| Message ID | cover.1660152975.git.alibuda@linux.alibaba.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | net/smc: optimize the parallelism of SMC-R connections | expand |
On Thu, 11 Aug 2022 01:47:31 +0800 D. Wythe wrote: > From: "D. Wythe" <alibuda@linux.alibaba.com> > > 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. net-next is closed until Monday, please see the FAQ. Also Al Viro complained about the SMC ULP: https://lore.kernel.org/all/YutBc9aCQOvPPlWN@ZenIV/ I didn't see any responses, what the situation there?
On Wed, Aug 10, 2022 at 08:28:45PM -0700, Jakub Kicinski wrote: > On Thu, 11 Aug 2022 01:47:31 +0800 D. Wythe wrote: > > From: "D. Wythe" <alibuda@linux.alibaba.com> > > > > 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. > > net-next is closed until Monday, please see the FAQ. > > Also Al Viro complained about the SMC ULP: > > https://lore.kernel.org/all/YutBc9aCQOvPPlWN@ZenIV/ > > I didn't see any responses, what the situation there? Sorry for the late reply. I am working on it and will give out the details as soon as possible. Tony Lu
On 10/08/2022 19:47, D. Wythe wrote: > From: "D. Wythe" <alibuda@linux.alibaba.com> > > 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. This are very interesting changes. Please allow us to review and test on the s390 architecture. Thank you for this submission!
On 10.08.2022 19:47, D. Wythe wrote: > From: "D. Wythe" <alibuda@linux.alibaba.com> > > 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. > Thank you again for your submission! Let me give you a quick update from our side: We tested your patches on top of the net-next kernel on our s390 systems. They did crash our systems. After verifying our environment we pulled console logs and now we can tell that there is indeed a problem with your patches regarding SMC-D. So please do not integrate this change as of right now. I'm going to do more in depth reviews of your patches but i need some time for them so here is a quick a description of the problem: It is a SMC-D problem, that occurs while building up the connection. In smc_conn_create you set struct smc_lnk_cluster *lnkc = NULL. For the SMC-R path you do grab the pointer, for SMC-D that never happens. Still you are using this refernce for SMC-D => Crash. This problem can be reproduced using the SMC-D path. Here is an example console output: [ 779.516382] Unable to handle kernel pointer dereference in virtual kernel address space [ 779.516389] Failing address: 0000000000000000 TEID: 0000000000000483 [ 779.516391] Fault in home space mode while using kernel ASCE. [ 779.516395] AS:0000000069628007 R3:00000000ffbf0007 S:00000000ffbef800 P:000000000000003d [ 779.516431] Oops: 0004 ilc:2 [#1] SMP [ 779.516436] Modules linked in: tcp_diag inet_diag ism mlx5_ib ib_uverbs mlx5_core smc_diag smc ib_core 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_ipv 6 nf_defrag_ipv4 ip_set nf_tables n [ 779.516470] CPU: 0 PID: 24 Comm: kworker/0:1 Not tainted 5.19.0-13940-g22a46254655a #3 [ 779.516476] Hardware name: IBM 8561 T01 701 (z/VM 7.2.0) [ 779.522738] Workqueue: smc_hs_wq smc_listen_work [smc] [ 779.522755] Krnl PSW : 0704c00180000000 000003ff803da89c (smc_conn_create+0x174/0x968 [smc]) [ 779.522766] 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 [ 779.522770] Krnl GPRS: 0000000000000002 0000000000000000 0000000000000001 0000000000000000 [ 779.522773] 000000008a4128a0 000003ff803f21aa 000000008e30d640 0000000086d72000 [ 779.522776] 0000000086d72000 000000008a412803 000000008a412800 000000008e30d650 [ 779.522779] 0000000080934200 0000000000000000 000003ff803cb954 00000380002dfa88 [ 779.522789] Krnl Code: 000003ff803da88e: e310f0e80024 stg %r1,232(%r15) [ 779.522789] 000003ff803da894: a7180000 lhi %r1,0 [ 779.522789] #000003ff803da898: 582003ac l %r2,940 [ 779.522789] >000003ff803da89c: ba123020 cs %r1,%r2,32(%r3) [ 779.522789] 000003ff803da8a0: ec1603be007e cij %r1,0,6,000003ff803db01c [ 779.522789] 000003ff803da8a6: 4110b002 la %r1,2(%r11) [ 779.522789] 000003ff803da8aa: e310f0f00024 stg %r1,240(%r15) [ 779.522789] 000003ff803da8b0: e310f0c00004 lg %r1,192(%r15) [ 779.522870] Call Trace: [ 779.522873] [<000003ff803da89c>] smc_conn_create+0x174/0x968 [smc] [ 779.522884] [<000003ff803cb954>] smc_find_ism_v2_device_serv+0x1b4/0x300 [smc] 01: HCPGSP2629I The virtual machine is placed in CP mode due to a SIGP stop from CPU 01. 01: HCPGSP2629I The virtual machine is placed in CP mode due to a SIGP stop from CPU 00. [ 779.522894] [<000003ff803cbace>] smc_listen_find_device+0x2e/0x370 [smc] I'm going to send the review for the first patch right away (which is the one causing the crash), so far I'm done with it. The others are going to follow. Maybe you can look over the problem and come up with a solution, otherwise we are going to decide if we want to look into it as soon as I'm done with the reviews. Thank you for your patience.
On Tue, Aug 16, 2022 at 11:35:15AM +0200, Jan Karcher wrote: > > > On 10.08.2022 19:47, D. Wythe wrote: > > From: "D. Wythe" <alibuda@linux.alibaba.com> > > > > 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. > > > > Thank you again for your submission! > Let me give you a quick update from our side: > We tested your patches on top of the net-next kernel on our s390 systems. > They did crash our systems. After verifying our environment we pulled > console logs and now we can tell that there is indeed a problem with your > patches regarding SMC-D. So please do not integrate this change as of right > now. I'm going to do more in depth reviews of your patches but i need some > time for them so here is a quick a description of the problem: > > It is a SMC-D problem, that occurs while building up the connection. In > smc_conn_create you set struct smc_lnk_cluster *lnkc = NULL. For the SMC-R > path you do grab the pointer, for SMC-D that never happens. Still you are > using this refernce for SMC-D => Crash. This problem can be reproduced using > the SMC-D path. Here is an example console output: Got it. > > [ 779.516382] Unable to handle kernel pointer dereference in virtual kernel > address space > [ 779.516389] Failing address: 0000000000000000 TEID: 0000000000000483 > [ 779.516391] Fault in home space mode while using kernel ASCE. > [ 779.516395] AS:0000000069628007 R3:00000000ffbf0007 S:00000000ffbef800 > P:000000000000003d > [ 779.516431] Oops: 0004 ilc:2 [#1] SMP > [ 779.516436] Modules linked in: tcp_diag inet_diag ism mlx5_ib ib_uverbs > mlx5_core smc_diag smc ib_core 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_ipv > 6 nf_defrag_ipv4 ip_set nf_tables n > [ 779.516470] CPU: 0 PID: 24 Comm: kworker/0:1 Not tainted > 5.19.0-13940-g22a46254655a #3 > [ 779.516476] Hardware name: IBM 8561 T01 701 (z/VM 7.2.0) > > [ 779.522738] Workqueue: smc_hs_wq smc_listen_work [smc] > [ 779.522755] Krnl PSW : 0704c00180000000 000003ff803da89c > (smc_conn_create+0x174/0x968 [smc]) > [ 779.522766] 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 > [ 779.522770] Krnl GPRS: 0000000000000002 0000000000000000 0000000000000001 > 0000000000000000 > [ 779.522773] 000000008a4128a0 000003ff803f21aa 000000008e30d640 > 0000000086d72000 > [ 779.522776] 0000000086d72000 000000008a412803 000000008a412800 > 000000008e30d650 > [ 779.522779] 0000000080934200 0000000000000000 000003ff803cb954 > 00000380002dfa88 > [ 779.522789] Krnl Code: 000003ff803da88e: e310f0e80024 stg > %r1,232(%r15) > [ 779.522789] 000003ff803da894: a7180000 lhi %r1,0 > [ 779.522789] #000003ff803da898: 582003ac l %r2,940 > [ 779.522789] >000003ff803da89c: ba123020 cs > %r1,%r2,32(%r3) > [ 779.522789] 000003ff803da8a0: ec1603be007e cij > %r1,0,6,000003ff803db01c > > [ 779.522789] 000003ff803da8a6: 4110b002 la > %r1,2(%r11) > [ 779.522789] 000003ff803da8aa: e310f0f00024 stg > %r1,240(%r15) > [ 779.522789] 000003ff803da8b0: e310f0c00004 lg > %r1,192(%r15) > [ 779.522870] Call Trace: > [ 779.522873] [<000003ff803da89c>] smc_conn_create+0x174/0x968 [smc] > [ 779.522884] [<000003ff803cb954>] smc_find_ism_v2_device_serv+0x1b4/0x300 > [smc] > 01: HCPGSP2629I The virtual machine is placed in CP mode due to a SIGP stop > from CPU 01. > 01: HCPGSP2629I The virtual machine is placed in CP mode due to a SIGP stop > from CPU 00. > [ 779.522894] [<000003ff803cbace>] smc_listen_find_device+0x2e/0x370 [smc] > > > I'm going to send the review for the first patch right away (which is the > one causing the crash), so far I'm done with it. The others are going to > follow. Maybe you can look over the problem and come up with a solution, > otherwise we are going to decide if we want to look into it as soon as I'm > done with the reviews. Thank you for your patience. Thanks for pointing this issue. We will fix this soon in v2. Tony Lu
On 8/16/22 5:35 PM, Jan Karcher wrote: > > > On 10.08.2022 19:47, D. Wythe wrote: >> From: "D. Wythe" <alibuda@linux.alibaba.com> >> >> 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. >> > > Thank you again for your submission! > Let me give you a quick update from our side: > We tested your patches on top of the net-next kernel on our s390 systems. They did crash our systems. After verifying our environment we pulled console logs and now we can tell that there is indeed a problem with your patches regarding SMC-D. So please do not integrate this change as of right now. I'm going to do more in depth reviews of your patches but i need some time for them so here is a quick a description of the problem: Sorry for the late reply, and thanks a lot for your comment. I'm sorry for the low-level mistake. In the early design, I hoped that lnkc can also work on SMC-D, but in later tests I found out that we don't have SMC-D environment to test, so I have to canceled this logic. But dues to the rollback isn't thorough enough, leaving this issues, we are very sorry for that. > It is a SMC-D problem, that occurs while building up the connection. In smc_conn_create you set struct smc_lnk_cluster *lnkc = NULL. For the SMC-R path you do grab the pointer, for SMC-D that never happens. Still you are using this refernce for SMC-D => Crash. This problem can be reproduced using the SMC-D path. Here is an example console output: > > [ 779.516382] Unable to handle kernel pointer dereference in virtual kernel address space > [ 779.516389] Failing address: 0000000000000000 TEID: 0000000000000483 > [ 779.516391] Fault in home space mode while using kernel ASCE. > [ 779.516395] AS:0000000069628007 R3:00000000ffbf0007 S:00000000ffbef800 P:000000000000003d > [ 779.516431] Oops: 0004 ilc:2 [#1] SMP > [ 779.516436] Modules linked in: tcp_diag inet_diag ism mlx5_ib ib_uverbs mlx5_core smc_diag smc ib_core 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_ipv > 6 nf_defrag_ipv4 ip_set nf_tables n > [ 779.516470] CPU: 0 PID: 24 Comm: kworker/0:1 Not tainted 5.19.0-13940-g22a46254655a #3 > [ 779.516476] Hardware name: IBM 8561 T01 701 (z/VM 7.2.0) > > [ 779.522738] Workqueue: smc_hs_wq smc_listen_work [smc] > [ 779.522755] Krnl PSW : 0704c00180000000 000003ff803da89c (smc_conn_create+0x174/0x968 [smc]) > [ 779.522766] 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 > [ 779.522770] Krnl GPRS: 0000000000000002 0000000000000000 0000000000000001 0000000000000000 > [ 779.522773] 000000008a4128a0 000003ff803f21aa 000000008e30d640 0000000086d72000 > [ 779.522776] 0000000086d72000 000000008a412803 000000008a412800 000000008e30d650 > [ 779.522779] 0000000080934200 0000000000000000 000003ff803cb954 00000380002dfa88 > [ 779.522789] Krnl Code: 000003ff803da88e: e310f0e80024 stg %r1,232(%r15) > [ 779.522789] 000003ff803da894: a7180000 lhi %r1,0 > [ 779.522789] #000003ff803da898: 582003ac l %r2,940 > [ 779.522789] >000003ff803da89c: ba123020 cs %r1,%r2,32(%r3) > [ 779.522789] 000003ff803da8a0: ec1603be007e cij %r1,0,6,000003ff803db01c > > [ 779.522789] 000003ff803da8a6: 4110b002 la %r1,2(%r11) > [ 779.522789] 000003ff803da8aa: e310f0f00024 stg %r1,240(%r15) > [ 779.522789] 000003ff803da8b0: e310f0c00004 lg %r1,192(%r15) > [ 779.522870] Call Trace: > [ 779.522873] [<000003ff803da89c>] smc_conn_create+0x174/0x968 [smc] > [ 779.522884] [<000003ff803cb954>] smc_find_ism_v2_device_serv+0x1b4/0x300 [smc] > 01: HCPGSP2629I The virtual machine is placed in CP mode due to a SIGP stop from CPU 01. > 01: HCPGSP2629I The virtual machine is placed in CP mode due to a SIGP stop from CPU 00. > [ 779.522894] [<000003ff803cbace>] smc_listen_find_device+0x2e/0x370 [smc] > > > I'm going to send the review for the first patch right away (which is the one causing the crash), so far I'm done with it. The others are going to follow. Maybe you can look over the problem and come up with a solution, otherwise we are going to decide if we want to look into it as soon as I'm done with the reviews. Thank you for your patience. In the next revision, I will add additional judgment to protect the SMC-D environment, thanks for your comments. And Looking forward to your other comments, thanks again. D. Wythe
On 17.08.2022 06:55, D. Wythe wrote: > > > On 8/16/22 5:35 PM, Jan Karcher wrote: >> >> >> On 10.08.2022 19:47, D. Wythe wrote: >>> From: "D. Wythe" <alibuda@linux.alibaba.com> >>> >>> 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. >>> >> >> Thank you again for your submission! >> Let me give you a quick update from our side: >> We tested your patches on top of the net-next kernel on our s390 >> systems. They did crash our systems. After verifying our environment >> we pulled console logs and now we can tell that there is indeed a >> problem with your patches regarding SMC-D. So please do not integrate >> this change as of right now. I'm going to do more in depth reviews of >> your patches but i need some time for them so here is a quick a >> description of the problem: > > Sorry for the late reply, and thanks a lot for your comment. > > I'm sorry for the low-level mistake. In the early design, I hoped that > lnkc can also work on SMC-D, > but in later tests I found out that we don't have SMC-D environment to > test, so I have to canceled this logic. > But dues to the rollback isn't thorough enough, leaving this issues, we > are very sorry for that. > One more comment: If the only reason why you do not touch SMC-D is that you do not have the environment to test it we strongly encourage you to change it anyway. At some point doing kernel development, especially driver development you are going to reach the point where you do not have the environment to test it. It is on the maintainers to test those changes and verify that nothing is broken. So please: If testing is the only reason change SMC-D as well and we are going to test it for you verifying if it does work or not. Thank you Jan > >> It is a SMC-D problem, that occurs while building up the connection. >> In smc_conn_create you set struct smc_lnk_cluster *lnkc = NULL. For >> the SMC-R path you do grab the pointer, for SMC-D that never happens. >> Still you are using this refernce for SMC-D => Crash. This problem can >> be reproduced using the SMC-D path. Here is an example console output: >> >> [ 779.516382] Unable to handle kernel pointer dereference in virtual >> kernel address space >> [ 779.516389] Failing address: 0000000000000000 TEID: 0000000000000483 >> [ 779.516391] Fault in home space mode while using kernel ASCE. >> [ 779.516395] AS:0000000069628007 R3:00000000ffbf0007 >> S:00000000ffbef800 P:000000000000003d >> [ 779.516431] Oops: 0004 ilc:2 [#1] SMP >> [ 779.516436] Modules linked in: tcp_diag inet_diag ism mlx5_ib >> ib_uverbs mlx5_core smc_diag smc ib_core 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_ipv >> 6 nf_defrag_ipv4 ip_set nf_tables n >> [ 779.516470] CPU: 0 PID: 24 Comm: kworker/0:1 Not tainted >> 5.19.0-13940-g22a46254655a #3 >> [ 779.516476] Hardware name: IBM 8561 T01 701 (z/VM 7.2.0) >> >> [ 779.522738] Workqueue: smc_hs_wq smc_listen_work [smc] >> [ 779.522755] Krnl PSW : 0704c00180000000 000003ff803da89c >> (smc_conn_create+0x174/0x968 [smc]) >> [ 779.522766] 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 >> [ 779.522770] Krnl GPRS: 0000000000000002 0000000000000000 >> 0000000000000001 0000000000000000 >> [ 779.522773] 000000008a4128a0 000003ff803f21aa >> 000000008e30d640 0000000086d72000 >> [ 779.522776] 0000000086d72000 000000008a412803 >> 000000008a412800 000000008e30d650 >> [ 779.522779] 0000000080934200 0000000000000000 >> 000003ff803cb954 00000380002dfa88 >> [ 779.522789] Krnl Code: 000003ff803da88e: e310f0e80024 stg >> %r1,232(%r15) >> [ 779.522789] 000003ff803da894: a7180000 lhi %r1,0 >> [ 779.522789] #000003ff803da898: 582003ac l %r2,940 >> [ 779.522789] >000003ff803da89c: ba123020 cs >> %r1,%r2,32(%r3) >> [ 779.522789] 000003ff803da8a0: ec1603be007e cij >> %r1,0,6,000003ff803db01c >> >> [ 779.522789] 000003ff803da8a6: 4110b002 la >> %r1,2(%r11) >> [ 779.522789] 000003ff803da8aa: e310f0f00024 stg >> %r1,240(%r15) >> [ 779.522789] 000003ff803da8b0: e310f0c00004 lg >> %r1,192(%r15) >> [ 779.522870] Call Trace: >> [ 779.522873] [<000003ff803da89c>] smc_conn_create+0x174/0x968 [smc] >> [ 779.522884] [<000003ff803cb954>] >> smc_find_ism_v2_device_serv+0x1b4/0x300 [smc] >> 01: HCPGSP2629I The virtual machine is placed in CP mode due to a SIGP >> stop from CPU 01. >> 01: HCPGSP2629I The virtual machine is placed in CP mode due to a SIGP >> stop from CPU 00. >> [ 779.522894] [<000003ff803cbace>] smc_listen_find_device+0x2e/0x370 >> [smc] >> >> >> I'm going to send the review for the first patch right away (which is >> the one causing the crash), so far I'm done with it. The others are >> going to follow. Maybe you can look over the problem and come up with >> a solution, otherwise we are going to decide if we want to look into >> it as soon as I'm done with the reviews. Thank you for your patience. > > In the next revision, I will add additional judgment to protect the > SMC-D environment, > thanks for your comments. > > And Looking forward to your other comments, thanks again. > > D. Wythe >
On 8/18/22 12:52 AM, Jan Karcher wrote: > > > On 17.08.2022 06:55, D. Wythe wrote: >> >> >> On 8/16/22 5:35 PM, Jan Karcher wrote: >>> >>> >>> On 10.08.2022 19:47, D. Wythe wrote: >>>> From: "D. Wythe" <alibuda@linux.alibaba.com> >>>> >>>> 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. >>>> >>> >>> Thank you again for your submission! >>> Let me give you a quick update from our side: >>> We tested your patches on top of the net-next kernel on our s390 systems. They did crash our systems. After verifying our environment we pulled console logs and now we can tell that there is indeed a problem with your patches regarding SMC-D. So please do not integrate this change as of right now. I'm going to do more in depth reviews of your patches but i need some time for them so here is a quick a description of the problem: >> >> Sorry for the late reply, and thanks a lot for your comment. >> >> I'm sorry for the low-level mistake. In the early design, I hoped that lnkc can also work on SMC-D, >> but in later tests I found out that we don't have SMC-D environment to test, so I have to canceled this logic. >> But dues to the rollback isn't thorough enough, leaving this issues, we are very sorry for that. >> > > One more comment: > If the only reason why you do not touch SMC-D is that you do not have the environment to test it we strongly encourage you to change it anyway. > > At some point doing kernel development, especially driver development you are going to reach the point where you do not have the environment to test it. It is on the maintainers to test those changes and verify that nothing is broken. > > So please: > If testing is the only reason change SMC-D as well and we are going to test it for you verifying if it does work or not. > > Thank you > Jan Actually, this is not the only reason. The purpose of remove smc_server_lgr_pending & smc_client_lgr_pending is mainly to solve the problem of excessive lock granularity in SMC-R. In SMC-R those locks protect a complete CLC message exchange process, including sending and receiving. This results in a large number of connections having to be queued. But this is not the case with SMC-D. SMC-D releases the lock in advance before receiving the CLC message, which makes the problem less severe in SMC-D than in SMC-R. Of course, lnkc can be used for SMC-D, but considering that we have no way to test it, and it is not the core bottleneck of SMC-D, so we gave up it. I will fix the panic problem first in the next revison. If you have a strong demand for this feature, I may commit a separate PATCH to support it, dues to current patch is quite complicated, adding SMC-D support will exacerbate its complexity, which may affect the other reviewer progress. Thanks D. Wythe >> >>> It is a SMC-D problem, that occurs while building up the connection. In smc_conn_create you set struct smc_lnk_cluster *lnkc = NULL. For the SMC-R path you do grab the pointer, for SMC-D that never happens. Still you are using this refernce for SMC-D => Crash. This problem can be reproduced using the SMC-D path. Here is an example console output: >>> >>> [ 779.516382] Unable to handle kernel pointer dereference in virtual kernel address space >>> [ 779.516389] Failing address: 0000000000000000 TEID: 0000000000000483 >>> [ 779.516391] Fault in home space mode while using kernel ASCE. >>> [ 779.516395] AS:0000000069628007 R3:00000000ffbf0007 S:00000000ffbef800 P:000000000000003d >>> [ 779.516431] Oops: 0004 ilc:2 [#1] SMP >>> [ 779.516436] Modules linked in: tcp_diag inet_diag ism mlx5_ib ib_uverbs mlx5_core smc_diag smc ib_core 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_ipv >>> 6 nf_defrag_ipv4 ip_set nf_tables n >>> [ 779.516470] CPU: 0 PID: 24 Comm: kworker/0:1 Not tainted 5.19.0-13940-g22a46254655a #3 >>> [ 779.516476] Hardware name: IBM 8561 T01 701 (z/VM 7.2.0) >>> >>> [ 779.522738] Workqueue: smc_hs_wq smc_listen_work [smc] >>> [ 779.522755] Krnl PSW : 0704c00180000000 000003ff803da89c (smc_conn_create+0x174/0x968 [smc]) >>> [ 779.522766] 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 >>> [ 779.522770] Krnl GPRS: 0000000000000002 0000000000000000 0000000000000001 0000000000000000 >>> [ 779.522773] 000000008a4128a0 000003ff803f21aa 000000008e30d640 0000000086d72000 >>> [ 779.522776] 0000000086d72000 000000008a412803 000000008a412800 000000008e30d650 >>> [ 779.522779] 0000000080934200 0000000000000000 000003ff803cb954 00000380002dfa88 >>> [ 779.522789] Krnl Code: 000003ff803da88e: e310f0e80024 stg %r1,232(%r15) >>> [ 779.522789] 000003ff803da894: a7180000 lhi %r1,0 >>> [ 779.522789] #000003ff803da898: 582003ac l %r2,940 >>> [ 779.522789] >000003ff803da89c: ba123020 cs %r1,%r2,32(%r3) >>> [ 779.522789] 000003ff803da8a0: ec1603be007e cij %r1,0,6,000003ff803db01c >>> >>> [ 779.522789] 000003ff803da8a6: 4110b002 la %r1,2(%r11) >>> [ 779.522789] 000003ff803da8aa: e310f0f00024 stg %r1,240(%r15) >>> [ 779.522789] 000003ff803da8b0: e310f0c00004 lg %r1,192(%r15) >>> [ 779.522870] Call Trace: >>> [ 779.522873] [<000003ff803da89c>] smc_conn_create+0x174/0x968 [smc] >>> [ 779.522884] [<000003ff803cb954>] smc_find_ism_v2_device_serv+0x1b4/0x300 [smc] >>> 01: HCPGSP2629I The virtual machine is placed in CP mode due to a SIGP stop from CPU 01. >>> 01: HCPGSP2629I The virtual machine is placed in CP mode due to a SIGP stop from CPU 00. >>> [ 779.522894] [<000003ff803cbace>] smc_listen_find_device+0x2e/0x370 [smc] >>> >>> >>> I'm going to send the review for the first patch right away (which is the one causing the crash), so far I'm done with it. The others are going to follow. Maybe you can look over the problem and come up with a solution, otherwise we are going to decide if we want to look into it as soon as I'm done with the reviews. Thank you for your patience. >> >> In the next revision, I will add additional judgment to protect the SMC-D environment, >> thanks for your comments. >> >> And Looking forward to your other comments, thanks again. >> >> D. Wythe >>
From: "D. Wythe" <alibuda@linux.alibaba.com> 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 WQ_UNBOUND, we can obtain at least 4-5 times performance improvement, can 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 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 | 40 +++-- net/smc/smc_core.c | 447 +++++++++++++++++++++++++++++++++++++++++++++++------ net/smc/smc_core.h | 76 ++++++++- 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, 728 insertions(+), 147 deletions(-)