| Message ID | 20210930194031.3181989-1-eric.dumazet@gmail.com (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | [net-next] net/mlx4_en: avoid one cache line miss to ring doorbell | expand |
| Context | Check | Description |
|---|---|---|
| netdev/cover_letter | success | Link |
| netdev/fixes_present | success | Link |
| netdev/patch_count | success | Link |
| netdev/tree_selection | success | Clearly marked for net-next |
| netdev/subject_prefix | success | Link |
| netdev/cc_maintainers | warning | 1 maintainers not CCed: linux-rdma@vger.kernel.org |
| netdev/source_inline | success | Was 0 now: 0 |
| netdev/verify_signedoff | success | Link |
| netdev/module_param | success | Was 0 now: 0 |
| netdev/build_32bit | fail | Errors and warnings before: 0 this patch: 2 |
| netdev/kdoc | success | Errors and warnings before: 0 this patch: 0 |
| netdev/verify_fixes | success | Link |
| netdev/checkpatch | success | total: 0 errors, 0 warnings, 0 checks, 23 lines checked |
| netdev/build_allmodconfig_warn | fail | Errors and warnings before: 0 this patch: 2 |
| netdev/header_inline | success | Link |
On Thu, 30 Sep 2021 12:40:31 -0700 Eric Dumazet wrote: > From: Eric Dumazet <edumazet@google.com> > > This patch caches doorbell address directly in struct mlx4_en_tx_ring. > > This removes the need to bring in cpu caches whole struct mlx4_uar > in fast path. > > Note that mlx4_uar is not guaranteed to be on a local node, > because mlx4_bf_alloc() uses a single free list (priv->bf_list) > regardless of its node parameter. > > This kind of change does matter in presence of light/moderate traffic. > In high stress, this read-only line would be kept hot in caches. > > Signed-off-by: Eric Dumazet <edumazet@google.com> > Cc: Tariq Toukan <tariqt@nvidia.com> > /* Following part should be mostly read */ > + void *doorbell_address; We'll need to make sparse happy before applying: drivers/net/ethernet/mellanox/mlx4/en_tx.c:133:32: warning: incorrect type in assignment (different address spaces) drivers/net/ethernet/mellanox/mlx4/en_tx.c:133:32: expected void *doorbell_address drivers/net/ethernet/mellanox/mlx4/en_tx.c:133:32: got void [noderef] __iomem * drivers/net/ethernet/mellanox/mlx4/en_tx.c:757:56: warning: incorrect type in argument 2 (different address spaces) drivers/net/ethernet/mellanox/mlx4/en_tx.c:757:56: expected void [noderef] __iomem * drivers/net/ethernet/mellanox/mlx4/en_tx.c:757:56: got void *doorbell_address
On Thu, Sep 30, 2021 at 5:10 PM Jakub Kicinski <kuba@kernel.org> wrote: > > On Thu, 30 Sep 2021 12:40:31 -0700 Eric Dumazet wrote: > > From: Eric Dumazet <edumazet@google.com> > > > > This patch caches doorbell address directly in struct mlx4_en_tx_ring. > > > > This removes the need to bring in cpu caches whole struct mlx4_uar > > in fast path. > > > > Note that mlx4_uar is not guaranteed to be on a local node, > > because mlx4_bf_alloc() uses a single free list (priv->bf_list) > > regardless of its node parameter. > > > > This kind of change does matter in presence of light/moderate traffic. > > In high stress, this read-only line would be kept hot in caches. > > > > Signed-off-by: Eric Dumazet <edumazet@google.com> > > Cc: Tariq Toukan <tariqt@nvidia.com> > > > /* Following part should be mostly read */ > > + void *doorbell_address; > > We'll need to make sparse happy before applying: > > drivers/net/ethernet/mellanox/mlx4/en_tx.c:133:32: warning: incorrect type in assignment (different address spaces) > drivers/net/ethernet/mellanox/mlx4/en_tx.c:133:32: expected void *doorbell_address > drivers/net/ethernet/mellanox/mlx4/en_tx.c:133:32: got void [noderef] __iomem * > drivers/net/ethernet/mellanox/mlx4/en_tx.c:757:56: warning: incorrect type in argument 2 (different address spaces) > drivers/net/ethernet/mellanox/mlx4/en_tx.c:757:56: expected void [noderef] __iomem * > drivers/net/ethernet/mellanox/mlx4/en_tx.c:757:56: got void *doorbell_address Yes indeed, I'll send a V2 right away, thanks !
diff --git a/drivers/net/ethernet/mellanox/mlx4/en_tx.c b/drivers/net/ethernet/mellanox/mlx4/en_tx.c index c56b9dba4c71898b61e87fd32e5fa523c313e445..817f4154b86d599cd593876ec83529051d95fe2f 100644 --- a/drivers/net/ethernet/mellanox/mlx4/en_tx.c +++ b/drivers/net/ethernet/mellanox/mlx4/en_tx.c @@ -130,6 +130,7 @@ int mlx4_en_create_tx_ring(struct mlx4_en_priv *priv, ring->bf_enabled = !!(priv->pflags & MLX4_EN_PRIV_FLAGS_BLUEFLAME); } + ring->doorbell_address = ring->bf.uar->map + MLX4_SEND_DOORBELL; ring->hwtstamp_tx_type = priv->hwtstamp_config.tx_type; ring->queue_index = queue_index; @@ -753,8 +754,7 @@ void mlx4_en_xmit_doorbell(struct mlx4_en_tx_ring *ring) #else iowrite32be( #endif - (__force u32)ring->doorbell_qpn, - ring->bf.uar->map + MLX4_SEND_DOORBELL); + (__force u32)ring->doorbell_qpn, ring->doorbell_address); } static void mlx4_en_tx_write_desc(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 ad0a8b488832c8cdca2790e47fc778fe15686f7f..e1ad64cc0c8784352d18ae89df6d05bd9709e8a0 100644 --- a/drivers/net/ethernet/mellanox/mlx4/mlx4_en.h +++ b/drivers/net/ethernet/mellanox/mlx4/mlx4_en.h @@ -283,6 +283,7 @@ struct mlx4_en_tx_ring { struct mlx4_bf bf; /* Following part should be mostly read */ + void *doorbell_address; __be32 doorbell_qpn; __be32 mr_key; u32 size; /* number of TXBBs */