[dpdk-dev] [PATCH v4 1/5] eal: replace libc-based random number generation with LFSR
Mattias Rönnblom
mattias.ronnblom at ericsson.com
Fri Jun 28 11:01:20 CEST 2019
This commit replaces rte_rand()'s use of lrand48() with a DPDK-native
combined Linear Feedback Shift Register (LFSR) (also known as
Tausworthe) pseudo-random number generator.
This generator is faster and produces better-quality random numbers
than the linear congruential generator (LCG) of lib's lrand48(). The
implementation, as opposed to lrand48(), is multi-thread safe in
regards to concurrent rte_rand() calls from different lcore threads.
A LCG is still used, but only to seed the five per-lcore LFSR
sequences.
In addition, this patch also addresses the issue of the legacy
implementation only producing 62 bits of pseudo randomness, while the
API requires all 64 bits to be random.
This pseudo-random number generator is not cryptographically secure -
just like lrand48().
Bugzilla ID: 114
Bugzilla ID: 276
Signed-off-by: Mattias Rönnblom <mattias.ronnblom at ericsson.com>
Acked-by: Bruce Richardson <bruce.richardson at intel.com>
---
MAINTAINERS | 5 +
doc/guides/rel_notes/release_19_08.rst | 9 ++
lib/librte_eal/common/include/rte_random.h | 29 ++---
lib/librte_eal/common/meson.build | 1 +
lib/librte_eal/common/rte_random.c | 139 +++++++++++++++++++++
lib/librte_eal/freebsd/eal/Makefile | 1 +
lib/librte_eal/freebsd/eal/eal.c | 2 -
lib/librte_eal/linux/eal/Makefile | 1 +
lib/librte_eal/linux/eal/eal.c | 2 -
lib/librte_eal/rte_eal_version.map | 2 +
10 files changed, 169 insertions(+), 22 deletions(-)
create mode 100644 lib/librte_eal/common/rte_random.c
diff --git a/MAINTAINERS b/MAINTAINERS
index 0c3b48920..75775129d 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -227,6 +227,11 @@ M: Joyce Kong <joyce.kong at arm.com>
F: lib/librte_eal/common/include/generic/rte_ticketlock.h
F: app/test/test_ticketlock.c
+Pseudo-random Number Generation
+M: Mattias Rönnblom <mattias.ronnblom at ericsson.com>
+F: lib/librte_eal/common/include/rte_random.h
+F: lib/librte_eal/common/rte_random.c
+
ARM v7
M: Jan Viktorin <viktorin at rehivetech.com>
M: Gavin Hu <gavin.hu at arm.com>
diff --git a/doc/guides/rel_notes/release_19_08.rst b/doc/guides/rel_notes/release_19_08.rst
index 3da266705..7080d1f47 100644
--- a/doc/guides/rel_notes/release_19_08.rst
+++ b/doc/guides/rel_notes/release_19_08.rst
@@ -99,6 +99,15 @@ New Features
Updated ``librte_telemetry`` to fetch the global metrics from the
``librte_metrics`` library.
+* **Updated the EAL Pseudo-random Number Generator.**
+
+ The lrand48()-based rte_rand() function is replaced with a
+ DPDK-native combined Linear Feedback Shift Register (LFSR)
+ pseudo-random number generator (PRNG).
+
+ This new PRNG implementation is multi-thread safe, provides
+ higher-quality pseudo-random numbers (including full 64 bit
+ support) and improved performance.
Removed Items
-------------
diff --git a/lib/librte_eal/common/include/rte_random.h b/lib/librte_eal/common/include/rte_random.h
index b2ca1c209..66dfe8ae7 100644
--- a/lib/librte_eal/common/include/rte_random.h
+++ b/lib/librte_eal/common/include/rte_random.h
@@ -16,7 +16,6 @@ extern "C" {
#endif
#include <stdint.h>
-#include <stdlib.h>
/**
* Seed the pseudo-random generator.
@@ -25,34 +24,28 @@ extern "C" {
* value. It may need to be re-seeded by the user with a real random
* value.
*
+ * This function is not multi-thread safe in regards to other
+ * rte_srand() calls, nor is it in relation to concurrent rte_rand()
+ * calls.
+ *
* @param seedval
* The value of the seed.
*/
-static inline void
-rte_srand(uint64_t seedval)
-{
- srand48((long)seedval);
-}
+void
+rte_srand(uint64_t seedval);
/**
* Get a pseudo-random value.
*
- * This function generates pseudo-random numbers using the linear
- * congruential algorithm and 48-bit integer arithmetic, called twice
- * to generate a 64-bit value.
+ * The generator is not cryptographically secure.
+ *
+ * If called from lcore threads, this function is thread-safe.
*
* @return
* A pseudo-random value between 0 and (1<<64)-1.
*/
-static inline uint64_t
-rte_rand(void)
-{
- uint64_t val;
- val = (uint64_t)lrand48();
- val <<= 32;
- val += (uint64_t)lrand48();
- return val;
-}
+uint64_t
+rte_rand(void);
#ifdef __cplusplus
}
diff --git a/lib/librte_eal/common/meson.build b/lib/librte_eal/common/meson.build
index 0670e4102..bafd23207 100644
--- a/lib/librte_eal/common/meson.build
+++ b/lib/librte_eal/common/meson.build
@@ -35,6 +35,7 @@ common_sources = files(
'rte_keepalive.c',
'rte_malloc.c',
'rte_option.c',
+ 'rte_random.c',
'rte_reciprocal.c',
'rte_service.c'
)
diff --git a/lib/librte_eal/common/rte_random.c b/lib/librte_eal/common/rte_random.c
new file mode 100644
index 000000000..4d3cf5226
--- /dev/null
+++ b/lib/librte_eal/common/rte_random.c
@@ -0,0 +1,139 @@
+/* SPDX-License-Identifier: BSD-3-Clause
+ * Copyright(c) 2019 Ericsson AB
+ */
+
+#include <stdlib.h>
+
+#include <rte_branch_prediction.h>
+#include <rte_cycles.h>
+#include <rte_eal.h>
+#include <rte_lcore.h>
+#include <rte_memory.h>
+#include <rte_random.h>
+
+struct rte_rand_state {
+ uint64_t z1;
+ uint64_t z2;
+ uint64_t z3;
+ uint64_t z4;
+ uint64_t z5;
+} __rte_cache_aligned;
+
+static struct rte_rand_state rand_states[RTE_MAX_LCORE];
+
+static uint32_t
+__rte_rand_lcg32(uint32_t *seed)
+{
+ *seed = 1103515245U * *seed + 12345U;
+
+ return *seed;
+}
+
+static uint64_t
+__rte_rand_lcg64(uint32_t *seed)
+{
+ uint64_t low;
+ uint64_t high;
+
+ /* A 64-bit LCG would have been much cleaner, but good
+ * multiplier/increments for such seem hard to come by.
+ */
+
+ low = __rte_rand_lcg32(seed);
+ high = __rte_rand_lcg32(seed);
+
+ return low | (high << 32);
+}
+
+static uint64_t
+__rte_rand_lfsr258_gen_seed(uint32_t *seed, uint64_t min_value)
+{
+ uint64_t res;
+
+ res = __rte_rand_lcg64(seed);
+
+ if (res < min_value)
+ res += min_value;
+
+ return res;
+}
+
+static void
+__rte_srand_lfsr258(uint64_t seed, struct rte_rand_state *state)
+{
+ uint32_t lcg_seed;
+
+ lcg_seed = (uint32_t)(seed ^ (seed >> 32));
+
+ state->z1 = __rte_rand_lfsr258_gen_seed(&lcg_seed, 2UL);
+ state->z2 = __rte_rand_lfsr258_gen_seed(&lcg_seed, 512UL);
+ state->z3 = __rte_rand_lfsr258_gen_seed(&lcg_seed, 4096UL);
+ state->z4 = __rte_rand_lfsr258_gen_seed(&lcg_seed, 131072UL);
+ state->z5 = __rte_rand_lfsr258_gen_seed(&lcg_seed, 8388608UL);
+}
+
+void
+rte_srand(uint64_t seed)
+{
+ unsigned int lcore_id;
+
+ /* add lcore_id to seed to avoid having the same sequence */
+ for (lcore_id = 0; lcore_id < RTE_MAX_LCORE; lcore_id++)
+ __rte_srand_lfsr258(seed + lcore_id, &rand_states[lcore_id]);
+}
+
+static __rte_always_inline uint64_t
+__rte_rand_lfsr258_comp(uint64_t z, uint64_t a, uint64_t b, uint64_t c,
+ uint64_t d)
+{
+ return ((z & c) << d) ^ (((z << a) ^ z) >> b);
+}
+
+/* Based on L’Ecuyer, P.: Tables of maximally equidistributed combined
+ * LFSR generators.
+ */
+
+static __rte_always_inline uint64_t
+__rte_rand_lfsr258(struct rte_rand_state *state)
+{
+ state->z1 = __rte_rand_lfsr258_comp(state->z1, 1UL, 53UL,
+ 18446744073709551614UL, 10UL);
+ state->z2 = __rte_rand_lfsr258_comp(state->z2, 24UL, 50UL,
+ 18446744073709551104UL, 5UL);
+ state->z3 = __rte_rand_lfsr258_comp(state->z3, 3UL, 23UL,
+ 18446744073709547520UL, 29UL);
+ state->z4 = __rte_rand_lfsr258_comp(state->z4, 5UL, 24UL,
+ 18446744073709420544UL, 23UL);
+ state->z5 = __rte_rand_lfsr258_comp(state->z5, 3UL, 33UL,
+ 18446744073701163008UL, 8UL);
+
+ return state->z1 ^ state->z2 ^ state->z3 ^ state->z4 ^ state->z5;
+}
+
+static __rte_always_inline
+struct rte_rand_state *__rte_rand_get_state(void)
+{
+ unsigned int lcore_id;
+
+ lcore_id = rte_lcore_id();
+
+ if (unlikely(lcore_id == LCORE_ID_ANY))
+ lcore_id = rte_get_master_lcore();
+
+ return &rand_states[lcore_id];
+}
+
+uint64_t
+rte_rand(void)
+{
+ struct rte_rand_state *state;
+
+ state = __rte_rand_get_state();
+
+ return __rte_rand_lfsr258(state);
+}
+
+RTE_INIT(rte_rand_init)
+{
+ rte_srand(rte_get_timer_cycles());
+}
diff --git a/lib/librte_eal/freebsd/eal/Makefile b/lib/librte_eal/freebsd/eal/Makefile
index 19854ee2c..ca616c480 100644
--- a/lib/librte_eal/freebsd/eal/Makefile
+++ b/lib/librte_eal/freebsd/eal/Makefile
@@ -69,6 +69,7 @@ SRCS-$(CONFIG_RTE_EXEC_ENV_FREEBSD) += malloc_mp.c
SRCS-$(CONFIG_RTE_EXEC_ENV_FREEBSD) += rte_keepalive.c
SRCS-$(CONFIG_RTE_EXEC_ENV_FREEBSD) += rte_option.c
SRCS-$(CONFIG_RTE_EXEC_ENV_FREEBSD) += rte_service.c
+SRCS-$(CONFIG_RTE_EXEC_ENV_FREEBSD) += rte_random.c
SRCS-$(CONFIG_RTE_EXEC_ENV_FREEBSD) += rte_reciprocal.c
# from arch dir
diff --git a/lib/librte_eal/freebsd/eal/eal.c b/lib/librte_eal/freebsd/eal/eal.c
index 97633a55a..3ccc5503c 100644
--- a/lib/librte_eal/freebsd/eal/eal.c
+++ b/lib/librte_eal/freebsd/eal/eal.c
@@ -758,8 +758,6 @@ rte_eal_init(int argc, char **argv)
#endif
}
- rte_srand(rte_rdtsc());
-
/* in secondary processes, memory init may allocate additional fbarrays
* not present in primary processes, so to avoid any potential issues,
* initialize memzones first.
diff --git a/lib/librte_eal/linux/eal/Makefile b/lib/librte_eal/linux/eal/Makefile
index 6e5261152..729795a10 100644
--- a/lib/librte_eal/linux/eal/Makefile
+++ b/lib/librte_eal/linux/eal/Makefile
@@ -77,6 +77,7 @@ SRCS-$(CONFIG_RTE_EXEC_ENV_LINUX) += malloc_mp.c
SRCS-$(CONFIG_RTE_EXEC_ENV_LINUX) += rte_keepalive.c
SRCS-$(CONFIG_RTE_EXEC_ENV_LINUX) += rte_option.c
SRCS-$(CONFIG_RTE_EXEC_ENV_LINUX) += rte_service.c
+SRCS-$(CONFIG_RTE_EXEC_ENV_LINUX) += rte_random.c
SRCS-$(CONFIG_RTE_EXEC_ENV_LINUX) += rte_reciprocal.c
# from arch dir
diff --git a/lib/librte_eal/linux/eal/eal.c b/lib/librte_eal/linux/eal/eal.c
index d96ed3a7c..5f2083c4b 100644
--- a/lib/librte_eal/linux/eal/eal.c
+++ b/lib/librte_eal/linux/eal/eal.c
@@ -1122,8 +1122,6 @@ rte_eal_init(int argc, char **argv)
#endif
}
- rte_srand(rte_rdtsc());
-
if (rte_eal_log_init(logid, internal_config.syslog_facility) < 0) {
rte_eal_init_alert("Cannot init logging.");
rte_errno = ENOMEM;
diff --git a/lib/librte_eal/rte_eal_version.map b/lib/librte_eal/rte_eal_version.map
index 824edf0ff..20c1a9018 100644
--- a/lib/librte_eal/rte_eal_version.map
+++ b/lib/librte_eal/rte_eal_version.map
@@ -292,6 +292,8 @@ DPDK_19.08 {
rte_lcore_index;
rte_lcore_to_socket_id;
+ rte_rand;
+ rte_srand;
} DPDK_19.05;
--
2.17.1
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