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[204.195.96.226]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-48042c2ed5fsm29093565e9.8.2026.01.21.10.08.52 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 21 Jan 2026 10:08:53 -0800 (PST) From: Stephen Hemminger To: dev@dpdk.org Cc: Stephen Hemminger , Pavan Nikhilesh , Shijith Thotton Subject: [RFC 2/3] event/cnxk: add pause to spinloops Date: Wed, 21 Jan 2026 10:05:43 -0800 Message-ID: <20260121180845.889190-3-stephen@networkplumber.org> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20260121180845.889190-1-stephen@networkplumber.org> References: <20260121180845.889190-1-stephen@networkplumber.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org On SMT systems when a spinloop is done without a pause it may cause excessive latency. This problem was found by the fix_empty_spinloops coccinelle script. This is compile tested only! I don't have this hardware. Signed-off-by: Stephen Hemminger --- drivers/event/cnxk/cn10k_worker.c | 2 +- drivers/event/cnxk/cn20k_worker.c | 2 +- drivers/event/cnxk/cnxk_tim_worker.h | 4 ++-- 3 files changed, 4 insertions(+), 4 deletions(-) diff --git a/drivers/event/cnxk/cn10k_worker.c b/drivers/event/cnxk/cn10k_worker.c index 80077ec8a1..69ac67115a 100644 --- a/drivers/event/cnxk/cn10k_worker.c +++ b/drivers/event/cnxk/cn10k_worker.c @@ -93,7 +93,7 @@ sso_lmt_aw_wait_fc(struct cn10k_sso_hws *ws, int64_t req) retry: while (rte_atomic_load_explicit(ws->fc_cache_space, rte_memory_order_relaxed) < 0) - ; + rte_pause(); cached = rte_atomic_fetch_sub_explicit(ws->fc_cache_space, req, rte_memory_order_acquire) - req; diff --git a/drivers/event/cnxk/cn20k_worker.c b/drivers/event/cnxk/cn20k_worker.c index 53daf3b4b0..49dfb2a28c 100644 --- a/drivers/event/cnxk/cn20k_worker.c +++ b/drivers/event/cnxk/cn20k_worker.c @@ -93,7 +93,7 @@ sso_lmt_aw_wait_fc(struct cn20k_sso_hws *ws, int64_t req) retry: while (rte_atomic_load_explicit(ws->fc_cache_space, rte_memory_order_relaxed) < 0) - ; + rte_pause(); cached = rte_atomic_fetch_sub_explicit(ws->fc_cache_space, req, rte_memory_order_acquire) - req; diff --git a/drivers/event/cnxk/cnxk_tim_worker.h b/drivers/event/cnxk/cnxk_tim_worker.h index 09f84091ab..887c0800e2 100644 --- a/drivers/event/cnxk/cnxk_tim_worker.h +++ b/drivers/event/cnxk/cnxk_tim_worker.h @@ -405,9 +405,9 @@ cnxk_tim_add_entry_mp(struct cnxk_tim_ring *const tim_ring, : [crem] "r"(&bkt->w1) : "memory"); #else - while (rte_atomic_load_explicit((int64_t __rte_atomic *)&bkt->w1, + while (rte_atomic_load_explicit((int64_t __rte_atomic *)&bkt->w1, rte_memory_order_relaxed) < 0) - ; + rte_pause(); #endif goto __retry; } else if (!rem) { -- 2.51.0