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    SubjectRe: 2.2.18Pre Lan Performance Rocks!

    On Mon, 30 Oct 2000, Andi Kleen wrote:

    > One problem in Linux 2.2 is that kernel threads reload their VM on
    > context switch (that would include the nfsd thread), this should be
    > fixed in 2.4 with lazy mm. Hmm actually it should be only fixed for
    > true kernel threads that have been started with kernel_thread(), the
    > "pseudo kernel threads" like nfsd uses probably do not get that
    > optimization because they don't set their MM to init_mm.

    yes, but for this there is an explicit mechanizm to lazy-MM during lengthy
    system calls, an example is in buffer.c:

    user_mm = start_lazy_tlb();
    error = sync_old_buffers();
    end_lazy_tlb(user_mm);

    > > to get disproportiantely higher in Linux than NetWare 5.x and when it hits
    > > 60% of total clock cycles, Linux starts dropping off. NetWare 5.x is 1/8
    >
    > I think that can be explained by the copying.

    yes. Constant copying contaminates the L1/L2 caches and creates dirty
    cachelines all around the place. Fixed in 2.4 + TUX ;-)

    Ingo

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