Add outlier statistics for fast mixer cycle times

{

}

// helper function called by qsort()

static int compare_uint32_t(const void *pa, const void *pb)

{

    uint32_t a = *(const uint32_t *)pa;

    uint32_t b = *(const uint32_t *)pb;

    if (a < b) {

        return -1;

    } else if (a > b) {

        return 1;

    } else {

        return 0;

    }

}

void FastMixerDumpState::dump(int fd)

{

    if (mCommand == FastMixerState::INITIAL) {

    CentralTendencyStatistics kHz, loadMHz;

    uint32_t previousCpukHz = 0;

#endif

    // Assuming a normal distribution for cycle times, three standard deviations on either side of

    // the mean account for 99.73% of the population.  So if we take each tail to be 1/1000 of the

    // sample set, we get 99.8% combined, or close to three standard deviations.

    static const uint32_t kTailDenominator = 1000;

    uint32_t *tail = n >= kTailDenominator ? new uint32_t[n] : NULL;

    // loop over all the samples

    for (; n > 0; --n) {

    for (uint32_t j = 0; j < n; ++j) {

        size_t i = oldestClosed++ & (kSamplingN - 1);

        uint32_t wallNs = mMonotonicNs[i];

        if (tail != NULL) {

            tail[j] = wallNs;

        }

        wall.sample(wallNs);

        uint32_t sampleLoadNs = mLoadNs[i];

        loadNs.sample(sampleLoadNs);

                 "    mean=%.1f min=%.1f max=%.1f stddev=%.1f\n",

                 loadMHz.mean(), loadMHz.minimum(), loadMHz.maximum(), loadMHz.stddev());

#endif

    if (tail != NULL) {

        qsort(tail, n, sizeof(uint32_t), compare_uint32_t);

        // assume same number of tail samples on each side, left and right

        uint32_t count = n / kTailDenominator;

        CentralTendencyStatistics left, right;

        for (uint32_t i = 0; i < count; ++i) {

            left.sample(tail[i]);

            right.sample(tail[n - (i + 1)]);

        }

        fdprintf(fd, "Distribution of mix cycle times in ms for the tails (> ~3 stddev outliers):\n"

                     "  left tail: mean=%.2f min=%.2f max=%.2f stddev=%.2f\n"

                     "  right tail: mean=%.2f min=%.2f max=%.2f stddev=%.2f\n",

                     left.mean()*1e-6, left.minimum()*1e-6, left.maximum()*1e-6, left.stddev()*1e-6,

                     right.mean()*1e-6, right.minimum()*1e-6, right.maximum()*1e-6,

                     right.stddev()*1e-6);

        delete[] tail;

    }

#endif

    // The active track mask and track states are updated non-atomically.

    // So if we relied on isActive to decide whether to display,