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HE1PR0501MB2042; 6:ag0cb6VznJuKpBcK453zBMFAqqQ0Ujm3ZU+LDmPz1SQ7lnj4A5Lk0shHexOlLBol4mjHPseIH4U5LhyLf0Y+0rJmLqGUFPfPzhp3nkx7vg+SLbZgSrQ20gXaNPlMlVYg4tarTTLqWN8cwR3evJY9QyJOeeb+ke8N2KNp27zm2aaFxrm5zDkDRg92rbKAAyk9rV5+k70lF5CkSC0Z3ruo4Tatkopd30+BT8U2JQIDiGGVhQWji0twyahnMYhmqlOhqTIRXpXKyu27gXruh/7K5bjYwlmlgn3U8ZwrN7+KSaiahQpQ9BZ2UjfMUwrQNayY6Yw5ab85l+WMcwn9tb1k8nMVDM6Xb9tv22a9FGIe3FQ=; 5:+KMBDeMJkFWNnhMVTT6/J8JZ+zLuNPoIA3sJKxp+iL/HJc3iW8y1PKpkq/tvQfr0JmCFbw1C7/Swz2mYqLHbCFOxxIT45f/DI0aSetDHDtYDk/hWdZ+5z7oTYYPzY1vGW3DmBOm+50vSYEwlDJf9gTLd5q1iIxordHKGIgHYcVY=; 24:BBxQetGQx8LG3rCsgMnJng/jhxudKJd8blij6SBVXqKa9R8/R6aj7oLi1jgDKHkTqYhs6HTFLsd5kT1YXZITJZpR/X1RecaIbUk1bmNWUow=; 7:cVegS9Unh02idZGB63vBjeXQZseJxNDogsmg2CQb6P4U12m1JPOuK7crKD5u6hGZvZDsRqtDR7wJkh1EmIExOqvSt2iHvqM7sit273VJq2wjw8wXlxkE5SjDE0BCf3xTqdIlaM7D4UU6+JNiu6uXDXK0Vn6Jb3w0WJj6Kj4N5qXurAcOQF2AfvtAPEnFeGlgmQ/pU7Q2Q0N/tz1ndYKZXdPoJvkTdwD9u0qzltGBl2t5N/my7TtqsiK1GnWOBXoq SpamDiagnosticOutput: 1:99 SpamDiagnosticMetadata: NSPM X-OriginatorOrg: Mellanox.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 25 Oct 2017 00:27:39.0634 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: aaca270b-56e6-48bc-2897-08d51b3f33e0 X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: a652971c-7d2e-4d9b-a6a4-d149256f461b X-MS-Exchange-Transport-CrossTenantHeadersStamped: HE1PR0501MB2042 Subject: [dpdk-dev] [PATCH v2] net/mlx5: fix Tx doorbell memory barrier X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 25 Oct 2017 00:27:46 -0000 Configuring UAR as IO-mapped makes maximum throughput decline by noticeable amount. If UAR is configured as write-combining register, a write memory barrier is needed on ringing a doorbell. rte_wmb() is mostly effective when the size of a burst is comparatively small. Revert the register back to write-combining and enforce a write memory barrier instead, except for vectorized Tx burst routines. Application can change it by setting MLX5_SHUT_UP_BF under its own necessity. Fixes: 9f9bebae5530 ("net/mlx5: don't map doorbell register to write combining") Cc: stable@dpdk.org Cc: Sagi Grimberg Cc: Alexander Solganik Signed-off-by: Yongseok Koh Acked-by: Shahaf Shuler --- v2: * Add documentation. * Rename functions to minimize changes. doc/guides/nics/mlx5.rst | 17 +++++++++++++++++ drivers/net/mlx5/mlx5.c | 2 -- drivers/net/mlx5/mlx5_rxtx.h | 23 +++++++++++++++++++++-- drivers/net/mlx5/mlx5_rxtx_vec_neon.h | 2 +- drivers/net/mlx5/mlx5_rxtx_vec_sse.h | 2 +- 5 files changed, 40 insertions(+), 6 deletions(-) diff --git a/doc/guides/nics/mlx5.rst b/doc/guides/nics/mlx5.rst index d24941a22..085d3940c 100644 --- a/doc/guides/nics/mlx5.rst +++ b/doc/guides/nics/mlx5.rst @@ -171,6 +171,23 @@ Environment variables This is disabled by default since this can also decrease performance for unaligned packet sizes. +- ``MLX5_SHUT_UP_BF`` + + Configures HW Tx doorbell register as IO-mapped. + + By default, the HW Tx doorbell is configured as a write-combining register. + The register would be flushed to HW usually when the write-combining buffer + becomes full, but it depends on CPU design. + + Except for vectorized Tx burst routines, a write memory barrier is enforced + after updating the register so that the update can be immediately visible to + HW. + + When vectorized Tx burst is called, the barrier is set only if the burst size + is not aligned to MLX5_VPMD_TX_MAX_BURST. However, setting this environmental + variable will bring better latency even though the maximum throughput can + slightly decline. + Run-time configuration ~~~~~~~~~~~~~~~~~~~~~~ diff --git a/drivers/net/mlx5/mlx5.c b/drivers/net/mlx5/mlx5.c index 89fdc134f..fcdcbc367 100644 --- a/drivers/net/mlx5/mlx5.c +++ b/drivers/net/mlx5/mlx5.c @@ -1037,8 +1037,6 @@ rte_mlx5_pmd_init(void) * using this PMD, which is not supported in forked processes. */ setenv("RDMAV_HUGEPAGES_SAFE", "1", 1); - /* Don't map UAR to WC if BlueFlame is not used.*/ - setenv("MLX5_SHUT_UP_BF", "1", 1); /* Match the size of Rx completion entry to the size of a cacheline. */ if (RTE_CACHE_LINE_SIZE == 128) setenv("MLX5_CQE_SIZE", "128", 0); diff --git a/drivers/net/mlx5/mlx5_rxtx.h b/drivers/net/mlx5/mlx5_rxtx.h index ea037427b..d34f3cc04 100644 --- a/drivers/net/mlx5/mlx5_rxtx.h +++ b/drivers/net/mlx5/mlx5_rxtx.h @@ -578,15 +578,18 @@ mlx5_tx_mb2mr(struct mlx5_txq_data *txq, struct rte_mbuf *mb) } /** - * Ring TX queue doorbell. + * Ring TX queue doorbell and flush the update if requested. * * @param txq * Pointer to TX queue structure. * @param wqe * Pointer to the last WQE posted in the NIC. + * @param cond + * Request for write memory barrier after BlueFlame update. */ static __rte_always_inline void -mlx5_tx_dbrec(struct mlx5_txq_data *txq, volatile struct mlx5_wqe *wqe) +mlx5_tx_dbrec_cond_wmb(struct mlx5_txq_data *txq, volatile struct mlx5_wqe *wqe, + int cond) { uint64_t *dst = (uint64_t *)((uintptr_t)txq->bf_reg); volatile uint64_t *src = ((volatile uint64_t *)wqe); @@ -596,6 +599,22 @@ mlx5_tx_dbrec(struct mlx5_txq_data *txq, volatile struct mlx5_wqe *wqe) /* Ensure ordering between DB record and BF copy. */ rte_wmb(); *dst = *src; + if (cond) + rte_wmb(); +} + +/** + * Ring TX queue doorbell and flush the update by write memory barrier. + * + * @param txq + * Pointer to TX queue structure. + * @param wqe + * Pointer to the last WQE posted in the NIC. + */ +static __rte_always_inline void +mlx5_tx_dbrec(struct mlx5_txq_data *txq, volatile struct mlx5_wqe *wqe) +{ + mlx5_tx_dbrec_cond_wmb(txq, wqe, 1); } #endif /* RTE_PMD_MLX5_RXTX_H_ */ diff --git a/drivers/net/mlx5/mlx5_rxtx_vec_neon.h b/drivers/net/mlx5/mlx5_rxtx_vec_neon.h index 4cb7f2889..61f5bc45b 100644 --- a/drivers/net/mlx5/mlx5_rxtx_vec_neon.h +++ b/drivers/net/mlx5/mlx5_rxtx_vec_neon.h @@ -345,7 +345,7 @@ txq_burst_v(struct mlx5_txq_data *txq, struct rte_mbuf **pkts, uint16_t pkts_n, txq->wqe_ci += (nb_dword_in_hdr + pkts_n + (nb_dword_per_wqebb - 1)) / nb_dword_per_wqebb; /* Ring QP doorbell. */ - mlx5_tx_dbrec(txq, wqe); + mlx5_tx_dbrec_cond_wmb(txq, wqe, pkts_n < MLX5_VPMD_TX_MAX_BURST); return pkts_n; } diff --git a/drivers/net/mlx5/mlx5_rxtx_vec_sse.h b/drivers/net/mlx5/mlx5_rxtx_vec_sse.h index e9819b762..a53027d84 100644 --- a/drivers/net/mlx5/mlx5_rxtx_vec_sse.h +++ b/drivers/net/mlx5/mlx5_rxtx_vec_sse.h @@ -344,7 +344,7 @@ txq_burst_v(struct mlx5_txq_data *txq, struct rte_mbuf **pkts, uint16_t pkts_n, txq->wqe_ci += (nb_dword_in_hdr + pkts_n + (nb_dword_per_wqebb - 1)) / nb_dword_per_wqebb; /* Ring QP doorbell. */ - mlx5_tx_dbrec(txq, wqe); + mlx5_tx_dbrec_cond_wmb(txq, wqe, pkts_n < MLX5_VPMD_TX_MAX_BURST); return pkts_n; } -- 2.11.0