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Wythe" , dust.li@linux.alibaba.com, kuba@kernel.org, davem@davemloft.net, netdev@vger.kernel.org, linux-s390@vger.kernel.org, linux-rdma@vger.kernel.org References: <1641301961-59331-1-git-send-email-alibuda@linux.alibaba.com> <8a60dabb-1799-316c-80b5-14c920fe98ab@linux.ibm.com> <20220105044049.GA107642@e02h04389.eu6sqa> <20220105085748.GD31579@linux.alibaba.com> <20220105150612.GA75522@e02h04389.eu6sqa> <5a5ba1b6-93d7-5c1e-aab2-23a52727fbd1@linux.ibm.com> From: Stefan Raspl In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-GUID: dsBJzItTA-47pkbs7Bd9WYnuSK2Smar3 X-Proofpoint-ORIG-GUID: K6gQPcKdjNxaAW_w8gQ53t0SKhqEEu98 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.205,Aquarius:18.0.816,Hydra:6.0.425,FMLib:17.11.62.513 definitions=2022-01-20_06,2022-01-20_01,2021-12-02_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 mlxlogscore=999 impostorscore=0 phishscore=0 lowpriorityscore=0 clxscore=1011 adultscore=0 mlxscore=0 suspectscore=0 bulkscore=0 spamscore=0 malwarescore=0 priorityscore=1501 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2110150000 definitions=main-2201200081 Precedence: bulk List-ID: X-Mailing-List: linux-rdma@vger.kernel.org On 1/20/22 14:39, Tony Lu wrote: > On Thu, Jan 13, 2022 at 09:07:51AM +0100, Karsten Graul wrote: >> On 06/01/2022 08:05, Tony Lu wrote: >> >> I think of the following approach: the default maximum of active workers in a >> work queue is defined by WQ_MAX_ACTIVE (512). when this limit is hit then we >> have slightly lesser than 512 parallel SMC handshakes running at the moment, >> and new workers would be enqueued without to become active. >> In that case (max active workers reached) I would tend to fallback new connections >> to TCP. We would end up with lesser connections using SMC, but for the user space >> applications there would be nearly no change compared to TCP (no dropped TCP connection >> attempts, no need to reconnect). >> Imho, most users will never run into this problem, so I think its fine to behave like this. > > This makes sense to me, thanks. > >> >> As far as I understand you, you still see a good reason in having another behavior >> implemented in parallel (controllable by user) which enqueues all incoming connections >> like in your patch proposal? But how to deal with the out-of-memory problems that might >> happen with that? > > There is a possible scene, when the user only wants to use SMC protocol, such > as performance benchmark, or explicitly specify SMC protocol, they can > afford the lower speed of incoming connection creation, but enjoy the > higher QPS after creation. > >> Lets decide that when you have a specific control that you want to implement. >> I want to have a very good to introduce another interface into the SMC module, >> making the code more complex and all of that. The decision for the netlink interface >> was also done because we have the impression that this is the NEW way to go, and >> since we had no interface before we started with the most modern way to implement it. >> >> TCP et al have a history with sysfs, so thats why it is still there. >> But I might be wrong on that... > > Thanks for the information that I don't know about the decision for new > control interface. I am understanding your decision about the interface. > We are glad to contribute the knobs to smc_netlink.c in the next patches. > > There is something I want to discuss here about the persistent > configuration, we need to store new config in system, and make sure that > it could be loaded correctly after boot up. A possible solution is to > extend smc-tools for new config, and work with systemd for auto-loading. > If it works, we are glad to contribute these to smc-tools. I'd be definitely open to look into patches for smc-tools that extend it to configure SMC properties, and that provide the capability to read (and apply) a config from a file! We can discuss what you'd imagine as an interface before you implement it, too. Ciao, Stefan