lib/interval_tree_test.c: allow users to limit scope of endpoint

Add a 'max_endpoint' parameter such that users may easily limit the size
of the intervals that are randomly generated.

Link: http://lkml.kernel.org/r/20170518174936.20265-4-dave@stgolabs.net
Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 13 insertions, 10 deletions

diff --git a/lib/interval_tree_test.c b/lib/interval_tree_test.c
index 1093f0496d5e..0fef6364a958 100644
--- a/lib/interval_tree_test.c
+++ b/lib/interval_tree_test.c
@@ -16,6 +16,7 @@ __param(int, perf_loops, 100000, "Number of iterations modifying the tree");
 __param(int, nsearches, 100, "Number of searches to the interval tree");
 __param(int, search_loops, 10000, "Number of iterations searching the tree");
 
+__param(uint, max_endpoint, ~0, "Largest value for the interval's endpoint");
 
 static struct rb_root root = RB_ROOT;
 static struct interval_tree_node *nodes = NULL;
@@ -40,18 +41,20 @@ static void init(void)
         int i;
 
         for (i = 0; i < nnodes; i++) {
-                u32 a = prandom_u32_state(&rnd);
-                u32 b = prandom_u32_state(&rnd);
-                if (a <= b) {
-                        nodes[i].start = a;
-                        nodes[i].last = b;
-                } else {
-                        nodes[i].start = b;
-                        nodes[i].last = a;
-                }
+                u32 b = (prandom_u32_state(&rnd) >> 4) % max_endpoint;
+                u32 a = (prandom_u32_state(&rnd) >> 4) % b;
+
+                nodes[i].start = a;
+                nodes[i].last = b;
         }
+
+        /*
+         * Limit the search scope to what the user defined.
+         * Otherwise we are merely measuring empty walks,
+         * which is pointless.
+         */
         for (i = 0; i < nsearches; i++)
-                queries[i] = prandom_u32_state(&rnd);
+                queries[i] = (prandom_u32_state(&rnd) >> 4) % max_endpoint;
 }
 
 static int interval_tree_test_init(void)