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Date: Thu, 24 Nov 2016 14:36:47 +0200
From: Tariq Toukan <ttoukan.linux@...il.com>
To: Eric Dumazet <eric.dumazet@...il.com>,
David Miller <davem@...emloft.net>
Cc: netdev <netdev@...r.kernel.org>, Tariq Toukan <tariqt@...lanox.com>
Subject: Re: [PATCH net-next] mlx4: reorganize struct mlx4_en_tx_ring
Hi Eric,
Thanks for your patch.
On 23/11/2016 1:56 AM, Eric Dumazet wrote:
> From: Eric Dumazet <edumazet@...gle.com>
>
> Goal is to reorganize this critical structure to increase performance.
>
> ndo_start_xmit() should only dirty one cache line, and access as few
> cache lines as possible.
>
> Add sp_ (Slow Path) prefix to fields that are not used in fast path,
> to make clear what is going on.
>
> After this patch pahole reports something much better, as all
> ndo_start_xmit() needed fields are packed into two cache lines instead
> of seven or eight
>
> struct mlx4_en_tx_ring {
> u32 last_nr_txbb; /* 0 0x4 */
> u32 cons; /* 0x4 0x4 */
> long unsigned int wake_queue; /* 0x8 0x8 */
> struct netdev_queue * tx_queue; /* 0x10 0x8 */
> u32 (*free_tx_desc)(struct mlx4_en_priv *, struct mlx4_en_tx_ring *, int, u8, u64, int); /* 0x18 0x8 */
> struct mlx4_en_rx_ring * recycle_ring; /* 0x20 0x8 */
>
> /* XXX 24 bytes hole, try to pack */
>
> /* --- cacheline 1 boundary (64 bytes) --- */
> u32 prod; /* 0x40 0x4 */
> unsigned int tx_dropped; /* 0x44 0x4 */
> long unsigned int bytes; /* 0x48 0x8 */
> long unsigned int packets; /* 0x50 0x8 */
> long unsigned int tx_csum; /* 0x58 0x8 */
> long unsigned int tso_packets; /* 0x60 0x8 */
> long unsigned int xmit_more; /* 0x68 0x8 */
> struct mlx4_bf bf; /* 0x70 0x18 */
> /* --- cacheline 2 boundary (128 bytes) was 8 bytes ago --- */
> __be32 doorbell_qpn; /* 0x88 0x4 */
> __be32 mr_key; /* 0x8c 0x4 */
> u32 size; /* 0x90 0x4 */
> u32 size_mask; /* 0x94 0x4 */
> u32 full_size; /* 0x98 0x4 */
> u32 buf_size; /* 0x9c 0x4 */
> void * buf; /* 0xa0 0x8 */
> struct mlx4_en_tx_info * tx_info; /* 0xa8 0x8 */
> int qpn; /* 0xb0 0x4 */
> u8 queue_index; /* 0xb4 0x1 */
> bool bf_enabled; /* 0xb5 0x1 */
> bool bf_alloced; /* 0xb6 0x1 */
> u8 hwtstamp_tx_type; /* 0xb7 0x1 */
> u8 * bounce_buf; /* 0xb8 0x8 */
> /* --- cacheline 3 boundary (192 bytes) --- */
> long unsigned int queue_stopped; /* 0xc0 0x8 */
> struct mlx4_hwq_resources sp_wqres; /* 0xc8 0x58 */
> /* --- cacheline 4 boundary (256 bytes) was 32 bytes ago --- */
> struct mlx4_qp sp_qp; /* 0x120 0x30 */
> /* --- cacheline 5 boundary (320 bytes) was 16 bytes ago --- */
> struct mlx4_qp_context sp_context; /* 0x150 0xf8 */
> /* --- cacheline 9 boundary (576 bytes) was 8 bytes ago --- */
> cpumask_t sp_affinity_mask; /* 0x248 0x20 */
> enum mlx4_qp_state sp_qp_state; /* 0x268 0x4 */
> u16 sp_stride; /* 0x26c 0x2 */
> u16 sp_cqn; /* 0x26e 0x2 */
>
> /* size: 640, cachelines: 10, members: 36 */
> /* sum members: 600, holes: 1, sum holes: 24 */
> /* padding: 16 */
> };
>
> Instead of this silly placement :
>
> struct mlx4_en_tx_ring {
> u32 last_nr_txbb; /* 0 0x4 */
> u32 cons; /* 0x4 0x4 */
> long unsigned int wake_queue; /* 0x8 0x8 */
>
> /* XXX 48 bytes hole, try to pack */
>
> /* --- cacheline 1 boundary (64 bytes) --- */
> u32 prod; /* 0x40 0x4 */
>
> /* XXX 4 bytes hole, try to pack */
>
> long unsigned int bytes; /* 0x48 0x8 */
> long unsigned int packets; /* 0x50 0x8 */
> long unsigned int tx_csum; /* 0x58 0x8 */
> long unsigned int tso_packets; /* 0x60 0x8 */
> long unsigned int xmit_more; /* 0x68 0x8 */
> unsigned int tx_dropped; /* 0x70 0x4 */
>
> /* XXX 4 bytes hole, try to pack */
>
> struct mlx4_bf bf; /* 0x78 0x18 */
> /* --- cacheline 2 boundary (128 bytes) was 16 bytes ago --- */
> long unsigned int queue_stopped; /* 0x90 0x8 */
> cpumask_t affinity_mask; /* 0x98 0x10 */
> struct mlx4_qp qp; /* 0xa8 0x30 */
> /* --- cacheline 3 boundary (192 bytes) was 24 bytes ago --- */
> struct mlx4_hwq_resources wqres; /* 0xd8 0x58 */
> /* --- cacheline 4 boundary (256 bytes) was 48 bytes ago --- */
> u32 size; /* 0x130 0x4 */
> u32 size_mask; /* 0x134 0x4 */
> u16 stride; /* 0x138 0x2 */
>
> /* XXX 2 bytes hole, try to pack */
>
> u32 full_size; /* 0x13c 0x4 */
> /* --- cacheline 5 boundary (320 bytes) --- */
> u16 cqn; /* 0x140 0x2 */
>
> /* XXX 2 bytes hole, try to pack */
>
> u32 buf_size; /* 0x144 0x4 */
> __be32 doorbell_qpn; /* 0x148 0x4 */
> __be32 mr_key; /* 0x14c 0x4 */
> void * buf; /* 0x150 0x8 */
> struct mlx4_en_tx_info * tx_info; /* 0x158 0x8 */
> struct mlx4_en_rx_ring * recycle_ring; /* 0x160 0x8 */
> u32 (*free_tx_desc)(struct mlx4_en_priv *, struct mlx4_en_tx_ring *, int, u8, u64, int); /* 0x168 0x8 */
> u8 * bounce_buf; /* 0x170 0x8 */
> struct mlx4_qp_context context; /* 0x178 0xf8 */
> /* --- cacheline 9 boundary (576 bytes) was 48 bytes ago --- */
> int qpn; /* 0x270 0x4 */
> enum mlx4_qp_state qp_state; /* 0x274 0x4 */
> u8 queue_index; /* 0x278 0x1 */
> bool bf_enabled; /* 0x279 0x1 */
> bool bf_alloced; /* 0x27a 0x1 */
>
> /* XXX 5 bytes hole, try to pack */
>
> /* --- cacheline 10 boundary (640 bytes) --- */
> struct netdev_queue * tx_queue; /* 0x280 0x8 */
> int hwtstamp_tx_type; /* 0x288 0x4 */
>
> /* size: 704, cachelines: 11, members: 36 */
> /* sum members: 587, holes: 6, sum holes: 65 */
> /* padding: 52 */
> };
>
>
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> ---
> drivers/net/ethernet/mellanox/mlx4/en_netdev.c | 2
> drivers/net/ethernet/mellanox/mlx4/en_tx.c | 48 +++++++--------
> drivers/net/ethernet/mellanox/mlx4/mlx4_en.h | 42 +++++++------
> 3 files changed, 48 insertions(+), 44 deletions(-)
>
> diff --git a/drivers/net/ethernet/mellanox/mlx4/en_netdev.c b/drivers/net/ethernet/mellanox/mlx4/en_netdev.c
> index 9a807e93c9fdd81e61e561208aa1480a244d0bdb..9018bb1b2e12142e048281a9d28ddf95e0023a61 100644
> --- a/drivers/net/ethernet/mellanox/mlx4/en_netdev.c
> +++ b/drivers/net/ethernet/mellanox/mlx4/en_netdev.c
> @@ -1305,7 +1305,7 @@ static void mlx4_en_tx_timeout(struct net_device *dev)
> if (!netif_tx_queue_stopped(netdev_get_tx_queue(dev, i)))
> continue;
> en_warn(priv, "TX timeout on queue: %d, QP: 0x%x, CQ: 0x%x, Cons: 0x%x, Prod: 0x%x\n",
> - i, tx_ring->qpn, tx_ring->cqn,
> + i, tx_ring->qpn, tx_ring->sp_cqn,
> tx_ring->cons, tx_ring->prod);
> }
>
> diff --git a/drivers/net/ethernet/mellanox/mlx4/en_tx.c b/drivers/net/ethernet/mellanox/mlx4/en_tx.c
> index 5de3cbe24f2bf467f9a8f7d499e131b6d2a1844c..4b597dca5c52d114344d638895275ed0d378bd96 100644
> --- a/drivers/net/ethernet/mellanox/mlx4/en_tx.c
> +++ b/drivers/net/ethernet/mellanox/mlx4/en_tx.c
> @@ -66,7 +66,7 @@ int mlx4_en_create_tx_ring(struct mlx4_en_priv *priv,
>
> ring->size = size;
> ring->size_mask = size - 1;
> - ring->stride = stride;
> + ring->sp_stride = stride;
> ring->full_size = ring->size - HEADROOM - MAX_DESC_TXBBS;
>
> tmp = size * sizeof(struct mlx4_en_tx_info);
> @@ -90,22 +90,22 @@ int mlx4_en_create_tx_ring(struct mlx4_en_priv *priv,
> goto err_info;
> }
> }
> - ring->buf_size = ALIGN(size * ring->stride, MLX4_EN_PAGE_SIZE);
> + ring->buf_size = ALIGN(size * ring->sp_stride, MLX4_EN_PAGE_SIZE);
>
> /* Allocate HW buffers on provided NUMA node */
> set_dev_node(&mdev->dev->persist->pdev->dev, node);
> - err = mlx4_alloc_hwq_res(mdev->dev, &ring->wqres, ring->buf_size);
> + err = mlx4_alloc_hwq_res(mdev->dev, &ring->sp_wqres, ring->buf_size);
> set_dev_node(&mdev->dev->persist->pdev->dev, mdev->dev->numa_node);
> if (err) {
> en_err(priv, "Failed allocating hwq resources\n");
> goto err_bounce;
> }
>
> - ring->buf = ring->wqres.buf.direct.buf;
> + ring->buf = ring->sp_wqres.buf.direct.buf;
>
> en_dbg(DRV, priv, "Allocated TX ring (addr:%p) - buf:%p size:%d buf_size:%d dma:%llx\n",
> ring, ring->buf, ring->size, ring->buf_size,
> - (unsigned long long) ring->wqres.buf.direct.map);
> + (unsigned long long) ring->sp_wqres.buf.direct.map);
>
> err = mlx4_qp_reserve_range(mdev->dev, 1, 1, &ring->qpn,
> MLX4_RESERVE_ETH_BF_QP);
> @@ -114,12 +114,12 @@ int mlx4_en_create_tx_ring(struct mlx4_en_priv *priv,
> goto err_hwq_res;
> }
>
> - err = mlx4_qp_alloc(mdev->dev, ring->qpn, &ring->qp, GFP_KERNEL);
> + err = mlx4_qp_alloc(mdev->dev, ring->qpn, &ring->sp_qp, GFP_KERNEL);
> if (err) {
> en_err(priv, "Failed allocating qp %d\n", ring->qpn);
> goto err_reserve;
> }
> - ring->qp.event = mlx4_en_sqp_event;
> + ring->sp_qp.event = mlx4_en_sqp_event;
>
> err = mlx4_bf_alloc(mdev->dev, &ring->bf, node);
> if (err) {
> @@ -141,7 +141,7 @@ int mlx4_en_create_tx_ring(struct mlx4_en_priv *priv,
> if (queue_index < priv->num_tx_rings_p_up)
> cpumask_set_cpu(cpumask_local_spread(queue_index,
> priv->mdev->dev->numa_node),
> - &ring->affinity_mask);
> + &ring->sp_affinity_mask);
>
> *pring = ring;
> return 0;
> @@ -149,7 +149,7 @@ int mlx4_en_create_tx_ring(struct mlx4_en_priv *priv,
> err_reserve:
> mlx4_qp_release_range(mdev->dev, ring->qpn, 1);
> err_hwq_res:
> - mlx4_free_hwq_res(mdev->dev, &ring->wqres, ring->buf_size);
> + mlx4_free_hwq_res(mdev->dev, &ring->sp_wqres, ring->buf_size);
> err_bounce:
> kfree(ring->bounce_buf);
> ring->bounce_buf = NULL;
> @@ -171,10 +171,10 @@ void mlx4_en_destroy_tx_ring(struct mlx4_en_priv *priv,
>
> if (ring->bf_alloced)
> mlx4_bf_free(mdev->dev, &ring->bf);
> - mlx4_qp_remove(mdev->dev, &ring->qp);
> - mlx4_qp_free(mdev->dev, &ring->qp);
> + mlx4_qp_remove(mdev->dev, &ring->sp_qp);
> + mlx4_qp_free(mdev->dev, &ring->sp_qp);
> mlx4_qp_release_range(priv->mdev->dev, ring->qpn, 1);
> - mlx4_free_hwq_res(mdev->dev, &ring->wqres, ring->buf_size);
> + mlx4_free_hwq_res(mdev->dev, &ring->sp_wqres, ring->buf_size);
> kfree(ring->bounce_buf);
> ring->bounce_buf = NULL;
> kvfree(ring->tx_info);
> @@ -190,7 +190,7 @@ int mlx4_en_activate_tx_ring(struct mlx4_en_priv *priv,
> struct mlx4_en_dev *mdev = priv->mdev;
> int err;
>
> - ring->cqn = cq;
> + ring->sp_cqn = cq;
> ring->prod = 0;
> ring->cons = 0xffffffff;
> ring->last_nr_txbb = 1;
> @@ -198,21 +198,21 @@ int mlx4_en_activate_tx_ring(struct mlx4_en_priv *priv,
> memset(ring->buf, 0, ring->buf_size);
> ring->free_tx_desc = mlx4_en_free_tx_desc;
>
> - ring->qp_state = MLX4_QP_STATE_RST;
> - ring->doorbell_qpn = cpu_to_be32(ring->qp.qpn << 8);
> + ring->sp_qp_state = MLX4_QP_STATE_RST;
> + ring->doorbell_qpn = cpu_to_be32(ring->sp_qp.qpn << 8);
> ring->mr_key = cpu_to_be32(mdev->mr.key);
>
> - mlx4_en_fill_qp_context(priv, ring->size, ring->stride, 1, 0, ring->qpn,
> - ring->cqn, user_prio, &ring->context);
> + mlx4_en_fill_qp_context(priv, ring->size, ring->sp_stride, 1, 0, ring->qpn,
> + ring->sp_cqn, user_prio, &ring->sp_context);
> if (ring->bf_alloced)
> - ring->context.usr_page =
> + ring->sp_context.usr_page =
> cpu_to_be32(mlx4_to_hw_uar_index(mdev->dev,
> ring->bf.uar->index));
>
> - err = mlx4_qp_to_ready(mdev->dev, &ring->wqres.mtt, &ring->context,
> - &ring->qp, &ring->qp_state);
> - if (!cpumask_empty(&ring->affinity_mask))
> - netif_set_xps_queue(priv->dev, &ring->affinity_mask,
> + err = mlx4_qp_to_ready(mdev->dev, &ring->sp_wqres.mtt, &ring->sp_context,
> + &ring->sp_qp, &ring->sp_qp_state);
> + if (!cpumask_empty(&ring->sp_affinity_mask))
> + netif_set_xps_queue(priv->dev, &ring->sp_affinity_mask,
> ring->queue_index);
>
> return err;
> @@ -223,8 +223,8 @@ void mlx4_en_deactivate_tx_ring(struct mlx4_en_priv *priv,
> {
> struct mlx4_en_dev *mdev = priv->mdev;
>
> - mlx4_qp_modify(mdev->dev, NULL, ring->qp_state,
> - MLX4_QP_STATE_RST, NULL, 0, 0, &ring->qp);
> + mlx4_qp_modify(mdev->dev, NULL, ring->sp_qp_state,
> + MLX4_QP_STATE_RST, NULL, 0, 0, &ring->sp_qp);
> }
>
> static inline bool mlx4_en_is_tx_ring_full(struct mlx4_en_tx_ring *ring)
> diff --git a/drivers/net/ethernet/mellanox/mlx4/mlx4_en.h b/drivers/net/ethernet/mellanox/mlx4/mlx4_en.h
> index eff21651b67308a17fe3d60d236cd0b6800a3fd2..574bcbb1b38fc4758511d8f7bd17a87b0a507a73 100644
> --- a/drivers/net/ethernet/mellanox/mlx4/mlx4_en.h
> +++ b/drivers/net/ethernet/mellanox/mlx4/mlx4_en.h
> @@ -281,46 +281,50 @@ struct mlx4_en_tx_ring {
> u32 last_nr_txbb;
> u32 cons;
> unsigned long wake_queue;
> + struct netdev_queue *tx_queue;
> + u32 (*free_tx_desc)(struct mlx4_en_priv *priv,
> + struct mlx4_en_tx_ring *ring,
> + int index, u8 owner,
> + u64 timestamp, int napi_mode);
> + struct mlx4_en_rx_ring *recycle_ring;
>
> /* cache line used and dirtied in mlx4_en_xmit() */
> u32 prod ____cacheline_aligned_in_smp;
> + unsigned int tx_dropped;
> unsigned long bytes;
> unsigned long packets;
> unsigned long tx_csum;
> unsigned long tso_packets;
> unsigned long xmit_more;
> - unsigned int tx_dropped;
> struct mlx4_bf bf;
> - unsigned long queue_stopped;
>
> /* Following part should be mostly read */
> - cpumask_t affinity_mask;
> - struct mlx4_qp qp;
> - struct mlx4_hwq_resources wqres;
> + __be32 doorbell_qpn;
> + __be32 mr_key;
> u32 size; /* number of TXBBs */
> u32 size_mask;
> - u16 stride;
> u32 full_size;
> - u16 cqn; /* index of port CQ associated with this ring */
> u32 buf_size;
> - __be32 doorbell_qpn;
> - __be32 mr_key;
> void *buf;
> struct mlx4_en_tx_info *tx_info;
> - struct mlx4_en_rx_ring *recycle_ring;
> - u32 (*free_tx_desc)(struct mlx4_en_priv *priv,
> - struct mlx4_en_tx_ring *ring,
> - int index, u8 owner,
> - u64 timestamp, int napi_mode);
> - u8 *bounce_buf;
> - struct mlx4_qp_context context;
> int qpn;
> - enum mlx4_qp_state qp_state;
> u8 queue_index;
> bool bf_enabled;
> bool bf_alloced;
> - struct netdev_queue *tx_queue;
> - int hwtstamp_tx_type;
> + u8 hwtstamp_tx_type;
> + u8 *bounce_buf;
> +
> + /* Not used in fast path
> + * Only queue_stopped might be used if BQL is not properly working.
> + */
> + unsigned long queue_stopped;
> + struct mlx4_hwq_resources sp_wqres;
> + struct mlx4_qp sp_qp;
> + struct mlx4_qp_context sp_context;
> + cpumask_t sp_affinity_mask;
> + enum mlx4_qp_state sp_qp_state;
> + u16 sp_stride;
> + u16 sp_cqn; /* index of port CQ associated with this ring */
> } ____cacheline_aligned_in_smp;
>
> struct mlx4_en_rx_desc {
>
>
Reviewed-by: Tariq Toukan <tariqt@...lanox.com>
Regards,
Tariq
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