• Christoph Lameter's avatar
    slub: Fallback to kmalloc_large for failing higher order allocs · 71c7a06f
    Christoph Lameter authored
    Slub already has two ways of allocating an object. One is via its own
    logic and the other is via the call to kmalloc_large to hand off object
    allocation to the page allocator. kmalloc_large is typically used
    for objects >= PAGE_SIZE.
    We can use that handoff to avoid failing if a higher order kmalloc slab
    allocation cannot be satisfied by the page allocator. If we reach the
    out of memory path then simply try a kmalloc_large(). kfree() can
    already handle the case of an object that was allocated via the page
    allocator and so this will work just fine (apart from object
    For any kmalloc slab that already requires higher order allocs (which
    makes it impossible to use the page allocator fastpath!)
    we just use PAGE_ALLOC_COSTLY_ORDER to get the largest number of
    objects in one go from the page allocator slowpath.
    On a 4k platform this patch will lead to the following use of higher
    order pages for the following kmalloc slabs:
    8 ... 1024	order 0
    2048 .. 4096	order 3 (4k slab only after the next patch)
    We may waste some space if fallback occurs on a 2k slab but we
    are always able to fallback to an order 0 alloc.
    Reviewed-by: default avatarPekka Enberg <penberg@cs.helsinki.fi>
    Signed-off-by: default avatarChristoph Lameter <clameter@sgi.com>