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([2601:647:4000:d7:2590:9462:ff8a:101f]) by smtp.gmail.com with ESMTPSA id i8sm12213935pgr.82.2020.05.25.14.51.26 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 25 May 2020 14:51:27 -0700 (PDT) Subject: Re: [PATCH v2 4/4] RDMA/srpt: Increase max_send_sge From: Bart Van Assche To: Leon Romanovsky Cc: Jason Gunthorpe , Doug Ledford , linux-rdma@vger.kernel.org, Laurence Oberman , Kamal Heib References: <20200525172212.14413-1-bvanassche@acm.org> <20200525172212.14413-5-bvanassche@acm.org> <20200525175152.GI10591@unreal> <8633b4b8-fb7d-8034-e2ac-789ec61f4c67@acm.org> Autocrypt: addr=bvanassche@acm.org; prefer-encrypt=mutual; keydata= mQENBFSOu4oBCADcRWxVUvkkvRmmwTwIjIJvZOu6wNm+dz5AF4z0FHW2KNZL3oheO3P8UZWr LQOrCfRcK8e/sIs2Y2D3Lg/SL7qqbMehGEYcJptu6mKkywBfoYbtBkVoJ/jQsi2H0vBiiCOy fmxMHIPcYxaJdXxrOG2UO4B60Y/BzE6OrPDT44w4cZA9DH5xialliWU447Bts8TJNa3lZKS1 AvW1ZklbvJfAJJAwzDih35LxU2fcWbmhPa7EO2DCv/LM1B10GBB/oQB5kvlq4aA2PSIWkqz4 3SI5kCPSsygD6wKnbRsvNn2mIACva6VHdm62A7xel5dJRfpQjXj2snd1F/YNoNc66UUTABEB AAG0JEJhcnQgVmFuIEFzc2NoZSA8YnZhbmFzc2NoZUBhY20ub3JnPokBOQQTAQIAIwUCVI67 igIbAwcLCQgHAwIBBhUIAgkKCwQWAgMBAh4BAheAAAoJEHFcPTXFzhAJ8QkH/1AdXblKL65M Y1Zk1bYKnkAb4a98LxCPm/pJBilvci6boefwlBDZ2NZuuYWYgyrehMB5H+q+Kq4P0IBbTqTa jTPAANn62A6jwJ0FnCn6YaM9TZQjM1F7LoDX3v+oAkaoXuq0dQ4hnxQNu792bi6QyVdZUvKc macVFVgfK9n04mL7RzjO3f+X4midKt/s+G+IPr4DGlrq+WH27eDbpUR3aYRk8EgbgGKvQFdD CEBFJi+5ZKOArmJVBSk21RHDpqyz6Vit3rjep7c1SN8s7NhVi9cjkKmMDM7KYhXkWc10lKx2 RTkFI30rkDm4U+JpdAd2+tP3tjGf9AyGGinpzE2XY1K5AQ0EVI67igEIAKiSyd0nECrgz+H5 PcFDGYQpGDMTl8MOPCKw/F3diXPuj2eql4xSbAdbUCJzk2ETif5s3twT2ER8cUTEVOaCEUY3 eOiaFgQ+nGLx4BXqqGewikPJCe+UBjFnH1m2/IFn4T9jPZkV8xlkKmDUqMK5EV9n3eQLkn5g lco+FepTtmbkSCCjd91EfThVbNYpVQ5ZjdBCXN66CKyJDMJ85HVr5rmXG/nqriTh6cv1l1Js T7AFvvPjUPknS6d+BETMhTkbGzoyS+sywEsQAgA+BMCxBH4LvUmHYhpS+W6CiZ3ZMxjO8Hgc ++w1mLeRUvda3i4/U8wDT3SWuHcB3DWlcppECLkAEQEAAYkBHwQYAQIACQUCVI67igIbDAAK CRBxXD01xc4QCZ4dB/0QrnEasxjM0PGeXK5hcZMT9Eo998alUfn5XU0RQDYdwp6/kMEXMdmT oH0F0xB3SQ8WVSXA9rrc4EBvZruWQ+5/zjVrhhfUAx12CzL4oQ9Ro2k45daYaonKTANYG22y //x8dLe2Fv1By4SKGhmzwH87uXxbTJAUxiWIi1np0z3/RDnoVyfmfbbL1DY7zf2hYXLLzsJR mSsED/1nlJ9Oq5fALdNEPgDyPUerqHxcmIub+pF0AzJoYHK5punqpqfGmqPbjxrJLPJfHVKy goMj5DlBMoYqEgpbwdUYkH6QdizJJCur4icy8GUNbisFYABeoJ91pnD4IGei3MTdvINSZI5e Message-ID: <0ca86214-372d-eefe-d259-d50d1e18f096@acm.org> Date: Mon, 25 May 2020 14:51:25 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.8.0 MIME-Version: 1.0 In-Reply-To: <8633b4b8-fb7d-8034-e2ac-789ec61f4c67@acm.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-rdma-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-rdma@vger.kernel.org On 2020-05-25 12:15, Bart Van Assche wrote: > On 2020-05-25 10:51, Leon Romanovsky wrote: >> On Mon, May 25, 2020 at 10:22:12AM -0700, Bart Van Assche wrote: >>> The ib_srpt driver limits max_send_sge to 16. Since that is a workaround >>> for an mlx4 bug that has been fixed, increase max_send_sge. For mlx4, do >>> not use the value advertised by the driver (32) since that causes QP's >>> to transition to the error status. >> >> How are you avoiding mlx4 bug in this patch? >> Isn't "attrs->max_send_sge" come from driver as is? > > Hi Leon, > > Development of this patch started considerable time ago - before the > ib_srpt driver was converted to the RDMA R/W API. Before that conversion > the ib_srpt driver was using attrs->max_send_sge limit for both RDMA > writes and RDMA reads, which is wrong. Hence the need for the > "max_sge_delta" parameter (max_send_sge = 32 and max_sge_rd = 30 for > mlx4). The following code from drivers/infiniband/core/rw.c selects the > proper limit: > > u32 max_sge = dir == DMA_TO_DEVICE ? qp->max_write_sge : > qp->max_read_sge; > > The following code in drivers/infiniband/core/verbs.c sets these limits: > > qp->max_write_sge = qp_init_attr->cap.max_send_sge; > qp->max_read_sge = min_t(u32, qp_init_attr->cap.max_send_sge, > device->attrs.max_sge_rd); The commit message should be shortened to the following: "The ib_srpt driver limits max_send_sge to 16. Since that is a workaround for an mlx4 bug that has been fixed, increase max_send_sge. See also commit f95ccffc715b ("IB/mlx4: Use 4K pages for kernel QP's WQE buffer")." Bart.