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>

diff --git a/lib/interval_tree_test.c b/lib/interval_tree_test.c
index 1093f0496d5e55678afdd7bd18545e9661952645..0fef6364a9580c817dcf331fbd36e91bf852efbe 100644 (file)
--- 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)