• Nishanth Aravamudan's avatar
    hugetlb: fix hugepage allocation with memoryless nodes · 63b4613c
    Nishanth Aravamudan authored
    Anton found a problem with the hugetlb pool allocation when some nodes have
    no memory (http://marc.info/?l=linux-mm&m=118133042025995&w=2
    
    ).  Lee worked
    on versions that tried to fix it, but none were accepted.  Christoph has
    created a set of patches which allow for GFP_THISNODE allocations to fail
    if the node has no memory.
    
    Currently, alloc_fresh_huge_page() returns NULL when it is not able to
    allocate a huge page on the current node, as specified by its custom
    interleave variable.  The callers of this function, though, assume that a
    failure in alloc_fresh_huge_page() indicates no hugepages can be allocated
    on the system period.  This might not be the case, for instance, if we have
    an uneven NUMA system, and we happen to try to allocate a hugepage on a
    node with less memory and fail, while there is still plenty of free memory
    on the other nodes.
    
    To correct this, make alloc_fresh_huge_page() search through all online
    nodes before deciding no hugepages can be allocated.  Add a helper function
    for actually allocating the hugepage.  Use a new global nid iterator to
    control which nid to allocate on.
    
    Note: we expect particular semantics for __GFP_THISNODE, which are now
    enforced even for memoryless nodes.  That is, there is should be no
    fallback to other nodes.  Therefore, we rely on the nid passed into
    alloc_pages_node() to be the nid the page comes from.  If this is
    incorrect, accounting will break.
    
    Tested on x86 !NUMA, x86 NUMA, x86_64 NUMA and ppc64 NUMA (with 2
    memoryless nodes).
    
    Before on the ppc64 box:
    Trying to clear the hugetlb pool
    Done.       0 free
    Trying to resize the pool to 100
    Node 0 HugePages_Free:     25
    Node 1 HugePages_Free:     75
    Node 2 HugePages_Free:      0
    Node 3 HugePages_Free:      0
    Done. Initially     100 free
    Trying to resize the pool to 200
    Node 0 HugePages_Free:     50
    Node 1 HugePages_Free:    150
    Node 2 HugePages_Free:      0
    Node 3 HugePages_Free:      0
    Done.     200 free
    
    After:
    Trying to clear the hugetlb pool
    Done.       0 free
    Trying to resize the pool to 100
    Node 0 HugePages_Free:     50
    Node 1 HugePages_Free:     50
    Node 2 HugePages_Free:      0
    Node 3 HugePages_Free:      0
    Done. Initially     100 free
    Trying to resize the pool to 200
    Node 0 HugePages_Free:    100
    Node 1 HugePages_Free:    100
    Node 2 HugePages_Free:      0
    Node 3 HugePages_Free:      0
    Done.     200 free
    
    Signed-off-by: default avatarNishanth Aravamudan <nacc@us.ibm.com>
    Acked-by: default avatarChristoph Lameter <clameter@sgi.com>
    Cc: Adam Litke <agl@us.ibm.com>
    Cc: David Gibson <hermes@gibson.dropbear.id.au>
    Cc: Badari Pulavarty <pbadari@us.ibm.com>
    Cc: Ken Chen <kenchen@google.com>
    Cc: William Lee Irwin III <wli@holomorphy.com>
    Cc: Lee Schermerhorn <lee.schermerhorn@hp.com>
    Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    63b4613c