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Message-ID: <377011d2-7f9d-bf7f-8366-c579bf42c396@linux.alibaba.com>
Date: Fri, 2 Sep 2022 19:25:50 +0800
From: "D. Wythe" <alibuda@...ux.alibaba.com>
To: Jan Karcher <jaka@...ux.ibm.com>, kgraul@...ux.ibm.com,
wenjia@...ux.ibm.com
Cc: kuba@...nel.org, davem@...emloft.net, netdev@...r.kernel.org,
linux-s390@...r.kernel.org, linux-rdma@...r.kernel.org
Subject: Re: [PATCH net-next v2 01/10] net/smc: remove locks
smc_client_lgr_pending and smc_server_lgr_pending
On 8/31/22 11:04 PM, Jan Karcher wrote:
>
>
> On 26.08.2022 11:51, D. Wythe wrote:
>> From: "D. Wythe" <alibuda@...ux.alibaba.com>
>>
>> This patch attempts to remove locks named smc_client_lgr_pending and
>> smc_server_lgr_pending, which aim to serialize the creation of link
>> group. However, once link group existed already, those locks are
>> meaningless, worse still, they make incoming connections have to be
>> queued one after the other.
>>
>> Now, the creation of link group is no longer generated by competition,
>> but allocated through following strategy.
>>
>> 1. Try to find a suitable link group, if successd, current connection
>> is considered as NON first contact connection. ends.
>>
>> 2. Check the number of connections currently waiting for a suitable
>> link group to be created, if it is not less that the number of link
>> groups to be created multiplied by (SMC_RMBS_PER_LGR_MAX - 1), then
>> increase the number of link groups to be created, current connection
>> is considered as the first contact connection. ends.
>>
>> 3. Increase the number of connections currently waiting, and wait
>> for woken up.
>>
>> 4. Decrease the number of connections currently waiting, goto 1.
>>
>> We wake up the connection that was put to sleep in stage 3 through
>> the SMC link state change event. Once the link moves out of the
>> SMC_LNK_ACTIVATING state, decrease the number of link groups to
>> be created, and then wake up at most (SMC_RMBS_PER_LGR_MAX - 1)
>> connections.
>>
>> In the iplementation, we introduce the concept of lnk cluster, which is
>> a collection of links with the same characteristics (see
>> smcr_lnk_cluster_cmpfn() with more details), which makes it possible to
>> wake up efficiently in the scenario of N v.s 1.
>>
>> Signed-off-by: D. Wythe <alibuda@...ux.alibaba.com>
>
> Hello D.,
>
> thanks for the v2 and the patience.
> I got to testing and as with v1 I want to share our findings with you. If you need more information or want us to look deeper into the findings please let us know.
>
> Regarding SMC-R test-suite:
> We see a refcount error during one of our stress tests. This lets us believe that the smc_link_cluster_put() to smc_link_cluster_hold() ratio is not right anymore.
> The patch provided by yacan does fix this issue but we did not verify if it is the right way to balance the hold and put calls.
>
> [root@...45011 ~]# journalctl --dmesg | tail -100
> Aug 31 16:17:36 t8345011.lnxne.boe smc-tests: test_smcapp_50x_ifdown started
> Aug 31 16:17:46 t8345011.lnxne.boe kernel: smc: SMC-R lg 00000100 net 1 link removed: id 00000101, peerid 00000101, ibdev mlx5_0, ibport 1
> Aug 31 16:17:46 t8345011.lnxne.boe kernel: smc: SMC-R lg 00000100 net 1 state changed: SINGLE, pnetid NET25
> Aug 31 16:17:46 t8345011.lnxne.boe kernel: smc: SMC-R lg 00000100 net 1 link added: id 00000103, peerid 00000103, ibdev mlx5_0, ibport 1
> Aug 31 16:17:46 t8345011.lnxne.boe kernel: smc: SMC-R lg 00000100 net 1 state changed: ASYMMETRIC_PEER, pnetid NET25
> Aug 31 16:17:55 t8345011.lnxne.boe kernel: smc: SMC-R lg 00000100 net 1 link added: id 00000104, peerid 00000104, ibdev mlx5_0, ibport 1
> Aug 31 16:17:55 t8345011.lnxne.boe kernel: smc: SMC-R lg 00000100 net 1 state changed: SYMMETRIC, pnetid NET25
> Aug 31 16:17:55 t8345011.lnxne.boe kernel: ------------[ cut here ]------------
> Aug 31 16:17:55 t8345011.lnxne.boe kernel: refcount_t: underflow; use-after-free.
> Aug 31 16:17:55 t8345011.lnxne.boe kernel: WARNING: CPU: 1 PID: 150 at lib/refcount.c:87 refcount_dec_not_one+0x88/0xa8
> Aug 31 16:17:55 t8345011.lnxne.boe kernel: Modules linked in: smc_diag tcp_diag inet_diag nft_fib_inet nft_fib_ipv4 nft_fib_ipv6 nft_fib nft_reject_inet nf_reject_ipv4 nf_reject_ipv6 nft_reject nft_ct nft_chain_nat nf_nat nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 ip_set nf_tables nfnetlink mlx5_ib ism smc ib_uverbs ib_core vfio_ccw mdev s390_trng vfio_iommu_type1 vfio sch_fq_codel configfs ip_tables x_tables ghash_s390 prng chacha_s390 libchacha aes_s390 mlx5_core des_s390 libdes sha3_512_s390 sha3_256_s390 sha512_s390 sha256_s390 sha1_s390 sha_common pkey zcrypt rng_core autofs4
> Aug 31 16:17:55 t8345011.lnxne.boe kernel: CPU: 1 PID: 150 Comm: kworker/1:2 Not tainted 6.0.0-rc2-00493-g91ecd751199f #8
> Aug 31 16:17:55 t8345011.lnxne.boe kernel: Hardware name: IBM 8561 T01 701 (z/VM 7.2.0)
> Aug 31 16:17:55 t8345011.lnxne.boe kernel: Workqueue: events smc_llc_add_link_work [smc]
> Aug 31 16:17:55 t8345011.lnxne.boe kernel: Krnl PSW : 0704c00180000000 000000005b31f32c (refcount_dec_not_one+0x8c/0xa8)
> Aug 31 16:17:55 t8345011.lnxne.boe kernel: R:0 T:1 IO:1 EX:1 Key:0 M:1 W:0 P:0 AS:3 CC:0 PM:0 RI:0 EA:3
> Aug 31 16:17:55 t8345011.lnxne.boe kernel: Krnl GPRS: 00000000ffffffea 0000000000000027 0000000000000026 000000005c3151e0
> Aug 31 16:17:55 t8345011.lnxne.boe kernel: 00000000fee80000 0000038000000001 000000008e0e9a00 000000008de79c24
> Aug 31 16:17:55 t8345011.lnxne.boe kernel: 0000038000000000 000003ff803f05ac 0000000095038360 000000008de79c00
> Aug 31 16:17:55 t8345011.lnxne.boe kernel: 00000000828ca100 0000000095038360 000000005b31f328 0000038000943b50
> Aug 31 16:17:55 t8345011.lnxne.boe kernel: Krnl Code: 000000005b31f31c: c02000466122 larl %r2,000000005bbeb560
> 000000005b31f322: c0e500232e53 brasl %r14,000000005b784fc8
> #000000005b31f328: af000000 mc 0,0
> >000000005b31f32c: a7280001 lhi %r2,1
> 000000005b31f330: ebeff0a00004 lmg %r14,%r15,160(%r15)
> 000000005b31f336: ec223fbf0055 risbg %r2,%r2,63,191,0
> 000000005b31f33c: 07fe bcr 15,%r14
> 000000005b31f33e: 47000700 bc 0,1792
> Aug 31 16:17:55 t8345011.lnxne.boe kernel: Call Trace:
> Aug 31 16:17:55 t8345011.lnxne.boe kernel: [<000000005b31f32c>] refcount_dec_not_one+0x8c/0xa8
> Aug 31 16:17:55 t8345011.lnxne.boe kernel: ([<000000005b31f328>] refcount_dec_not_one+0x88/0xa8)
> Aug 31 16:17:55 t8345011.lnxne.boe kernel: [<000003ff803ef16a>] smcr_link_cluster_on_link_state.part.0+0x1ba/0x440 [smc]
> Aug 31 16:17:55 t8345011.lnxne.boe kernel: [<000003ff803f05ac>] smcr_link_clear+0x5c/0x1b0 [smc]
> Aug 31 16:17:55 t8345011.lnxne.boe kernel: [<000003ff803fadf4>] smc_llc_add_link_work+0x43c/0x470 [smc]
> Aug 31 16:17:55 t8345011.lnxne.boe kernel: [<000000005ac1f0e2>] process_one_work+0x1fa/0x478
> Aug 31 16:17:55 t8345011.lnxne.boe kernel: [<000000005ac1f88c>] worker_thread+0x64/0x468
> Aug 31 16:17:55 t8345011.lnxne.boe kernel: [<000000005ac28580>] kthread+0x108/0x110
> Aug 31 16:17:55 t8345011.lnxne.boe kernel: [<000000005abaf2dc>] __ret_from_fork+0x3c/0x58
> Aug 31 16:17:55 t8345011.lnxne.boe kernel: [<000000005b7a4d6a>] ret_from_fork+0xa/0x40
> Aug 31 16:17:55 t8345011.lnxne.boe kernel: Last Breaking-Event-Address:
> Aug 31 16:17:55 t8345011.lnxne.boe kernel: [<000000005b785028>] __warn_printk+0x60/0x68
Thank you for your test, I need to think about it, please give me some time.
> Aug 31 16:17:55 t8345011.lnxne.boe kernel: ---[ end trace 0000000000000000 ]---
> Aug 31 16:17:55 t8345011.lnxne.boe kernel: smc: SMC-R lg 00000100 net 1 link removed: id 00000103, peerid 00000103, ibdev mlx5_0, ibport 1
> [root@...45011 ~]#
>
>
>
> Regarding SMC-D test-suite:
> For SMC-D we also see errors during another stress test. While we expect connections to fall back to TCP due to the limit of parallel connections your patch introduces TCP fallbacks with a new reason.
>
> [root@...45011 ~]# journalctl --dmesg | tail -10
> Aug 31 16:30:07 t8345011.lnxne.boe smc-tests: test_oob7_send_multi_urg_at_start started
> Aug 31 16:30:16 t8345011.lnxne.boe smc-tests: test_oob8_ignore_some_urg_data started
> Aug 31 16:30:30 t8345011.lnxne.boe smc-tests: test_smc_tool_second started
> Aug 31 16:30:34 t8345011.lnxne.boe smc-tests: test_tshark started
> Aug 31 16:30:34 t8345011.lnxne.boe smc-tests: test_smcapp_torture_test started
> Aug 31 16:30:49 t8345011.lnxne.boe kernel: smc: SMC-R lg 00000400 net 1 link added: id 00000401, peerid 00000401, ibdev mlx5_0, ibport 1
> Aug 31 16:30:49 t8345011.lnxne.boe kernel: smc: SMC-R lg 00000400 net 1 state changed: SINGLE, pnetid NET25
> Aug 31 16:30:49 t8345011.lnxne.boe kernel: TCP: request_sock_TCP: Possible SYN flooding on port 51897. Sending cookies. Check SNMP counters.
> Aug 31 16:30:49 t8345011.lnxne.boe kernel: smc: SMC-R lg 00000400 net 1 link added: id 00000402, peerid 00000402, ibdev mlx5_1, ibport 1
> Aug 31 16:30:49 t8345011.lnxne.boe kernel: smc: SMC-R lg 00000400 net 1 state changed: SYMMETRIC, pnetid NET25
>
> ^
> I am wondering why we see SMC-R dmesgs even if we communicate with SMC-D. Gotta verify that. Can be an error on our side.
This is very weird, is there no such SMC-R dmesgs before apply my PATCH?
I am not sure if there is logic to downgrade SMC-D to SMC-R, maybe it's has related to 0x03010000.
I need to check the code, the reason will be sent out as soon as possible
> [root@...45011 ~]#
> [root@...45011 ~]# smcss
> ACTIVE 00000 0067005 10.25.45.10:48096 10.25.45.11:51897 0000 SMCD
> ACTIVE 00000 0067001 10.25.45.10:48060 10.25.45.11:51897 0000 SMCD
> ACTIVE 00000 0066999 10.25.45.10:48054 10.25.45.11:51897 0000 SMCD
> ACTIVE 00000 0068762 10.25.45.10:48046 10.25.45.11:51897 0000 SMCD
> ACTIVE 00000 0066997 10.25.45.10:48044 10.25.45.11:51897 0000 SMCD
> ACTIVE 00000 0068760 10.25.45.10:48036 10.25.45.11:51897 0000 SMCD
> ACTIVE 00000 0066995 10.25.45.10:48026 10.25.45.11:51897 0000 SMCD
> ACTIVE 00000 0068758 10.25.45.10:48024 10.25.45.11:51897 0000 SMCD
> ACTIVE 00000 0066993 10.25.45.10:48022 10.25.45.11:51897 0000 SMCD
> ACTIVE 00000 0068756 10.25.45.10:48006 10.25.45.11:51897 0000 SMCD
> ACTIVE 00000 0066991 10.25.45.10:47998 10.25.45.11:51897 0000 SMCD
> ACTIVE 00000 0068754 10.25.45.10:47984 10.25.45.11:51897 0000 SMCD
> ACTIVE 00000 0067124 10.25.45.11:51897 10.25.45.10:48314 0000 TCP 0x05000000/0x030d0000
> ACTIVE 00000 0067121 10.25.45.11:51897 10.25.45.10:48302 0000 TCP 0x05000000/0x030d0000
> ACTIVE 00000 0067120 10.25.45.11:51897 10.25.45.10:48284 0000 TCP 0x05000000/0x030d0000
> ACTIVE 00000 0067114 10.25.45.11:51897 10.25.45.10:48282 0000 TCP 0x05000000/0x030d0000
> ACTIVE 00000 0067115 10.25.45.11:51897 10.25.45.10:48254 0000 TCP 0x05000000/0x030d0000
> ACTIVE 00000 0067111 10.25.45.11:51897 10.25.45.10:48250 0000 TCP 0x05000000/0x030d0000
> ACTIVE 00000 0066415 10.25.45.11:51897 10.25.45.10:48242 0000 TCP 0x05000000/0x030d0000
> ACTIVE 00000 0067113 10.25.45.11:51897 10.25.45.10:48230 0000 TCP 0x05000000/0x030d0000
> ACTIVE 00000 0066409 10.25.45.11:51897 10.25.45.10:48202 0000 TCP 0x05000000/0x030d0000
> ACTIVE 00000 0066413 10.25.45.11:51897 10.25.45.10:48214 0000 TCP 0x05000000/0x030d0000
> ACTIVE 00000 0066414 10.25.45.11:51897 10.25.45.10:48204 0000 TCP 0x05000000/0x030d0000
> ACTIVE 00000 0066397 10.25.45.11:51897 10.25.45.10:48120 0000 TCP 0x05000000/0x030d0000
> ACTIVE 00000 0066399 10.25.45.11:51897 10.25.45.10:48084 0000 TCP 0x05000000/0x030d0000
> ACTIVE 00000 0066396 10.25.45.11:51897 10.25.45.10:48078 0000 TCP 0x05000000/0x030d0000
> ACTIVE 00000 0062632 10.25.45.11:51897 10.25.45.10:43120 0000 TCP 0x03010000
> ACTIVE 00000 0062631 10.25.45.11:51897 10.25.45.10:43134 0000 TCP 0x03010000
> ACTIVE 00000 0062626 10.25.45.11:51897 10.25.45.10:43106 0000 TCP 0x03010000
> ACTIVE 00000 0062625 10.25.45.11:51897 10.25.45.10:43138 0000 TCP 0x03010000
> ACTIVE 00000 0062621 10.25.45.11:51897 10.25.45.10:43160 0000 TCP 0x03010000
> ACTIVE 00000 0061580 10.25.45.11:51897 10.25.45.10:42820 0000 TCP 0x03010000
> ACTIVE 00000 0061558 10.25.45.11:51897 10.25.45.10:42792 0000 TCP 0x03010000
> ACTIVE 00000 0061549 10.25.45.11:51897 10.25.45.10:42816 0000 TCP 0x03010000
> ACTIVE 00000 0061548 10.25.45.11:51897 10.25.45.10:42764 0000 TCP 0x03010000
> ACTIVE 00000 0061544 10.25.45.11:51897 10.25.45.10:42804 0000 TCP 0x03010000
> ACTIVE 00000 0061543 10.25.45.11:51897 10.25.45.10:42856 0000 TCP 0x03010000
> ACTIVE 00000 0061542 10.25.45.11:51897 10.25.45.10:42756 0000 TCP 0x03010000
> ACTIVE 00000 0062554 10.25.45.11:51897 10.25.45.10:42852 0000 TCP 0x03010000
> ACTIVE 00000 0062553 10.25.45.11:51897 10.25.45.10:42844 0000 TCP 0x03010000
> ACTIVE 00000 0062549 10.25.45.11:51897 10.25.45.10:42836 0000 TCP 0x03010000
>
> ^
> Here SMCD and 0x05000000/0x030d0000 are expected. But:
> [353] smcss confirmed connection of type SMCD
> [353] Error: Found TCP fallback due to unexpected reasons: 0x03010000
sysctl -w net.ipv4.tcp_syncookies=0
Can you retry your test after set above configure? When TCP detects a potential flooding attack,
it will starts syn-cookies to verify traffic. In this case, SMC can't work, and then triggering a fallback with
error code 0x03010000.
This doesn't seem to be the problem that my PATCH can cause, but my PATCH removes the lock in
the handshake phase, which may speed up the frequency of your test initiating connections,
But I can't be sure ...
> We also exeperience that the lsmod count stays above 2 even after the testcase finished and takes quite a while before it goes down again (we send a kill signal at the end of our testcase).
>
> During test (which is fine)
>
> [root@...45011 ~]# lsmod | grep smc
> smc_diag 16384 0
> smc 225280 2981 ism,smc_diag
> ib_core 413696 3 smc,ib_uverbs,mlx5_ib
>
> Count > 2 even after tests finish!
>
> [root@...45011 ~]# lsmod | grep smc
> smc_diag 16384 0
> smc 225280 40 ism,smc_diag
> ib_core 413696 3 smc,ib_uverbs,mlx5_ib
> Let us know if you need any more information.
> Thanks, Jan
This usually means that there are still connections that are not really destroyed,
can you try this and to see if there are any remaining connections?
smcd linkgroup; #or smcr, it depends, if any, can you show us the connection state (smcss -r or -d)
ps aux | grep D; # check if there is work thread hungs, if any, please show us the /proc/$PID/stack.
D. Wythe
Thanks.
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