From patchwork Fri Aug 26 09:51:27 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "D. Wythe" X-Patchwork-Id: 12955794 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 899AFECAAA3 for ; Fri, 26 Aug 2022 09:51:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230052AbiHZJvz (ORCPT ); Fri, 26 Aug 2022 05:51:55 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56518 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S241772AbiHZJvx (ORCPT ); Fri, 26 Aug 2022 05:51:53 -0400 Received: from out30-42.freemail.mail.aliyun.com (out30-42.freemail.mail.aliyun.com [115.124.30.42]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E5C38D758A; Fri, 26 Aug 2022 02:51:50 -0700 (PDT) X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R111e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=ay29a033018046056;MF=alibuda@linux.alibaba.com;NM=1;PH=DS;RN=8;SR=0;TI=SMTPD_---0VNIZezx_1661507507; Received: from localhost(mailfrom:alibuda@linux.alibaba.com fp:SMTPD_---0VNIZezx_1661507507) by smtp.aliyun-inc.com; Fri, 26 Aug 2022 17:51:48 +0800 From: "D. Wythe" To: kgraul@linux.ibm.com, wenjia@linux.ibm.com Cc: kuba@kernel.org, davem@davemloft.net, netdev@vger.kernel.org, linux-s390@vger.kernel.org, linux-rdma@vger.kernel.org, "D. Wythe" Subject: [PATCH net-next v2 00/10] optimize the parallelism of SMC-R connections Date: Fri, 26 Aug 2022 17:51:27 +0800 Message-Id: X-Mailer: git-send-email 1.8.3.1 Precedence: bulk List-ID: X-Mailing-List: linux-rdma@vger.kernel.org From: "D. Wythe" This patch set attempts to optimize the parallelism of SMC-R connections, mainly to reduce unnecessary blocking on locks, and to fix exceptions that occur after thoses optimization. According to Off-CPU graph, SMC worker's off-CPU as that: smc_close_passive_work (1.09%) smcr_buf_unuse (1.08%) smc_llc_flow_initiate (1.02%) smc_listen_work (48.17%) __mutex_lock.isra.11 (47.96%) An ideal SMC-R connection process should only block on the IO events of the network, but it's quite clear that the SMC-R connection now is queued on the lock most of the time. The goal of this patchset is to achieve our ideal situation where network IO events are blocked for the majority of the connection lifetime. There are three big locks here: 1. smc_client_lgr_pending & smc_server_lgr_pending 2. llc_conf_mutex 3. rmbs_lock & sndbufs_lock And an implementation issue: 1. confirm/delete rkey msg can't be sent concurrently while protocol allows indeed. Unfortunately,The above problems together affect the parallelism of SMC-R connection. If any of them are not solved. our goal cannot be achieved. After this patch set, we can get a quite ideal off-CPU graph as following: smc_close_passive_work (41.58%) smcr_buf_unuse (41.57%) smc_llc_do_delete_rkey (41.57%) smc_listen_work (39.10%) smc_clc_wait_msg (13.18%) tcp_recvmsg_locked (13.18) smc_listen_find_device (25.87%) smcr_lgr_reg_rmbs (25.87%) smc_llc_do_confirm_rkey (25.87%) We can see that most of the waiting times are waiting for network IO events. This also has a certain performance improvement on our short-lived conenction wrk/nginx benchmark test: +--------------+------+------+-------+--------+------+--------+ |conns/qps |c4 | c8 | c16 | c32 | c64 | c200 | +--------------+------+------+-------+--------+------+--------+ |SMC-R before |9.7k | 10k | 10k | 9.9k | 9.1k | 8.9k | +--------------+------+------+-------+--------+------+--------+ |SMC-R now |13k | 19k | 18k | 16k | 15k | 12k | +--------------+------+------+-------+--------+------+--------+ |TCP |15k | 35k | 51k | 80k | 100k | 162k | +--------------+------+------+-------+--------+------+--------+ The reason why the benefit is not obvious after the number of connections has increased dues to workqueue. If we try to change workqueue to UNBOUND, we can obtain at least 4-5 times performance improvement, reach up to half of TCP. However, this is not an elegant solution, the optimization of it will be much more complicated. But in any case, we will submit relevant optimization patches as soon as possible. Please note that the premise here is that the lock related problem must be solved first, otherwise, no matter how we optimize the workqueue, there won't be much improvement. Because there are a lot of related changes to the code, if you have any questions or suggestions, please let me know. Thanks D. Wythe v1 -> v2: 1. Fix panic in SMC-D scenario 2. Fix lnkc related hashfn calculation exception, caused by operator priority. 3. Remove -EBUSY processing of rhashtable_insert_fast, see more details in comments around smcr_link_get_or_create_cluster(). 4. Only wake up one connection if the link has not been active. 5. Delete obsolete unlock logic in smc_listen_work(). 6. PATCH format, do Reverse Christmas tree. 7. PATCH format, change all xxx_lnk_xxx function to xxx_link_xxx. 8. PATCH format, add correct fix tag for the patches for fixes. 9. PATCH format, fix some spelling error. 10.PATCH format, rename slow to do_slow in smcr_lgr_reg_rmbs(). D. Wythe (10): net/smc: remove locks smc_client_lgr_pending and smc_server_lgr_pending net/smc: fix SMC_CLC_DECL_ERR_REGRMB without smc_server_lgr_pending net/smc: allow confirm/delete rkey response deliver multiplex net/smc: make SMC_LLC_FLOW_RKEY run concurrently net/smc: llc_conf_mutex refactor, replace it with rw_semaphore net/smc: use read semaphores to reduce unnecessary blocking in smc_buf_create() & smcr_buf_unuse() net/smc: reduce unnecessary blocking in smcr_lgr_reg_rmbs() net/smc: replace mutex rmbs_lock and sndbufs_lock with rw_semaphore net/smc: Fix potential panic dues to unprotected smc_llc_srv_add_link() net/smc: fix application data exception net/smc/af_smc.c | 42 +++-- net/smc/smc_core.c | 443 +++++++++++++++++++++++++++++++++++++++++++++++------ net/smc/smc_core.h | 78 +++++++++- net/smc/smc_llc.c | 286 +++++++++++++++++++++++++--------- net/smc/smc_llc.h | 6 + net/smc/smc_wr.c | 10 -- net/smc/smc_wr.h | 10 ++ 7 files changed, 725 insertions(+), 150 deletions(-)