Date: Thu, 14 Dec 2023 11:17:05 +0800
From: shaozhengchao <shaozhengchao@...wei.com>
To: Wen Gu <guwen@...ux.alibaba.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 20:59, Wen Gu wrote:
> 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?
> 
Hi Wen Gu:
> - The nginx configure.
See the nginx.conf file in the attachment.
> - The guest(VM) cpu topology.
See the vm_cpuinfo file in the attachment.
> - The host(physical machine) cpu topology.
See the host_cpuinfo file in the attachment.
> - The mapping relationship between vcpu of guest(VM) and physical cpu of 
> host.
See the cpu_map file in the attachment.
> - The cpu usage (top) when regression happens.
> 
See the perf_top and perf.svg file in the attachment.
> Thank you.
>

Thank you very much.

Zhengchao Shao
View attachment "cpu_map" of type "text/plain" (7215 bytes)

View attachment "host_cpuinfo" of type "text/plain" (54754 bytes)

View attachment "nginx.conf" of type "text/plain" (2342 bytes)

Download attachment "perf.svg" of type "image/svg+xml" (267364 bytes)

View attachment "perf_top" of type "text/plain" (1370 bytes)

View attachment "vm_cpuinfo" of type "text/plain" (35624 bytes)

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