From e484ccddbe1b41886fef1e445ef2fdfa55086198 Mon Sep 17 00:00:00 2001 From: Nikhil Rao Date: Mon, 16 Sep 2019 15:31:02 +0530 Subject: [PATCH] service: avoid false sharing on core state For a valid service, the core mask of the service is checked against the current core and the corresponding entry in the active_on_lcore array is set or reset. Upto 8 cores share the same cache line for their service active_on_lcore array entries since each entry is a uint8_t. Some number of these entries also share the cache line with the internal_flags member of struct rte_service_spec_impl, hence this false sharing also makes the service_valid() check expensive. Eliminate false sharing by moving the active_on_lcore array to a per-core data structure. The array is now indexed by service id. Signed-off-by: Nikhil Rao Acked-by: Gage Eads Acked-by: Harry van Haaren --- lib/librte_eal/common/rte_service.c | 16 +++++++--------- 1 file changed, 7 insertions(+), 9 deletions(-) diff --git a/lib/librte_eal/common/rte_service.c b/lib/librte_eal/common/rte_service.c index fe09077200..beb9691b23 100644 --- a/lib/librte_eal/common/rte_service.c +++ b/lib/librte_eal/common/rte_service.c @@ -51,7 +51,6 @@ struct rte_service_spec_impl { rte_atomic32_t num_mapped_cores; uint64_t calls; uint64_t cycles_spent; - uint8_t active_on_lcore[RTE_MAX_LCORE]; } __rte_cache_aligned; /* the internal values of a service core */ @@ -60,7 +59,7 @@ struct core_state { uint64_t service_mask; uint8_t runstate; /* running or stopped */ uint8_t is_service_core; /* set if core is currently a service core */ - + uint8_t service_active_on_lcore[RTE_SERVICE_NUM_MAX]; uint64_t loops; uint64_t calls_per_service[RTE_SERVICE_NUM_MAX]; } __rte_cache_aligned; @@ -344,7 +343,7 @@ rte_service_runner_do_callback(struct rte_service_spec_impl *s, static inline int32_t -service_run(uint32_t i, int lcore, struct core_state *cs, uint64_t service_mask) +service_run(uint32_t i, struct core_state *cs, uint64_t service_mask) { if (!service_valid(i)) return -EINVAL; @@ -352,11 +351,11 @@ service_run(uint32_t i, int lcore, struct core_state *cs, uint64_t service_mask) if (s->comp_runstate != RUNSTATE_RUNNING || s->app_runstate != RUNSTATE_RUNNING || !(service_mask & (UINT64_C(1) << i))) { - s->active_on_lcore[lcore] = 0; + cs->service_active_on_lcore[i] = 0; return -ENOEXEC; } - s->active_on_lcore[lcore] = 1; + cs->service_active_on_lcore[i] = 1; /* check do we need cmpset, if MT safe or <= 1 core * mapped, atomic ops are not required. @@ -379,7 +378,6 @@ int32_t rte_service_may_be_active(uint32_t id) { uint32_t ids[RTE_MAX_LCORE] = {0}; - struct rte_service_spec_impl *s = &rte_services[id]; int32_t lcore_count = rte_service_lcore_list(ids, RTE_MAX_LCORE); int i; @@ -387,7 +385,7 @@ rte_service_may_be_active(uint32_t id) return -EINVAL; for (i = 0; i < lcore_count; i++) { - if (s->active_on_lcore[ids[i]]) + if (lcore_states[i].service_active_on_lcore[id]) return 1; } @@ -418,7 +416,7 @@ rte_service_run_iter_on_app_lcore(uint32_t id, uint32_t serialize_mt_unsafe) return -EBUSY; } - int ret = service_run(id, rte_lcore_id(), cs, UINT64_MAX); + int ret = service_run(id, cs, UINT64_MAX); if (serialize_mt_unsafe) rte_atomic32_dec(&s->num_mapped_cores); @@ -439,7 +437,7 @@ rte_service_runner_func(void *arg) for (i = 0; i < RTE_SERVICE_NUM_MAX; i++) { /* return value ignored as no change to code flow */ - service_run(i, lcore, cs, service_mask); + service_run(i, cs, service_mask); } cs->loops++;