• Aneesh Kumar K.V's avatar
    powerpc/papr_scm: Update the NUMA distance table for the target node · b277fc79
    Aneesh Kumar K.V authored
    Platform device helper routines won't update the NUMA distance table
    while creating a platform device, even if the device is present on a
    NUMA node that doesn't have memory or CPU. This is especially true for
    pmem devices. If the target node of the pmem device is not online, we
    find the nearest online node to the device and associate the pmem device
    with that online node. To find the nearest online node, we should have
    the numa distance table updated correctly. Update the distance
    information during the device probe.
    
    For a papr scm device on NUMA node 3 distance_lookup_table value for
    distance_ref_points_depth = 2 before and after fix is below:
    
    Before fix:
      node 3 distance depth 0  - 0
      node 3 distance depth 1  - 0
      node 4 distance depth 0  - 4
      node 4 distance depth 1  - 2
      node 5 distance depth 0  - 5
      node 5 distance depth 1  - 1
    
    After fix
      node 3 distance depth 0  - 3
      node 3 distance depth 1  - 1
      node 4 distance depth 0  - 4
      node 4 distance depth 1  - 2
      node 5 distance depth 0  - 5
      node 5 distance depth 1  - 1
    
    Without the fix, the nearest numa node to the pmem device (NUMA node 3)
    will be picked as 4. After the fix, we get the correct numa node which
    is 5.
    
    Fixes: da1115fd ("powerpc/nvdimm: Pick nearby online node if the device node is not online")
    Signed-off-by: default avatarAneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
    Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
    Link: https://msgid.link/20230404041433.1781804-1-aneesh.kumar@linux.ibm.com
    b277fc79
numa.c 36.2 KB