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    SubjectRe: [PATCH 2.6.20-rc1 00/10] Kernel memory leak detector 0.13

    * Catalin Marinas <> wrote:

    > On 18/12/06, Ingo Molnar <> wrote:
    > >* Catalin Marinas <> wrote:
    > >> I could also use a simple allocator based on alloc_pages [...]
    > >> [...] It could be so simple that it would never need to free any
    > >> pages, just grow the size as required and reuse the freed memleak
    > >> objects from a list.
    > >
    > >sounds good to me. Please make it a per-CPU pool. We'll have to fix the
    > >locking too, to be per-CPU - memleak_lock is quite a scalability problem
    > >right now. (Add a memleak_object->cpu pointer so that freeing can be
    > >done on any other CPU as well.)
    > I did some simple statistics about allocations happening on one CPU
    > and freeing on a different one. On a 4-CPU ARM system (and without IRQ
    > balancing and without CONFIG_PREEMPT), these seem to happen in about
    > 8-10% of the cases. Do you expect higher figures on other
    > systems/configurations?
    > As I mentioned in a different e-mail, a way to remove the global hash
    > table is to create per-cpu hashes. The only problem is that in these
    > 8-10% of the cases, freeing would need to look up the other hashes.
    > This would become a problem with a high number of CPUs but I'm not
    > sure whether it would overtake the performance issues introduced by
    > cacheline ping-ponging in the single-hash case.

    i dont think it's worth doing that. So we should either do the current
    global lock & hash (bad for scalability), or a pure per-CPU design. The
    pure per-CPU design would have to embedd the CPU ID the object is
    attached to into the allocated object. If that is not feasible then only
    the global hash remains i think.

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