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Wythe" , Sidraya Jayagond , Wenjia Zhang , Tony Lu , Wen Gu , netdev@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-rdma@vger.kernel.org, linux-s390@vger.kernel.org References: <20250904211254.1057445-1-pasic@linux.ibm.com> <20250904211254.1057445-2-pasic@linux.ibm.com> <20250905110059.450da664.pasic@linux.ibm.com> <20250905140135.2487a99f.pasic@linux.ibm.com> Content-Language: en-US From: Mahanta Jambigi In-Reply-To: <20250905140135.2487a99f.pasic@linux.ibm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUwODMwMDAzMCBTYWx0ZWRfX7KKUgk6iFVmQ yML+Za9UEJaK+LkX6q9Y6sXC/mI7Qe4Usq+3LxkrCCU7P3OfRz/gLft5ur6v/6xTXnpCxVyJNI3 yA1dDepUxB+GeT27a6naSMMsb7DTt5k1W40+FhOOibr5R0NCizHWmXkCK8bwk8vrpn+U7korLx3 i5TX4qRaFT2O/RAcU9ssN38Mmy9AMSfV5S5fkb/imS6Hzta7HVsk6AjQLQCbUfynpx47E2k+l4z hN0j6uVGGLzHTtBzvC6yzZnZMQBfaKXrB5kLD5w1SnlaxyZZekj2JyvXmahj9LV6HF4nXF6y8DY lyDCDgDuqK4CysgQyY4qXkUV5UikTXgCY9GMQYBXshDzgk3LHvC5MQvU65nbYKEpY5MlgiS8W0B R7SLhU1q X-Proofpoint-GUID: KpI3tt6SOYpnA3FHAmwT_cdd2oR219cy X-Proofpoint-ORIG-GUID: u9qEwTRx78snNTiQBN9ej4uJ3a6I2XJF X-Authority-Analysis: v=2.4 cv=Ao/u3P9P c=1 sm=1 tr=0 ts=68baefcd cx=c_pps a=5BHTudwdYE3Te8bg5FgnPg==:117 a=5BHTudwdYE3Te8bg5FgnPg==:17 a=IkcTkHD0fZMA:10 a=yJojWOMRYYMA:10 a=VnNF1IyMAAAA:8 a=B3rph_lr8uwRdQD9BfQA:9 a=QEXdDO2ut3YA:10 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1117,Hydra:6.1.9,FMLib:17.12.80.40 definitions=2025-09-05_04,2025-09-04_01,2025-03-28_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 clxscore=1011 phishscore=0 impostorscore=0 priorityscore=1501 spamscore=0 suspectscore=0 bulkscore=0 adultscore=0 malwarescore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2507300000 definitions=main-2508300030 On 05/09/25 5:31 pm, Halil Pasic wrote: > On Fri, 5 Sep 2025 11:00:59 +0200 > Halil Pasic wrote: > >>> 1. What if the two sides have different max_send_wr/max_recv_wr configurations? >>> IIUC, For example, if the client sets max_send_wr to 64, but the server sets >>> max_recv_wr to 16, the client might overflow the server's QP receive >>> queue, potentially causing an RNR (Receiver Not Ready) error. >> >> I don't think the 16 is spec-ed anywhere and if the client and the server >> need to agree on the same value it should either be speced, or a >> protocol mechanism for negotiating it needs to exist. So what is your >> take on this as an SMC maintainer? >> >> I think, we have tested heterogeneous setups and didn't see any grave >> issues. But let me please do a follow up on this. Maybe the other >> maintainers can chime in as well. > > Did some research and some thinking. Are you concerned about a > performance regression for e.g. 64 -> 16 compared to 16 -> 16? According > to my current understanding the RNR must not lead to a catastrophic > failure, but the RDMA/IB stack is supposed to handle that. > Hi Dust, I configured a client-server setup & did some SMC-R testing by setting the values you proposed. Ran iperf3(using smc_run) with max parallel connections of 128 & it looks good. No tcp fallback. No obvious errors. As Halil mentioned I don't see any catastrophic failure here. Let me know if I need to stress the system by some more tests or any specific test that you can think may cause RNR errors. The setup is ready & I can try it. *Client* side logs: [root@client ~]$ sysctl net.smc.smcr_max_send_wr net.smc.smcr_max_send_wr = 64 [root@client ~]$ [root@client ~]$ smc_run iperf3 -P 128 -t 120 -c 10.25.0.72 Connecting to host 10.25.0.72, port 5201 [ 5] local 10.25.0.73 port 52544 connected to 10.25.0.72 port 5201 [ 7] local 10.25.0.73 port 52558 connected to 10.25.0.72 port 5201 *Server* side logs: [root@server ~]$ sysctl net.smc.smcr_max_recv_wr net.smc.smcr_max_recv_wr = 16 [root@client ~]$ [root@server~]$ smc_run iperf3 -s ----------------------------------------------------------- Server listening on 5201 (test #1) -----------------------------------------------------------