The rte_rand() documentation left it unspecified if the rte_rand() was
multi-thread safe or not, and the implementation (based on lrand48())
was not.
This commit makes rte_rand() safe to use from any lcore thread by
using lrand48_r() and per-lcore random state structs. Besides the
obvious improvement in terms of correctness (for concurrent users),
this also much improves rte_rand() performance, since the threads no
longer shares state. For the single-threaded case, this patch causes
~10% rte_rand() performance degradation.
rte_srand() is left multi-thread unsafe, and external synchronization
is required to serialize rte_sand() calls from different lcore
threads, and a rte_srand() call with rte_rand() calls made by other
lcore threads.
The assumption is that the random number generators will be seeded
once, during startup.
Bugzilla ID: 114
Signed-off-by: Mattias Rönnblom <mattias.ronnb...@ericsson.com>
---
lib/librte_eal/common/include/rte_random.h | 25 ++++-----
lib/librte_eal/common/meson.build | 1 +
lib/librte_eal/common/rte_random.c | 65 ++++++++++++++++++++++
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 +
8 files changed, 80 insertions(+), 19 deletions(-)
create mode 100644 lib/librte_eal/common/rte_random.c
diff --git a/lib/librte_eal/common/include/rte_random.h
b/lib/librte_eal/common/include/rte_random.h
index b2ca1c209..bca85a672 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.
@@ -25,14 +24,15 @@ 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.
@@ -41,18 +41,13 @@ rte_srand(uint64_t seedval)
* congruential algorithm and 48-bit integer arithmetic, called twice
* to generate a 64-bit value.
*
+ * 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..9d519d03b
--- /dev/null
+++ b/lib/librte_eal/common/rte_random.c
@@ -0,0 +1,65 @@
+/* SPDX-License-Identifier: BSD-3-Clause
+ * Copyright(c) 2010-2014 Intel Corporation
+ * Copyright(c) 2019 Ericsson AB
+ */
+
+#include <stdlib.h>
+
+#include <rte_cycles.h>
+#include <rte_eal.h>
+#include <rte_lcore.h>
+#include <rte_random.h>
+
+struct rte_rand_data
+{
+ struct drand48_data data;
+} __rte_cache_aligned;
+
+static struct rte_rand_data rand_data[RTE_MAX_LCORE];
+
+void
+rte_srand(uint64_t seedval)
+{
+ unsigned i;
+
+ /* give the different lcores a different seed, to avoid a
+ situation where they generate the same sequence */
+ for (i = 0; i < RTE_MAX_LCORE; i++)
+ srand48_r((long)seedval + i, &rand_data[i].data);
+}
+
+static inline uint32_t
+__rte_rand48(struct drand48_data *data)
+{
+ long res;
+
+ lrand48_r(data, &res);
+
+ return (uint32_t)res;
+}
+
+uint64_t
+rte_rand(void)
+{
+ unsigned lcore_id;
+ struct drand48_data *data;
+ uint64_t val;
+
+ lcore_id = rte_lcore_id();
+
+ if (unlikely(lcore_id == LCORE_ID_ANY))
+ lcore_id = rte_get_master_lcore();
+
+ data = &rand_data[lcore_id].data;
+
+ val = __rte_rand48(data);
+ val <<= 32;
+ val += __rte_rand48(data);
+
+ return val;
+}
+
+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 c6ac9028f..5d43310b3 100644
--- a/lib/librte_eal/freebsd/eal/eal.c
+++ b/lib/librte_eal/freebsd/eal/eal.c
@@ -727,8 +727,6 @@ 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 f7ae62d7b..c2bdf0a67 100644
--- a/lib/librte_eal/linux/eal/eal.c
+++ b/lib/librte_eal/linux/eal/eal.c
@@ -1083,8 +1083,6 @@ 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 d6e375135..0d60668fa 100644
--- a/lib/librte_eal/rte_eal_version.map
+++ b/lib/librte_eal/rte_eal_version.map
@@ -366,10 +366,12 @@ EXPERIMENTAL {
rte_mp_request_async;
rte_mp_sendmsg;
rte_option_register;
+ rte_rand;
rte_realloc_socket;
rte_service_lcore_attr_get;
rte_service_lcore_attr_reset_all;
rte_service_may_be_active;
rte_socket_count;
rte_socket_id_by_idx;
+ rte_srand;
};
--
2.17.1
