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From:   liuyacan@corp.netease.com
To:     kgraul@linux.ibm.com, davem@davemloft.net, edumazet@google.com,
        kuba@kernel.org, pabeni@redhat.com
Cc:     linux-s390@vger.kernel.org, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org, ubraun@linux.ibm.com,
        tonylu@linux.alibaba.com
Subject: SMC-R problem under multithread
Date:   Mon, 30 May 2022 11:16:04 +0800
Message-Id: <20220530031604.144875-1-liuyacan@corp.netease.com>
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Hi experts,

  I recently used memcached to test the performance of SMC-R relative to TCP, but the results 
  are confusing me. When using multithread on the server side, the performance of SMC-R is not as good as TCP.
    
  Specifically, I tested 4 scenarios with server thread: 1\2\4\8. The client uses 8threads fixedly. 
  
  server: (smc_run) memcached -t 1 -m 16384 -p [SERVER-PORT] -U 0 -F -c 10240 -o modern
  client: (smc-run) memtier_benchmark -s [SERVER-IP] -p [SERVER-PORT] -P memcache_text --random-data --data-size=100 --data-size-pattern=S --key-minimum=30 --key-maximum=100  -n 5000000 -t 8
  
  The result is as follows:
  
  SMC-R:
  
  server-thread    ops/sec  client-cpu server-cpu
      1             242k        220%         97%
      2             362k        241%        128%
      4             378k        242%        160%
      8             395k        242%        210%
      
  TCP:
  server-thread    ops/sec  client-cpu server-cpu
      1             185k       224%         100%
      2             435k       479%         200%
      4             780k       731%         400%
      8             938k       800%         659%                   
   
  It can be seen that as the number of threads increases, the performance increase of SMC-R is much slower than that of TCP.

  Am I doing something wrong? Or is it only when CPU resources are tight that SMC-R has a significant advantage ?  
  
  Any suggestions are welcome.


Thanks & Regards,
Yacan.