabled)
    + fake_enabled = 1;
    + }

    return 0;
    }
    --
    Regards,
    Ankita Garg (ankita@in.ibm.com)
    Linux Technology Center
    IBM India Systems & Technology Labs,
    Bangalore, India


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