bh_accounting
static DEFINE_PER_CPU(struct bh_accounting, bh_accounting) = {0, 0};
if (__this_cpu_inc_return(bh_accounting.ratelimit) - 1 < 4096)
__this_cpu_write(bh_accounting.ratelimit, 0);
tot += per_cpu(bh_accounting, i).nr;
__this_cpu_inc(bh_accounting.nr);
__this_cpu_dec(bh_accounting.nr);
this_cpu_add(bh_accounting.nr, per_cpu(bh_accounting, cpu).nr);
per_cpu(bh_accounting, cpu).nr = 0;