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    SubjectRe: [PATCH 2/9] Make cpuacct fields per cpu variables
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    On Wed, 2011-09-14 at 17:04 -0300, Glauber Costa wrote:
    > @@ -9258,11 +9253,17 @@ static int cpuacct_stats_show(struct cgroup *cgrp, struct cftype *cft,
    > struct cgroup_map_cb *cb)
    > {
    > struct cpuacct *ca = cgroup_ca(cgrp);
    > - int i;
    > + int i, cpu;
    > + u64 acc[CPUACCT_STAT_NSTATS] = { 0, };
    > +
    > + for_each_present_cpu(cpu) {
    > + u64 *vec = per_cpu_ptr(ca->cpustat, cpu);
    > + for (i = 0; i < CPUACCT_STAT_NSTATS; i++)
    > + acc[i] += vec[i];
    > + }
    >
    > for (i = 0; i < CPUACCT_STAT_NSTATS; i++) {
    > - s64 val = percpu_counter_read(&ca->cpustat[i]);
    > - val = cputime64_to_clock_t(val);
    > + s64 val = cputime64_to_clock_t(acc[i]);
    > cb->fill(cb, cpuacct_stat_desc[i], val);
    > }
    > return 0;

    The changelog doesn't mention this function is a lot more expensive now.

    Someone might have daft software polling this frequently.. at least its
    still fully preemptible so its not much of a problem, but it is
    something to be aware of.


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