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IV35154: UNNECESSARY LARGESEND THROTTLING RESULTING IN POOR PERFORMANCE

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APAR status

  • Closed as program error.

Error description

  • Largesend can stop sending data even though there is
enough
data in the socket send buffer and the receive window and
congestion window are both non-zero and allow a send.
This
results in poor performance when largesend is turned on.
Further performance is improved vastly when largesend is
turned off.

This will likely occur when there are packet drops when
doing largesend and when the receive buffer size is
really
large.

Local fix

  • Reduce receive window on receiver or make it equal to the
sendspace on the sender. This will alleviate the
performance issue but not fix it completely.

Problem summary

  • When largesend is ON, customer will face poor network
performance issue.

Problem conclusion

  • When largesend is ON, if we have larger amount of data on the
pipe and less amount of data to be send, we will wait to
accumulate more data on transport layer. If have data whose
length is greater than 40% of the outstanding data, we will be
 sending data without waiting for any acknowledgement.

Temporary fix

  • 



Comments


    

  • 



APAR Information




    

  • APAR number
    IV35154
    • 

  • Reported component name
    AIX V7.1
    • 

  • Reported component ID
    5765H4000
    • 

  • Reported release
    710
    • 

  • Status
    CLOSED  PER
    • 

  • PE
    NoPE
    • 

  • HIPER
    NoHIPER
    • 

  • Submitted date
    2013-01-15
    • 

  • Closed date
    2013-01-15
    • 

  • Last modified date
    2013-04-25
    • 





    

  • APAR is sysrouted FROM one or more of the following:
    

    
IV00648
    

    • 

  • APAR is sysrouted TO one or more of the following:
    

    • 



Fix information


    

  • Fixed component name
    AIX V7.1
    • 

  • Fixed component ID
    5765H4000
    • 



Applicable component levels


    

  • R710  PSY  U854832
       UP13/04/25  I  1000
    • 



PTF to Fileset Mapping








      
              
                            

              

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Document Information


            

            


                        

            Modified date:
            

            25 April 2013
            

            
                      

        


        

        


      

    

  



    

  

  
    
            

          
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