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    SubjectRe: [SLUB 0/3] SLUB: The unqueued slab allocator V4
    On Thu, 8 Mar 2007, Christoph Lameter wrote:

    > Note that I am amazed that the kernbench even worked. On small machine

    How small? The machines I am testing on aren't "big" but they aren't
    misterable either.

    > I
    > seem to be getting into trouble with order 1 allocations.

    That in itself is pretty incredible. From what I see, allocations up to 3
    generally work unless they are atomic even with the vanilla kernel. That
    said, it could be because slab is holding onto the high order pages for
    itself.

    > SLAB seems to be
    > able to avoid the situation by keeping higher order pages on a freelist
    > and reduce the alloc/frees of higher order pages that the page allocator
    > has to deal with. Maybe we need per order queues in the page allocator?
    >

    I'm not sure what you mean by per-order queues. The buddy allocator
    already has per-order lists.

    > There must be something fundamentally wrong in the page allocator if the
    > SLAB queues fix this issue. I was able to fix the issue in V5 by forcing
    > SLUB to keep a mininum number of objects around regardless of the fit to
    > a page order page. Pass through is deadly since the crappy page allocator
    > cannot handle it.
    >
    > Higher order page allocation failures can be avoided by using kmalloc.
    > Yuck! Hopefully your patches fix that fundamental problem.
    >

    One way to find out for sure.

    --
    Mel Gorman
    Part-time Phd Student Linux Technology Center
    University of Limerick IBM Dublin Software Lab
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