From: "Mattias Rönnblom" <mattias.ronnblom@ericsson.com>
To: Thomas Monjalon <thomas@monjalon.net>,
David Marchand <david.marchand@redhat.com>
Cc: dev@dpdk.org, "Mattias Rönnblom" <mattias.ronnblom@ericsson.com>
Subject: [PATCH] eal: have unregistered non-EAL threads use dedicated PRNG
Date: Mon, 5 Dec 2022 11:03:34 +0100 [thread overview]
Message-ID: <20221205100334.3500-1-mattias.ronnblom@ericsson.com> (raw)
Prior to this change, unregistered non-EAL threads shared a PRNG
instance with the main lcore. The main lcore may well be used for fast
path processing, potentially making rte_rand() calls in the
process. It should not need to synchronize with control threads.
With this change, all unregistered non-EAL threads share one dedicated
PRNG instance.
The API documentation is updated to use the proper terminology when
referring to threads equipped with an lcore id.
Signed-off-by: Mattias Rönnblom <mattias.ronnblom@ericsson.com>
---
lib/eal/common/rte_random.c | 17 +++++++++++------
lib/eal/include/rte_random.h | 10 +++++++---
2 files changed, 18 insertions(+), 9 deletions(-)
diff --git a/lib/eal/common/rte_random.c b/lib/eal/common/rte_random.c
index 166b0d8921..565f2401ce 100644
--- a/lib/eal/common/rte_random.c
+++ b/lib/eal/common/rte_random.c
@@ -20,7 +20,11 @@ struct rte_rand_state {
uint64_t z5;
} __rte_cache_aligned;
-static struct rte_rand_state rand_states[RTE_MAX_LCORE];
+/* One instance each for every lcore id-equipped thread, and one
+ * additional instance to be shared by all others threads (i.e., all
+ * unregistered non-EAL threads).
+ */
+static struct rte_rand_state rand_states[RTE_MAX_LCORE + 1];
static uint32_t
__rte_rand_lcg32(uint32_t *seed)
@@ -114,14 +118,15 @@ __rte_rand_lfsr258(struct rte_rand_state *state)
static __rte_always_inline
struct rte_rand_state *__rte_rand_get_state(void)
{
- unsigned int lcore_id;
+ unsigned int idx;
- lcore_id = rte_lcore_id();
+ idx = rte_lcore_id();
- if (unlikely(lcore_id == LCORE_ID_ANY))
- lcore_id = rte_get_main_lcore();
+ /* last instance reserved for unregistered non-EAL threads */
+ if (unlikely(idx == LCORE_ID_ANY))
+ idx = RTE_MAX_LCORE;
- return &rand_states[lcore_id];
+ return &rand_states[idx];
}
uint64_t
diff --git a/lib/eal/include/rte_random.h b/lib/eal/include/rte_random.h
index d90e4d2192..2edf5d210b 100644
--- a/lib/eal/include/rte_random.h
+++ b/lib/eal/include/rte_random.h
@@ -41,7 +41,8 @@ rte_srand(uint64_t seedval);
*
* The generator is not cryptographically secure.
*
- * If called from lcore threads, this function is thread-safe.
+ * If called from EAL threads or registered non-EAL threads, this function
+ * is thread-safe.
*
* @return
* A pseudo-random value between 0 and (1<<64)-1.
@@ -55,7 +56,8 @@ rte_rand(void);
* 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.
+ * If called from EAL threads or registered non-EAL threads, this function
+ * is thread-safe.
*
* @param upper_bound
* The upper bound of the generated number.
@@ -75,7 +77,9 @@ rte_rand_max(uint64_t upper_bound);
* number uniformly distributed over the interval [0.0, 1.0).
*
* The generator is not cryptographically secure.
- * If called from lcore threads, this function is thread-safe.
+ *
+ * If called from EAL threads or registered non-EAL threads, this function
+ * is thread-safe.
*
* @return
* A pseudo-random value between 0 and 1.0.
--
2.34.1
next reply other threads:[~2022-12-05 10:08 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-12-05 10:03 Mattias Rönnblom [this message]
2022-12-05 10:58 ` Morten Brørup
2022-12-06 15:14 ` Mattias Rönnblom
2023-02-10 11:44 ` David Marchand
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