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Date: Wed, 31 Aug 2022 17:04:10 +0200
From: Jan Karcher <jaka@...ux.ibm.com>
To: "D. Wythe" <alibuda@...ux.alibaba.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 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
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.
[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
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
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