#define ITERATIONS (100000000)
+#define BEST_CASE_BOUND (1<<16)
+#define WORST_CASE_BOUND (BEST_CASE_BOUND + 1)
+
enum rand_type {
- rand_type_64
+ rand_type_64,
+ rand_type_bounded_best_case,
+ rand_type_bounded_worst_case
};
static const char *
switch (rand_type) {
case rand_type_64:
return "Full 64-bit [rte_rand()]";
+ case rand_type_bounded_best_case:
+ return "Bounded average best-case [rte_rand_max()]";
+ case rand_type_bounded_worst_case:
+ return "Bounded average worst-case [rte_rand_max()]";
default:
return NULL;
}
case rand_type_64:
sum += rte_rand();
break;
+ case rand_type_bounded_best_case:
+ sum += rte_rand_max(BEST_CASE_BOUND);
+ break;
+ case rand_type_bounded_worst_case:
+ sum += rte_rand_max(WORST_CASE_BOUND);
+ break;
}
}
printf("Pseudo-random number generation latencies:\n");
test_rand_perf_type(rand_type_64);
+ test_rand_perf_type(rand_type_bounded_best_case);
+ test_rand_perf_type(rand_type_bounded_worst_case);
return 0;
}
higher-quality pseudo-random numbers (including full 64 bit
support) and improved performance.
+ In addition, <rte_random.h> is extended with a new function
+ rte_rand_max() which supplies unbiased, bounded pseudo-random
+ numbers.
+
* **Updated the bnxt PMD.**
Updated the bnxt PMD. The major enhancements include:
#include <stdint.h>
+#include <rte_compat.h>
+
/**
* Seed the pseudo-random generator.
*
uint64_t
rte_rand(void);
+/**
+ * Generates a pseudo-random number with an upper bound.
+ *
+ * This function returns an uniformly distributed (unbiased) random
+ * number less than a user-specified maximum value.
+ *
+ * If called from lcore threads, this function is thread-safe.
+ *
+ * @param upper_bound
+ * The upper bound of the generated number.
+ * @return
+ * A pseudo-random value between 0 and (upper_bound-1).
+ */
+uint64_t __rte_experimental
+rte_rand_max(uint64_t upper_bound);
+
#ifdef __cplusplus
}
#endif
return __rte_rand_lfsr258(state);
}
+uint64_t __rte_experimental
+rte_rand_max(uint64_t upper_bound)
+{
+ struct rte_rand_state *state;
+ uint8_t ones;
+ uint8_t leading_zeros;
+ uint64_t mask = ~((uint64_t)0);
+ uint64_t res;
+
+ if (unlikely(upper_bound < 2))
+ return 0;
+
+ state = __rte_rand_get_state();
+
+ ones = __builtin_popcountll(upper_bound);
+
+ /* Handle power-of-2 upper_bound as a special case, since it
+ * has no bias issues.
+ */
+ if (unlikely(ones == 1))
+ return __rte_rand_lfsr258(state) & (upper_bound - 1);
+
+ /* The approach to avoiding bias is to create a mask that
+ * stretches beyond the request value range, and up to the
+ * next power-of-2. In case the masked generated random value
+ * is equal to or greater than the upper bound, just discard
+ * the value and generate a new one.
+ */
+
+ leading_zeros = __builtin_clzll(upper_bound);
+ mask >>= leading_zeros;
+
+ do {
+ res = __rte_rand_lfsr258(state) & mask;
+ } while (unlikely(res >= upper_bound));
+
+ return res;
+}
+
static uint64_t
__rte_random_initial_seed(void)
{
rte_mp_request_async;
rte_mp_sendmsg;
rte_option_register;
+ rte_rand_max;
rte_realloc_socket;
rte_service_lcore_attr_get;
rte_service_lcore_attr_reset_all;