netdev - Re: [PATCH net 4/4] net/smc: Fix wq mismatch issue caused by smc fallback

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Message-ID: <0c304740-dc87-c022-5397-96c6058732c0@linux.ibm.com>
Date:   Thu, 28 Oct 2021 16:16:17 +0200
From:   Karsten Graul <kgraul@...ux.ibm.com>
To:     Tony Lu <tonylu@...ux.alibaba.com>, davem@...emloft.net,
        kuba@...nel.org
Cc:     netdev@...r.kernel.org, linux-s390@...r.kernel.org,
        linux-rdma@...r.kernel.org, jacob.qi@...ux.alibaba.com,
        xuanzhuo@...ux.alibaba.com, guwen@...ux.alibaba.com,
        dust.li@...ux.alibaba.com
Subject: Re: [PATCH net 4/4] net/smc: Fix wq mismatch issue caused by smc
 fallback

On 27/10/2021 10:52, Tony Lu wrote:
> From: Wen Gu <guwen@...ux.alibaba.com>
> 
> A socket_wq mismatch issue may occur because of fallback.
> 
> When use SMC to replace TCP, applications add an epoll entry into SMC
> socket's wq, but kernel uses clcsock's wq instead of SMC socket's wq
> once fallback occurs, which means the application's epoll fd dosen't
> work anymore.
> 
> For example:
> server: nginx -g 'daemon off;'
> 
> client: smc_run wrk -c 1 -t 1 -d 5 http://11.200.15.93/index.html
> 
>   Running 5s test @ http://11.200.15.93/index.html
>     1 threads and 1 connections
>     Thread Stats   Avg      Stdev     Max   +/- Stdev
>       Latency     0.00us    0.00us   0.00us    -nan%
>       Req/Sec     0.00      0.00     0.00      -nan%
>     0 requests in 5.00s, 0.00B read
>   Requests/sec:      0.00
>   Transfer/sec:       0.00B
> 
> This patch fixes this issue by using clcsock's wq regardless of
> whether fallback occurs.
> 

I need to spend some more time testing and thinking about this fix.
Thank you.