Message-ID: <699c9271-9c6d-0884-048d-6a9b83fb8619@linux.alibaba.com>
Date: Wed, 13 Dec 2023 20:59:43 +0800
From: Wen Gu <guwen@...ux.alibaba.com>
To: shaozhengchao <shaozhengchao@...wei.com>
Cc: "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
 yuehaibing <yuehaibing@...wei.com>, "Libin (Huawei)"
 <huawei.libin@...wei.com>, Dust Li <dust.li@...ux.alibaba.com>,
 tonylu_linux <tonylu@...ux.alibaba.com>, "D. Wythe"
 <alibuda@...ux.alibaba.com>
Subject: Re: [question] smc: how to enable SMC_LO feature

On 2023/12/13 17:00, shaozhengchao wrote:
> 
> 
> On 2023/12/5 14:45, shaozhengchao wrote:
>>
>>
>> On 2023/12/4 12:06, shaozhengchao wrote:
>>>
>>>
>>> On 2023/12/4 11:52, Wen Gu wrote:
>>>>
>>>> On 2023/12/4 11:22, shaozhengchao wrote:
>>>>>
>>>>>
>>>>> On 2023/11/23 14:15, shaozhengchao wrote:
>>>>>>
>>>>>>
>>>>>> On 2023/11/23 10:21, Wen Gu wrote:
>>>>>>>
>>>>>>>
>>>>>>> On 2023/11/21 20:14, shaozhengchao wrote:
>>>>>>>> Hi Wen Gu:
>>>>>>>> Currently, I am interested in the SMC_LOOPBACK feature proposed
>>>>>>>> by you. Therefore, I use your patchset[1] to test the SMC_LO feature on
>>>>>>>> my x86_64 environment and kernel is based on linux-next, commit: 5ba73bec5e7b.
>>>>>>>> The test result shows that the smc_lo feature cannot be enabled. Here's
>>>>>>>> my analysis:
>>>>>>>>
>>>>>>>> 1. Run the following command to perform the test, and then capture
>>>>>>>> packets on the lo device.
>>>>>>>> - serv:  smc_run taskset -c <cpu> sockperf sr --tcp
>>>>>>>> - clnt:  smc_run taskset -c <cpu> sockperf  tp --tcp --msg-size=64000 -i 127.0.0.1 -t 30
>>>>>>>>
>>>>>>>> 2. Use Wireshark to open packets. It is found that the VCE port replies with
>>>>>>>> SMC-R-Deline packets.
>>>>>>>> [cid:image001.png@...A1CB4.F1052C30]
>>>>>>>>
>>>>>>>> 3. Rx
>>>>>>>> When smc_listen_work invokes smc_listen_v2_check, the VCE port returns
>>>>>>>> a Decline packet because eid_cnt and flag.seid in the received packet are both 0.
>>>>>>>>
>>>>>>>> 4. Tx
>>>>>>>> In smc_clc_send_proposal,
>>>>>>>> v2_ext->hdr.eid_cnt = smc_clc_eid_table.ueid_cnt;
>>>>>>>> v2_ext->hdr.flag.seid = smc_clc_eid_table.seid_enabled;
>>>>>>>>
>>>>>>>> When smc_clc_init, ueid_cnt=0, and in the x86_64 environment, seid_enabled is
>>>>>>>> always equal to 0.
>>>>>>>>
>>>>>>>> So, I must call smc_clc_ueid_add function to increase ueid count?
>>>>>>>> But I don't see where operations can be added, may I missed something?
>>>>>>>>
>>>>>>>
>>>>>>> Hi Zhengchao Shao,
>>>>>>>
>>>>>>> Yes. When using SMC-D in non-s390 architecture (like x86 here), A common
>>>>>>> UEID should be set. It can be set by following steps:
>>>>>>>
>>>>>>> - Install smc-tools[1].
>>>>>>>
>>>>>>> - Run # smcd ueid add <ueid> in loopback test environment.
>>>>>>>
>>>>>>>    EID works as an ID to indicate the max communication space of SMC. When SEID is
>>>>>>>    unavailable, an UEID is required.
>>>>>>>
>>>>>> Hi Wen Gu:
>>>>>>      Thank you for your reply. This is very useful for me. And I will
>>>>>> be happy to learn from it.
>>>>>>
>>>>>> Thanks
>>>>>>
>>>>>> Zhengchao Shao
>>>>>>> - Then run the test.
>>>>>>>
>>>>>>> Hope this works for you :)
>>>>>>>
>>>>>>> [1] https://github.com/ibm-s390-linux/smc-tools
>>>>>>>
>>>>>>> Regards,
>>>>>>> Wen Gu
>>>>>>>
>>>>>>>> Could you give me some advice? Thanks very much.
>>>>>>>>
>>>>>>>> Zhengchao Shao
>>>>>>>>
>>>>>>>>
>>>>>>>> [1]link: 
>>>>>>>> https://patchwork.kernel.org/project/netdevbpf/cover/1695568613-125057-1-git-send-email-guwen@linux.alibaba.com/
>>>>>>>>
>>>>>>>
>>>>>>
>>>>>>
>>>>> Hi Wen Gu:
>>>>>      I have test as following, but the performance is really
>>>>> degraded. Now I have no idea.
>>>>> 1. add ueid
>>>>> run: smcd ueid add 16
>>>>> kernel message:
>>>>> [ 5252.009133] NET: Registered PF_SMC protocol family
>>>>> [ 5252.009233] smc: adding smcd device smc_lo with pnetid
>>>>> 2. start server
>>>>> smc_run taskset -c 1 sockperf sr --tcp
>>>>> 3. start client
>>>>> smc_run taskset -c 3 sockperf tp  --tcp --msg-size=64000 -i 127.0.0.1 -t 30
>>>>>
>>>>> The test results are as follows:
>>>>>                TCP                  SMC-lo
>>>>> Bandwidth(MBps)         1890.56               1300.41(-31.22%)
>>>>>
>>>>> I didn't find a better direction when I initially positioned it. No
>>>>> error is recorded in the kernel log, and the smcd statistics are normal.
>>>>> [root@...alhost smc-tools]# smcd stats
>>>>> SMC-D Connections Summary
>>>>>    Total connections handled             2
>>>>>    SMC connections                       2
>>>>>    Handshake errors                      0
>>>>>    Avg requests per SMC conn       1277462.0
>>>>>    TCP fallback                          0
>>>>>
>>>>> RX Stats
>>>>>    Data transmitted (Bytes)    40907328000 (40.91G)
>>>>>    Total requests                  1277190
>>>>>    Buffer full                          45 (0.00%)
>>>>>              8KB    16KB    32KB    64KB   128KB   256KB   512KB >512KB
>>>>>    Bufs        0       0       0       2       0       0 0       0
>>>>>    Reqs   638.0K       0       0  639.2K       0       0 0       0
>>>>>
>>>>> TX Stats
>>>>>    Data transmitted (Bytes)    40907328000 (40.91G)
>>>>>    Total requests                  1277734
>>>>>    Buffer full                      638239 (49.95%)
>>>>>    Buffer full (remote)                  0 (0.00%)
>>>>>    Buffer too small                      0 (0.00%)
>>>>>    Buffer too small (remote)             0 (0.00%)
>>>>>              8KB    16KB    32KB    64KB   128KB   256KB   512KB >512KB
>>>>>    Bufs        0       0       0       0       0       0 0       0
>>>>>    Reqs        0       0       0  1.278M       0       0 0       0
>>>>>
>>>>> Extras
>>>>>    Special socket calls                  1
>>>>>
>>>>> I captured the perf information and found that the percentage of
>>>>> rep_movs_alternative and _raw_spin_unlock_irqrestore functions was high
>>>>> during tx and rx.
>>>>> 36.12%  [kernel]         [k]rep_movs_alternative
>>>>> 14.23%  [kernel]         [k]_raw_spin_unlock_irqrestore
>>>>>
>>>>> I've attached the flame map. Could you help analyze it? What I missed?
>>>>> Thanks.
>>>>
>>>> Hi Zhengchao Shao,
>>>>
>>>> Since sndbuf and RMB in SMC are pre-alloced ringbuf and won't grow dynamically
>>>> like TCP, it is necessary to appropriately increase the default value of smc
>>>> sk_sndbuf and sk_rcvbuf before testing throughput.
>>>>
>>>> Set this and try again:
>>>>
>>>> # sysctl -w net.smc.wmem=1048576
>>>> # sysctl -w net.smc.rmem=1048576
>>>>
>>>> (The initial value of wmem and rmem are 64K)
>>>>
>>>> Regards,
>>>> Wen Gu
>>>>
>>>>>
>>>>> Zhengchao Shao
>>> Hi Wen Gu:
>>>      It solves the issue. Thank you very much.
>>>
>>> Zhengchao Shao
>>>
>> Hi Wen Gu:
>>    I've tested all the performance test items in the patchset. The
>> performance improvement is to be expected, except for nignx.
>> My VM is configured with 48 cores and 32 GB memory. Therefore, run
>> the following command:
>> <smc_run> nignx
>> <smc_run>./wrk -t 96 -c 1000 -d 30 http://127.0.0.1:80
>>
>> The test results are as follows:
>>                          TCP                         SMC_lo
>> Requests/s           309425.42               135547.25(-56.19%)
>> The performance decreases by 56.19%.
>>
>> I capture packets and find that wrk can perform HTTP GET after each
>> connect when smc_loopback is disabled.
>> However, when smc_loopback is enabled, there is no HTTP GET behavior.
>> I wonder if there is some compatibility problem with the SMC protocol when encapsulate packet? Could you give me some 
>> advice?
>> In the attachment, I captured some of the packets.
>> nosmc_nginx.pcap is for SMC disabled and smc_nginx.pcap is for SMC
>> enabled.
>> Thank you very much.
>>
>> Zhengchao Shao
>>
>>
>>
> Hi Wen Gu:
>      When the VM is configured with 8 cores and 16 GB memory, run
> the following command:
> <smc_run> nignx
> <smc_run>./wrk -t 8 -c 1000 -d 30 http://127.0.0.1:80
> the test data is as follows:
>           TCP          SMC_lo
> Requests/s  66056.66    94526.66(43.10%)
> 
> But When the VM is configured with 48 cores and 32 GB memory, run
> the following command:
> <smc_run> nignx
> <smc_run>./wrk -t 96 -c 1000 -d 30 http://127.0.0.1:80
> the test data is as follows:
>           TCP          SMC_lo
> Requests/s  309425.42     135547.25(-56.19%)
> 
> It seems that in the scenario with a large number of CPU cores,
> performance is not optimized, but performance deteriorates. What I
> missed?
> Thank you.
> 
> Zhengchao Shao

Hi Zhengchao,

I failed to reproduce this large regression. Could you please share some
information about your test environment?

- The nginx configure.
- The guest(VM) cpu topology.
- The host(physical machine) cpu topology.
- The mapping relationship between vcpu of guest(VM) and physical cpu of host.
- The cpu usage (top) when regression happens.

Thank you.

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