libfrog: print cdf of free space buckets

Print the cumulative distribution function of the free space buckets in
reverse order.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>

diff --git a/libfrog/histogram.c b/libfrog/histogram.c
index 7cee6b3500462b5cee57b9b987dd8e6ff6ed00db..59d46363c1da869d82a1efe1220ff690a1a18dcc 100644 (file)
--- a/libfrog/histogram.c
+++ b/libfrog/histogram.c
@@ -102,17 +102,81 @@ hist_free(
        memset(hs, 0, sizeof(struct histogram));
 }
 
+/*
+ * Compute the CDF of the histogram in decreasing order of value.
+ *
+ * For a free space histogram, callers can determine how much free space is not
+ * in the long tail of small extents, e.g. 98% of the free space extents are
+ * larger than 31 blocks.
+ */
+static struct histogram_cdf *
+hist_cdf(
+       const struct histogram  *hs)
+{
+       struct histogram_cdf    *cdf;
+       int                     i = hs->nr_buckets - 1;
+
+       ASSERT(hs->nr_buckets < INT_MAX);
+
+       cdf = malloc(sizeof(struct histogram_cdf));
+       if (!cdf)
+               return NULL;
+       cdf->histogram = hs;
+
+       if (hs->nr_buckets == 0) {
+               cdf->buckets = NULL;
+               return cdf;
+       }
+
+       cdf->buckets = calloc(hs->nr_buckets, sizeof(struct histbucket));
+       if (!cdf->buckets) {
+               free(cdf);
+               return NULL;
+       }
+
+       cdf->buckets[i].nr_obs = hs->buckets[i].nr_obs;
+       cdf->buckets[i].sum = hs->buckets[i].sum;
+       i--;
+
+       while (i >= 0) {
+               cdf->buckets[i].nr_obs = hs->buckets[i].nr_obs +
+                                       cdf->buckets[i + 1].nr_obs;
+
+               cdf->buckets[i].sum =    hs->buckets[i].sum +
+                                       cdf->buckets[i + 1].sum;
+               i--;
+       }
+
+       return cdf;
+}
+
+/* Free all data associated with a histogram cdf. */
+static void
+histcdf_free(
+       struct histogram_cdf    *cdf)
+{
+       free(cdf->buckets);
+       free(cdf);
+}
+
 /* Dump a histogram to stdout. */
 void
 hist_print(
        const struct histogram          *hs,
        const struct histogram_strings  *hstr)
 {
+       struct histogram_cdf            *cdf;
        unsigned int                    obs_w = strlen(hstr->observations);
        unsigned int                    sum_w = strlen(hstr->sum);
        unsigned int                    from_w = 7, to_w = 7;
        unsigned int                    i;
 
+       cdf = hist_cdf(hs);
+       if (!cdf) {
+               perror(_("histogram cdf"));
+               return;
+       }
+
        for (i = 0; i < hs->nr_buckets; i++) {
                char buf[256];
 
@@ -132,23 +196,27 @@ hist_print(
                sum_w = max(sum_w, strlen(buf));
        }
 
-       printf("%*s %*s %*s %*s %6s\n",
+       printf("%*s %*s %*s %*s %6s %6s %6s\n",
                        from_w, _("from"), to_w, _("to"),
                        obs_w, hstr->observations,
                        sum_w, hstr->sum,
-                       _("pct"));
+                       _("pct"), _("blkcdf"), _("extcdf"));
 
        for (i = 0; i < hs->nr_buckets; i++) {
                if (hs->buckets[i].nr_obs == 0)
                        continue;
 
-               printf("%*lld %*lld %*lld %*lld %6.2f\n",
+               printf("%*lld %*lld %*lld %*lld %6.2f %6.2f %6.2f\n",
                                from_w, hs->buckets[i].low,
                                to_w, hs->buckets[i].high,
                                obs_w, hs->buckets[i].nr_obs,
                                sum_w, hs->buckets[i].sum,
-                               hs->buckets[i].sum * 100.0 / hs->tot_sum);
+                               hs->buckets[i].sum * 100.0 / hs->tot_sum,
+                               cdf->buckets[i].sum * 100.0 / hs->tot_sum,
+                               cdf->buckets[i].nr_obs * 100.0 / hs->tot_obs);
        }
+
+       histcdf_free(cdf);
 }
 
 /* Summarize the contents of the histogram. */

diff --git a/libfrog/histogram.h b/libfrog/histogram.h
index 68afdeb29415ba4a5bb114598244c86d54f7d128..0c534f65dd9ad7c50b68ca16f97860f9481edf35 100644 (file)
--- a/libfrog/histogram.h
+++ b/libfrog/histogram.h
@@ -33,6 +33,14 @@ struct histogram {
        unsigned int            nr_buckets;
 };
 
+struct histogram_cdf {
+       /* histogram from which this cdf was computed */
+       const struct histogram  *histogram;
+
+       /* distribution information */
+       struct histbucket       *buckets;
+};
+
 int hist_add_bucket(struct histogram *hs, long long bucket_low);
 void hist_add(struct histogram *hs, long long value);
 void hist_init(struct histogram *hs);