From: "Mattias Rönnblom" <mattias.ronnblom@ericsson.com>
To: <dev@dpdk.org>
Cc: "Mattias Rönnblom" <mattias.ronnblom@ericsson.com>
Subject: [dpdk-dev] [RFC 3/3] Introduce random generator functions with upper bound
Date: Mon, 8 Apr 2019 14:30:29 +0200 [thread overview]
Message-ID: <20190408123029.6701-3-mattias.ronnblom@ericsson.com> (raw)
Message-ID: <20190408123029.xVZ_INXtEL8KwSMgn94151V7tc77WliPkOj0ce2b9n4@z> (raw)
In-Reply-To: <20190408123029.6701-1-mattias.ronnblom@ericsson.com>
Add two functions rte_rand32_max() and rte_rand_max(), which generate
uniformly distributed pseudo-random number less than a user-specified
upper bound.
The commonly used pattern rte_rand() % SOME_VALUE, in addition to
being slow, also creates biased results if SOME_VALUE is not a power
of 2. This bias is very small for small SOME_VALUE, but increases
linearly with larger SOME_VALUE.
Signed-off-by: Mattias Rönnblom <mattias.ronnblom@ericsson.com>
---
lib/librte_eal/common/include/rte_random.h | 32 +++++++++++++++++
lib/librte_eal/common/rte_random.c | 40 ++++++++++++++++++++++
lib/librte_eal/rte_eal_version.map | 2 ++
3 files changed, 74 insertions(+)
diff --git a/lib/librte_eal/common/include/rte_random.h b/lib/librte_eal/common/include/rte_random.h
index a96fc7f96..b560b0a0d 100644
--- a/lib/librte_eal/common/include/rte_random.h
+++ b/lib/librte_eal/common/include/rte_random.h
@@ -45,6 +45,22 @@ rte_srand(uint64_t seedval);
uint32_t
rte_rand32(void);
+/**
+ * Generates an 32-bit pseudo-random number less than upper_bound.
+ *
+ * This function returns an uniformly distributed (unbiased) random
+ * number lower 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).
+ */
+uint32_t
+rte_rand32_max(uint32_t upper_bound);
+
/**
* Generates a 64-bit pseudo-random number.
*
@@ -56,6 +72,22 @@ rte_rand32(void);
uint64_t
rte_rand(void);
+/**
+ * Generates an 64-bit pseudo-random number less than upper_bound.
+ *
+ * This function returns an uniformly distributed (unbiased) random
+ * number lower 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_rand_max(uint64_t upper_bound);
+
#ifdef __cplusplus
}
#endif
diff --git a/lib/librte_eal/common/rte_random.c b/lib/librte_eal/common/rte_random.c
index c6dac2fc7..67d07d3ff 100644
--- a/lib/librte_eal/common/rte_random.c
+++ b/lib/librte_eal/common/rte_random.c
@@ -93,6 +93,26 @@ rte_rand32(void)
return __rte_rand32(state);
}
+uint32_t __rte_experimental
+rte_rand32_max(uint32_t upper_bound)
+{
+ uint32_t mask = ~((uint32_t)0);
+ uint8_t zeros;
+ uint32_t res;
+
+ if (upper_bound < 2)
+ return 0;
+
+ zeros = __builtin_clz(upper_bound);
+ mask >>= zeros;
+
+ do {
+ res = rte_rand32() & mask;
+ } while (unlikely(res >= upper_bound));
+
+ return res;
+}
+
uint64_t __rte_experimental
rte_rand(void)
{
@@ -108,6 +128,26 @@ rte_rand(void)
return low | (high << 32);
}
+uint64_t __rte_experimental
+rte_rand_max(uint64_t upper_bound)
+{
+ uint64_t mask = ~((uint64_t)0);
+ uint8_t zeros;
+ uint64_t res;
+
+ if (upper_bound < 2)
+ return 0;
+
+ zeros = __builtin_clzll(upper_bound);
+ mask >>= zeros;
+
+ do {
+ res = rte_rand() & mask;
+ } while (unlikely(res >= upper_bound));
+
+ return res;
+}
+
RTE_INIT(rte_rand_init)
{
rte_srand(rte_get_timer_cycles());
diff --git a/lib/librte_eal/rte_eal_version.map b/lib/librte_eal/rte_eal_version.map
index 027a22fe5..abdacb217 100644
--- a/lib/librte_eal/rte_eal_version.map
+++ b/lib/librte_eal/rte_eal_version.map
@@ -367,7 +367,9 @@ EXPERIMENTAL {
rte_mp_sendmsg;
rte_option_register;
rte_rand32;
+ rte_rand32_max;
rte_rand;
+ rte_rand_max;
rte_realloc_socket;
rte_service_lcore_attr_get;
rte_service_lcore_attr_reset_all;
--
2.17.1
next prev parent reply other threads:[~2019-04-08 12:30 UTC|newest]
Thread overview: 137+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-05 13:45 [dpdk-dev] [RFC] eal: make rte_rand() MT safe Mattias Rönnblom
2019-04-05 13:45 ` Mattias Rönnblom
2019-04-05 13:51 ` Mattias Rönnblom
2019-04-05 13:51 ` Mattias Rönnblom
2019-04-05 14:28 ` Bruce Richardson
2019-04-05 14:28 ` Bruce Richardson
2019-04-05 14:56 ` Mattias Rönnblom
2019-04-05 14:56 ` Mattias Rönnblom
2019-04-05 16:57 ` Stephen Hemminger
2019-04-05 16:57 ` Stephen Hemminger
2019-04-05 18:04 ` Mattias Rönnblom
2019-04-05 18:04 ` Mattias Rönnblom
2019-04-05 20:50 ` Stephen Hemminger
2019-04-05 20:50 ` Stephen Hemminger
2019-04-06 5:52 ` Mattias Rönnblom
2019-04-06 5:52 ` Mattias Rönnblom
2019-04-08 12:30 ` [dpdk-dev] [RFC 1/3] Replace lrand48-based rte_rand with LFSR generator Mattias Rönnblom
2019-04-08 12:30 ` Mattias Rönnblom
2019-04-08 12:30 ` [dpdk-dev] [RFC 2/3] Add 32-bit version of rte_rand Mattias Rönnblom
2019-04-08 12:30 ` Mattias Rönnblom
2019-04-08 12:30 ` Mattias Rönnblom [this message]
2019-04-08 12:30 ` [dpdk-dev] [RFC 3/3] Introduce random generator functions with upper bound Mattias Rönnblom
2019-04-08 12:47 ` [dpdk-dev] [RFC 1/3] Replace lrand48-based rte_rand with LFSR generator Mattias Rönnblom
2019-04-08 12:47 ` Mattias Rönnblom
2019-04-19 21:21 ` [dpdk-dev] [RFC v2 0/2] Pseudo-number generation improvements Mattias Rönnblom
2019-04-19 21:21 ` Mattias Rönnblom
2019-04-19 21:21 ` [dpdk-dev] [RFC v2 1/2] eal: replace libc-based random number generation with LFSR Mattias Rönnblom
2019-04-19 21:21 ` Mattias Rönnblom
2019-04-22 11:34 ` Neil Horman
2019-04-22 11:34 ` Neil Horman
2019-04-22 14:49 ` Stephen Hemminger
2019-04-22 14:49 ` Stephen Hemminger
2019-04-22 15:52 ` Mattias Rönnblom
2019-04-22 15:52 ` Mattias Rönnblom
2019-04-22 17:44 ` Mattias Rönnblom
2019-04-22 17:44 ` Mattias Rönnblom
2019-04-23 11:33 ` Neil Horman
2019-04-23 11:33 ` Neil Horman
2019-04-23 17:13 ` Mattias Rönnblom
2019-04-23 17:13 ` Mattias Rönnblom
2019-04-24 11:37 ` Neil Horman
2019-04-24 11:37 ` Neil Horman
2019-04-23 15:31 ` Stephen Hemminger
2019-04-23 15:31 ` Stephen Hemminger
2019-04-23 17:17 ` Mattias Rönnblom
2019-04-23 17:17 ` Mattias Rönnblom
2019-04-24 7:52 ` Mattias Rönnblom
2019-04-24 7:52 ` Mattias Rönnblom
2019-04-24 12:33 ` [dpdk-dev] [RFC v3 0/2] Pseudo-random number generation improvements Mattias Rönnblom
2019-04-24 12:33 ` Mattias Rönnblom
2019-04-24 12:33 ` [dpdk-dev] [RFC v3 1/2] eal: replace libc-based random number generation with LFSR Mattias Rönnblom
2019-04-24 12:33 ` Mattias Rönnblom
2019-05-08 20:12 ` Stephen Hemminger
2019-05-08 20:12 ` Stephen Hemminger
2019-05-08 20:30 ` Mattias Rönnblom
2019-05-08 20:30 ` Mattias Rönnblom
2019-05-09 1:10 ` Stephen Hemminger
2019-05-09 1:10 ` Stephen Hemminger
2019-05-14 9:20 ` [dpdk-dev] [PATCH 0/6] Pseudo-random number generation improvements Mattias Rönnblom
2019-05-14 9:20 ` Mattias Rönnblom
2019-05-14 9:20 ` [dpdk-dev] [PATCH 1/6] eal: replace libc-based random number generation with LFSR Mattias Rönnblom
2019-05-14 9:20 ` Mattias Rönnblom
2019-05-14 9:32 ` Mattias Rönnblom
2019-05-14 9:32 ` Mattias Rönnblom
2019-05-14 14:16 ` Neil Horman
2019-05-14 14:16 ` Neil Horman
2019-05-14 14:53 ` Mattias Rönnblom
2019-05-14 14:53 ` Mattias Rönnblom
2019-05-17 19:27 ` Neil Horman
2019-05-17 20:57 ` Bruce Richardson
2019-05-17 21:10 ` Mattias Rönnblom
2019-05-19 18:32 ` Neil Horman
2019-05-14 15:27 ` Stephen Hemminger
2019-05-14 15:27 ` Stephen Hemminger
2019-05-14 9:20 ` [dpdk-dev] [PATCH 2/6] eal: add pseudo-random number generation performance test Mattias Rönnblom
2019-05-14 9:20 ` Mattias Rönnblom
2019-05-14 9:20 ` [dpdk-dev] [PATCH 3/6] eal: improve entropy for initial PRNG seed Mattias Rönnblom
2019-05-14 9:20 ` Mattias Rönnblom
2019-05-14 9:36 ` Mattias Rönnblom
2019-05-14 9:36 ` Mattias Rönnblom
2019-05-14 9:39 ` Bruce Richardson
2019-05-14 9:39 ` Bruce Richardson
2019-05-14 11:58 ` Mattias Rönnblom
2019-05-14 11:58 ` Mattias Rönnblom
2019-05-14 9:37 ` Bruce Richardson
2019-05-14 9:37 ` Bruce Richardson
2019-05-14 9:20 ` [dpdk-dev] [PATCH 4/6] eal: introduce random generator function with upper bound Mattias Rönnblom
2019-05-14 9:20 ` Mattias Rönnblom
2019-05-14 9:20 ` [dpdk-dev] [PATCH 5/6] eal: add bounded PRNG performance tests Mattias Rönnblom
2019-05-14 9:20 ` Mattias Rönnblom
2019-05-14 9:20 ` [dpdk-dev] [PATCH 6/6] eal: add pseudo-random number generation to MAINTAINERS Mattias Rönnblom
2019-05-14 9:20 ` Mattias Rönnblom
2019-05-16 17:55 ` [dpdk-dev] [PATCH v2 0/6] Pseudo-random number generation improvements Mattias Rönnblom
2019-05-16 17:55 ` [dpdk-dev] [PATCH v2 1/6] eal: replace libc-based random number generation with LFSR Mattias Rönnblom
2019-05-16 17:55 ` [dpdk-dev] [PATCH v2 2/6] eal: add pseudo-random number generation performance test Mattias Rönnblom
2019-05-16 17:55 ` [dpdk-dev] [PATCH v2 3/6] eal: improve entropy for initial PRNG seed Mattias Rönnblom
2019-05-16 17:55 ` [dpdk-dev] [PATCH v2 4/6] eal: introduce random generator function with upper bound Mattias Rönnblom
2019-05-16 17:55 ` [dpdk-dev] [PATCH v2 5/6] eal: add bounded PRNG performance tests Mattias Rönnblom
2019-05-16 17:55 ` [dpdk-dev] [PATCH v2 6/6] eal: add PRNG to MAINTAINERS and release notes Mattias Rönnblom
2019-05-16 20:35 ` [dpdk-dev] [PATCH v2 0/6] Pseudo-random number generation improvements Bruce Richardson
2019-06-05 10:43 ` [dpdk-dev] [PATCH v3 " Mattias Rönnblom
2019-06-05 10:43 ` [dpdk-dev] [PATCH v3 1/6] eal: replace libc-based random number generation with LFSR Mattias Rönnblom
2019-06-05 10:43 ` [dpdk-dev] [PATCH v3 2/6] eal: add pseudo-random number generation performance test Mattias Rönnblom
2019-06-27 21:23 ` Thomas Monjalon
2019-06-28 8:20 ` Mattias Rönnblom
2019-06-05 10:43 ` [dpdk-dev] [PATCH v3 3/6] eal: improve entropy for initial PRNG seed Mattias Rönnblom
2019-06-05 10:43 ` [dpdk-dev] [PATCH v3 4/6] eal: introduce random generator function with upper bound Mattias Rönnblom
2019-06-05 10:43 ` [dpdk-dev] [PATCH v3 5/6] eal: add bounded PRNG performance tests Mattias Rönnblom
2019-06-05 10:44 ` [dpdk-dev] [PATCH v3 6/6] eal: add PRNG to MAINTAINERS and release notes Mattias Rönnblom
2019-06-27 21:27 ` Thomas Monjalon
2019-06-28 8:17 ` Mattias Rönnblom
2019-06-15 12:23 ` [dpdk-dev] [PATCH v3 0/6] Pseudo-random number generation improvements Mattias Rönnblom
2019-06-28 9:01 ` [dpdk-dev] [PATCH v4 0/5] " Mattias Rönnblom
2019-06-28 9:01 ` [dpdk-dev] [PATCH v4 1/5] eal: replace libc-based random number generation with LFSR Mattias Rönnblom
2019-06-28 9:01 ` [dpdk-dev] [PATCH v4 2/5] eal: add pseudo-random number generation performance test Mattias Rönnblom
2019-06-28 9:01 ` [dpdk-dev] [PATCH v4 3/5] eal: improve entropy for initial PRNG seed Mattias Rönnblom
2019-06-28 19:01 ` Ferruh Yigit
2019-06-28 20:58 ` Mattias Rönnblom
2019-06-28 21:08 ` [dpdk-dev] [PATCH] eal: use 32-bit RDSEED to allow 32-bit x86 usage Mattias Rönnblom
2019-06-29 12:54 ` Thomas Monjalon
2019-06-28 9:01 ` [dpdk-dev] [PATCH v4 4/5] eal: introduce random generator function with upper bound Mattias Rönnblom
2019-06-28 9:01 ` [dpdk-dev] [PATCH v4 5/5] eal: add bounded PRNG performance tests Mattias Rönnblom
2019-06-28 13:24 ` [dpdk-dev] [PATCH v4 0/5] Pseudo-random number generation improvements Thomas Monjalon
2019-04-24 12:33 ` [dpdk-dev] [RFC v3 2/2] eal: introduce random generator function with upper bound Mattias Rönnblom
2019-04-24 12:33 ` Mattias Rönnblom
2019-04-19 21:21 ` [dpdk-dev] [RFC v2 " Mattias Rönnblom
2019-04-19 21:21 ` Mattias Rönnblom
2019-04-20 21:08 ` Wiles, Keith
2019-04-20 21:08 ` Wiles, Keith
2019-04-21 19:05 ` Mattias Rönnblom
2019-04-21 19:05 ` Mattias Rönnblom
2019-04-22 4:33 ` Wiles, Keith
2019-04-22 4:33 ` Wiles, Keith
2019-04-22 7:07 ` Mattias Rönnblom
2019-04-22 7:07 ` Mattias Rönnblom
2019-04-22 13:19 ` Wiles, Keith
2019-04-22 13:19 ` Wiles, Keith
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