IB/core: add max_send_sge and max_recv_sge attributes
This patch replaces the ib_device_attr.max_sge with max_send_sge and max_recv_sge. It allows ulps to take advantage of devices that have very different send and recv sge depths. For example cxgb4 has a max_recv_sge of 4, yet a max_send_sge of 16. Splitting out these attributes allows much more efficient use of the SQ for cxgb4 with ulps that use the RDMA_RW API. Consider a large RDMA WRITE that has 16 scattergather entries. With max_sge of 4, the ulp would send 4 WRITE WRs, but with max_sge of 16, it can be done with 1 WRITE WR. Acked-by: Sagi Grimberg <sagi@grimberg.me> Acked-by: Christoph Hellwig <hch@lst.de> Acked-by: Selvin Xavier <selvin.xavier@broadcom.com> Acked-by: Shiraz Saleem <shiraz.saleem@intel.com> Acked-by: Dennis Dalessandro <dennis.dalessandro@intel.com> Signed-off-by: Steve Wise <swise@opengridcomputing.com> Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
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Jason Gunthorpe

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commit
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@@ -888,7 +888,8 @@ static int mlx5_ib_query_device(struct ib_device *ibdev,
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max_sq_sg = (max_sq_desc - sizeof(struct mlx5_wqe_ctrl_seg) -
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sizeof(struct mlx5_wqe_raddr_seg)) /
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sizeof(struct mlx5_wqe_data_seg);
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props->max_sge = min(max_rq_sg, max_sq_sg);
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props->max_send_sge = max_sq_sg;
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props->max_recv_sge = max_rq_sg;
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props->max_sge_rd = MLX5_MAX_SGE_RD;
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props->max_cq = 1 << MLX5_CAP_GEN(mdev, log_max_cq);
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props->max_cqe = (1 << MLX5_CAP_GEN(mdev, log_max_cq_sz)) - 1;
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