On 09.11.22 10:10, D. Wythe wrote:
Hi Wenjia and Jan,I'm not sure whether my guess is right, I need some help from you. I guess the smcd_ops register_dmb() is not thread-safe, after I remove the lock, different connections might get the same sba_idx, which will cause the connection to be lost in the map(smcd->conn). If so, the CDC message carrying close/abort information cannot be distributed to the correct connection, then the connection remains in link group abnormally./* Set a connection using this DMBE. */ void smc_ism_set_conn(struct smc_connection *conn) { unsigned long flags; spin_lock_irqsave(&conn->lgr->smcd->lock, flags); conn->lgr->smcd->conn[conn->rmb_desc->sba_idx] = conn; spin_unlock_irqrestore(&conn->lgr->smcd->lock, flags); } struct smcd_ops { int (*register_dmb)(struct smcd_dev *dev, struct smcd_dmb *dmb); }
Hi D. Wythe,Very glad if we can help. It does look very questionable. However, I don't really think it's the reason to trigger the problem. I did some traces, and saw there was already something wrong during the CLC handshake, where one connection is decided for SMC-R not -D. This is one piece of the snapshot of the trace:
<...>-540539 [000] 306429.068196::| smc_connect() {
<...>-540539 [000] 306429.068198::| smc_copy_sock_settings_to_clc();
<...>-540539 [000] 306429.120310::| smc_ism_is_v2_capable();
<...>-540539 [000] 306429.120316::| .LASANPC6743();
<...>-540539 [000] 306429.120319::| smc_find_proposal_devices() {
<...>-540539 [000] 306429.120319::| smc_pnet_find_ism_resource() {
<...>-540539 [000] 306429.120331::| smc_pnet_match();
<...>-540539 [000] 306429.120332::| }
<...>-540539 [000] 306429.120333::| smc_ism_get_chid();
<...>-540539 [000] 306429.120334::| smc_pnet_find_roce_resource() {
<...>-540539 [000] 306429.120344::| smc_pnet_match();
<...>-540539 [000] 306429.120346::| smc_ib_port_active();
<...>-540539 [000] 306429.120347::| smc_pnet_determine_gid() {
<...>-540539 [000] 306429.120347::| smc_ib_determine_gid() {
<...>-540539 [000] 306429.120350::| smc_ib_determine_gid_rcu();
<...>-540539 [000] 306429.120351::| }
<...>-540539 [000] 306429.120352::| }
<...>-540539 [000] 306429.120352::| }
<...>-540539 [000] 306429.120353::| smc_ism_is_v2_capable();
<...>-540539 [000] 306429.120355::| smc_clc_ueid_count();
<...>-540539 [000] 306429.120357::| smc_pnet_find_roce_resource() {
<...>-540539 [000] 306429.120367::| smc_pnet_match();
<...>-540539 [000] 306429.120368::| smc_ib_port_active();
<...>-540539 [000] 306429.120369::| smc_pnet_determine_gid() {
<...>-540539 [000] 306429.120370::| smc_ib_determine_gid() {
<...>-540539 [000] 306429.120372::| smc_ib_determine_gid_rcu();
<...>-540539 [000] 306429.120376::| smc_ib_determine_gid_rcu();
<...>-540539 [000] 306429.120379::| smc_ib_determine_gid_rcu();
<...>-540539 [000] 306429.120382::| smc_ib_determine_gid_rcu();
<...>-540539 [000] 306429.120650::| }
<...>-540539 [000] 306429.120651::| }
<...>-540539 [000] 306429.120652::| smc_pnet_match();
<...>-540539 [000] 306429.120653::| smc_ib_port_active();
<...>-540539 [000] 306429.120654::| smc_pnet_determine_gid() {
<...>-540539 [000] 306429.120654::| smc_ib_determine_gid() {
<...>-540539 [000] 306429.120657::| smc_ib_determine_gid_rcu();
<...>-540539 [000] 306429.120660::| smc_ib_determine_gid_rcu();
<...>-540539 [000] 306429.120829::| }
<...>-540539 [000] 306429.120829::| }
<...>-540539 [000] 306429.120830::| }
<...>-540539 [000] 306429.120831::| }
<...>-540539 [000] 306429.120836::| .LASANPC6660() {
<...>-540539 [000] 306429.120843::| .LASANPC6654() {
<...>-540539 [000] 306429.120847::| smc_clc_prfx_set4_rcu.isra.0();
<...>-540539 [000] 306429.120849::| }
<...>-540539 [000] 306429.120850::| smc_ism_get_chid();
<...>-540539 [000] 306429.120851::| smc_ism_get_system_eid();
<...>-540539 [000] 306429.120889::| }
<...>-540539 [000] 306429.120890::| .LASANPC6658() {
<...>-540539 [000] 306429.124906::| smc_clc_msg_hdr_valid();
<...>-540539 [000] 306429.124908::| }
<...>-540539 [000] 306429.124908::| .LASANPC6727() {
<...>-540539 [000] 306429.124909::| smc_connect_rdma_v2_prepare();
<...>-540539 [000] 306429.124912::| smc_conn_create() {
On 11/7/22 7:05 PM, D. Wythe wrote:Hi Wenjia,Thanks a lot for your information, before that we thought you did PATCH test one by one, now I think I have found the root cause, and I will release a new version to fix thissoon as possible. Best Wishes. D. Wythe On 11/2/22 9:55 PM, Wenjia Zhang wrote:On 01.11.22 08:22, D. Wythe wrote:Hi Jan,Our team conducted some code reviews over this, but unfortunately no obvious problems were found. Hence we are waiting for Tony Lu's virtual SMC-D device to test, which is expected to come in this week. Before that, I wonder if your tests are running separately on separate PATCH? If so, I would like to please you to test the first PATCH and the second PATCH together. I doubt that the problem repaired by the second PATCHis the cause of this issues. Best Wishes. D. WytheHi D. Wythe,We did test the series of the patches as a whole. That would be great if you could use Tony's virtual device to test SMC-D. By the way, I'll put your patches in our CI, let's see if it can find something.Best, WenjiaOn 10/24/22 9:11 PM, Jan Karcher wrote:Hi D. Wythe, I re-run the tests with your fix.SMC-R works fine now. For SMC-D we still have the following problem. It is kind of the same as i reported in v2 but even weirder:smc stats: t8345011 SMC-D Connections Summary Total connections handled 2465 SMC-R Connections Summary Total connections handled 232 t8345010 SMC-D Connections Summary Total connections handled 2290 SMC-R Connections Summary Total connections handled 231 smc linkgroups: t8345011 [root@t8345011 ~]# smcr linkgroup LG-ID LG-Role LG-Type VLAN #Conns PNET-ID 00000400 SERV SYM 0 0 NET25 [root@t8345011 ~]# smcd linkgroup LG-ID VLAN #Conns PNET-ID 00000300 0 16 NET25 t8345010 [root@t8345010 tela-kernel]# smcr linkgroup LG-ID LG-Role LG-Type VLAN #Conns PNET-ID 00000400 CLNT SYM 0 0 NET25 [root@t8345010 tela-kernel]# smcd linkgroup LG-ID VLAN #Conns PNET-ID 00000300 0 1 NET25 smcss: t8345011 [root@t8345011 ~]# smcssState UID Inode Local Address Peer Address Intf Modet8345010 [root@t8345010 tela-kernel]# smcssState UID Inode Local Address Peer Address Intf Modelsmod: t8345011 [root@t8345011 ~]# lsmod | grep smc smc 225280 18 ism,smc_diag t8345010 [root@t8345010 tela-kernel]# lsmod | grep smc smc 225280 3 ism,smc_diagAlso smc_dbg and netstat do not show any more information on this problem. We only see in the dmesg that the code seems to build up SMC-R linkgroups even tho we are running the SMC-D tests.NOTE: we disabled the syncookies for the tests. dmesg: t8345011 smc-tests: test_smcapp_torture_test startedkernel: TCP: request_sock_TCP: Possible SYN flooding on port 22465. Dropping request. Check SNMP counters. kernel: smc: SMC-R lg 00000400 net 1 link added: id 00000401, peerid 00000401, ibdev mlx5_0, ibport 1 kernel: smc: SMC-R lg 00000400 net 1 state changed: SINGLE, pnetid NET25 kernel: smc: SMC-R lg 00000400 net 1 link added: id 00000402, peerid 00000402, ibdev mlx5_1, ibport 1 kernel: smc: SMC-R lg 00000400 net 1 state changed: SYMMETRIC, pnetid NET25t8345010 smc-tests: test_smcapp_torture_test startedkernel: smc: SMC-R lg 00000400 net 1 link added: id 00000401, peerid 00000401, ibdev mlx5_0, ibport 1 kernel: smc: SMC-R lg 00000400 net 1 state changed: SINGLE, pnetid NET25 kernel: smc: SMC-R lg 00000400 net 1 link added: id 00000402, peerid 00000402, ibdev mlx5_1, ibport 1 kernel: smc: SMC-R lg 00000400 net 1 state changed: SYMMETRIC, pnetid NET25If this output does not help and if you want us to look deeper into it feel free to let us know and we can debug further.On 23/10/2022 14:43, D.Wythe wrote:From: "D.Wythe" <alibuda@xxxxxxxxxxxxxxxxx>This patch set attempts to optimize the parallelism of SMC-R connections, mainly to reduce unnecessary blocking on locks, and to fix exceptions thatoccur 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 wherenetwork 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 relevantoptimization patches as soon as possible. Please note that the premise here is that the lock related problemmust 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. Only wake up one connection if the lnk is not active 4. Delete obsolete unlock logic in smc_listen_work() 5. PATCH format, do Reverse Christmas tree 6. PATCH format, change all xxx_lnk_xxx function to xxx_link_xxx 7. PATCH format, add correct fix tag for the patches for fixes. 8. PATCH format, fix some spelling error 9. PATCH format, rename slow to do_slow v2 -> v3:1. add SMC-D support, remove the concept of link cluster since SMC-D has no link at all. Replace it by lgr decision maker, who provides suggestionsto SMC-D and SMC-R on whether to create new link group. 2. Fix the corruption problem described by PATCH 'fix application data exception' on SMC-D. v3 -> v4: 1. Fix panic caused by uninitialization map. D. Wythe (10): net/smc: remove locks smc_client_lgr_pending and smc_server_lgr_pendingnet/smc: fix SMC_CLC_DECL_ERR_REGRMB without smc_server_lgr_pendingnet/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_semaphorenet/smc: Fix potential panic dues to unprotected smc_llc_srv_add_link() net/smc: fix application data exception net/smc/af_smc.c | 70 ++++----net/smc/smc_core.c | 478 +++++++++++++++++++++++++++++++++++++++++++++++------net/smc/smc_core.h | 36 +++- net/smc/smc_llc.c | 277 ++++++++++++++++++++++--------- net/smc/smc_llc.h | 6 + net/smc/smc_wr.c | 10 -- net/smc/smc_wr.h | 10 ++ 7 files changed, 712 insertions(+), 175 deletions(-)
