From: Stephen Hemminger <stephen@networkplumber.org>
To: dev@dpdk.org
Cc: Stephen Hemminger <stephen@networkplumber.org>,
Nithin Dabilpuram <ndabilpuram@marvell.com>,
Kiran Kumar K <kirankumark@marvell.com>,
Sunil Kumar Kori <skori@marvell.com>,
Satha Rao <skoteshwar@marvell.com>,
Harman Kalra <hkalra@marvell.com>
Subject: [RFC 1/3] net/cnxk: add pause to spinloops
Date: Wed, 21 Jan 2026 10:05:42 -0800 [thread overview]
Message-ID: <20260121180845.889190-2-stephen@networkplumber.org> (raw)
In-Reply-To: <20260121180845.889190-1-stephen@networkplumber.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 <stephen@networkplumber.org>
---
drivers/net/cnxk/cn10k_tx.h | 4 ++--
drivers/net/cnxk/cn20k_tx.h | 4 ++--
2 files changed, 4 insertions(+), 4 deletions(-)
diff --git a/drivers/net/cnxk/cn10k_tx.h b/drivers/net/cnxk/cn10k_tx.h
index be9e020ac5..3f4cad168c 100644
--- a/drivers/net/cnxk/cn10k_tx.h
+++ b/drivers/net/cnxk/cn10k_tx.h
@@ -167,7 +167,7 @@ cn10k_nix_vwqe_wait_fc(struct cn10k_eth_txq *txq, uint16_t req)
#else
RTE_SET_USED(pkts);
while (rte_atomic_load_explicit(&txq->fc_cache_pkts, rte_memory_order_relaxed) < 0)
- ;
+ rte_pause();
#endif
cached = rte_atomic_fetch_sub_explicit(&txq->fc_cache_pkts, req, rte_memory_order_acquire) -
req;
@@ -402,7 +402,7 @@ cn10k_nix_sec_fc_wait(struct cn10k_eth_txq *txq, uint16_t nb_pkts)
#else
/* Wait for primary core to refill FC. */
while (rte_atomic_load_explicit(fc_sw, rte_memory_order_relaxed) < 0)
- ;
+ rte_pause();
#endif
val = rte_atomic_fetch_sub_explicit(fc_sw, nb_pkts, rte_memory_order_acquire) - nb_pkts;
diff --git a/drivers/net/cnxk/cn20k_tx.h b/drivers/net/cnxk/cn20k_tx.h
index 9e48744831..3dfad5fd5a 100644
--- a/drivers/net/cnxk/cn20k_tx.h
+++ b/drivers/net/cnxk/cn20k_tx.h
@@ -165,7 +165,7 @@ cn20k_nix_vwqe_wait_fc(struct cn20k_eth_txq *txq, uint16_t req)
#else
RTE_SET_USED(pkts);
while (rte_atomic_load_explicit(&txq->fc_cache_pkts, rte_memory_order_relaxed) < 0)
- ;
+ rte_pause();
#endif
cached = rte_atomic_fetch_sub_explicit(&txq->fc_cache_pkts, req, rte_memory_order_acquire) -
req;
@@ -392,7 +392,7 @@ cn20k_nix_sec_fc_wait(struct cn20k_eth_txq *txq, uint16_t nb_pkts)
#else
/* Wait for primary core to refill FC. */
while (rte_atomic_load_explicit(fc_sw, rte_memory_order_relaxed) < 0)
- ;
+ rte_pause();
#endif
val = rte_atomic_fetch_sub_explicit(fc_sw, nb_pkts, rte_memory_order_acquire) - nb_pkts;
--
2.51.0
next prev parent reply other threads:[~2026-01-21 18:08 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-01-21 18:05 [RFC 0/3] Add pause to empty spinloops Stephen Hemminger
2026-01-21 18:05 ` Stephen Hemminger [this message]
2026-01-21 18:05 ` [RFC 2/3] event/cnxk: add pause to spinloops Stephen Hemminger
2026-01-21 21:01 ` Stephen Hemminger
2026-01-21 18:05 ` [RFC 3/3] devtools/cocci: add script to find empty spinloops Stephen Hemminger
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