DEBUG: lru: use a xorshift generator in the testing code
The standalone testing code used to rely on rand(), but switching to a
xorshift generator speeds up the test by 7% which is important to
accurately measure the real impact of the LRU code itself.
diff --git a/src/lru.c b/src/lru.c
index d58b188..f092588 100644
--- a/src/lru.c
+++ b/src/lru.c
@@ -262,6 +262,17 @@
return a;
}
+static inline unsigned int statistical_prng()
+{
+ static unsigned int statistical_prng_state = 0x12345678;
+ unsigned int x = statistical_prng_state;
+
+ x ^= x << 13;
+ x ^= x >> 17;
+ x ^= x << 5;
+ return statistical_prng_state = x;
+}
+
/* pass #of loops in argv[1] and set argv[2] to something to use the LRU */
int main(int argc, char **argv)
{
@@ -281,7 +292,7 @@
ret = 0;
for (loops = 0; loops < total; loops++) {
- ret += get_value(lru, rand() & 65535);
+ ret += get_value(lru, statistical_prng() & 65535);
}
/* just for accuracy control */
printf("ret=%llx, hits=%d, misses=%d (%d %% hits)\n", ret, total-misses, misses, (int)((float)(total-misses) * 100.0 / total));