Date: Wed, 13 Dec 2023 21:06:53 +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 2023/12/5 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.

The HTTP GET is transfered by SMC stack through shared memory. So they
can't be captured by tcpdump.

> 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
> 
> 
> 

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