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    SubjectRe: [PATCH] percpu_counter : add percpu_counter_add_fast()
    On Thu, 21 Oct 2010 18:10:13 -0500 (CDT) Christoph Lameter <cl@linux.com> wrote:

    > On Thu, 21 Oct 2010, Andrew Morton wrote:
    >
    > > That isn't actually what I was suggesting. I was suggesting the use of
    > > an inlined, this_cpu_add()-using percpu_counter_add() variant which
    > > still does the batched spilling into ->count. IOW, just speed up the
    > > current implementation along the lines of
    > >
    > > {
    > > val = this_cpu_add_return(*fbc->counters, amount);
    >
    > this_cpu_add_return() is not in the kernel but could be realized using a
    > variant offshoot of cmpxchg_local. I had something like that initially but
    > omitted it since there was no use case.

    this_cpu_add_return() isn't really needed in this application.

    {
    this_cpu_add(*fbc->counters, amount);
    if (unlikely(abs(this_cpu_read(*fbc->counters)) > fbc->batch))
    out_of_line_stuff();
    }

    will work just fine.


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