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Message-ID: <2d138d78-1ebb-92b0-c6c5-9e43b5ee941b@linux.alibaba.com>
Date: Mon, 4 Dec 2023 11:52:21 +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 2023/12/4 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
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