• Christoph Lameter's avatar
    Move remote node draining out of slab allocators · 4037d452
    Christoph Lameter authored
    Currently the slab allocators contain callbacks into the page allocator to
    perform the draining of pagesets on remote nodes.  This requires SLUB to have
    a whole subsystem in order to be compatible with SLAB.  Moving node draining
    out of the slab allocators avoids a section of code in SLUB.
    Move the node draining so that is is done when the vm statistics are updated.
    At that point we are already touching all the cachelines with the pagesets of
    a processor.
    Add a expire counter there.  If we have to update per zone or global vm
    statistics then assume that the pageset will require subsequent draining.
    The expire counter will be decremented on each vm stats update pass until it
    reaches zero.  Then we will drain one batch from the pageset.  The draining
    will cause vm counter updates which will then cause another expiration until
    the pcp is empty.  So we will drain a batch every 3 seconds.
    Note that remote node draining is a somewhat esoteric feature that is required
    on large NUMA systems because otherwise significant portions of system memory
    can become trapped in pcp queues.  The number of pcp is determined by the
    number of processors and nodes in a system.  A system with 4 processors and 2
    nodes has 8 pcps which is okay.  But a system with 1024 processors and 512
    nodes has 512k pcps with a high potential for large amount of memory being
    caught in them.
    Signed-off-by: default avatarChristoph Lameter <clameter@sgi.com>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>