Re[4]: serious networking (em) performance (ggate and NFS) problem

 Thank you, Matt.
> 
>     Very interesting, but the only reason you get lower results is simply
>     because the TCP window is not big enough.  That's it.
> 

 Yes, I knew that adjusting TCP window size is important to use up a link.
 However I wanted to show adjusting the parameters of Interrupt
 Moderation affects network performance.

 And I think a packet loss was occured by enabled Interrupt Moderation.
 The mechanism of a packet loss in this case is not cleared, but I think
 inappropriate TCP window size is not the only reason.

 I found TCP throuput improvement at disabled Interrupt Moderation is related
 to congestion avoidance phase of TCP. Because these standard deviations are
 decreased when Interrupt Moderation is disabled.

 The following two results are outputs of `iperf -P 10'. without TCP
 window size adjustment too. I think, the difference of each throughput
 at same measurement shows congestion avoidance worked.

o with default setting of Interrupt Moderation.
> [ ID] Interval       Transfer     Bandwidth
> [ 13]  0.0-10.0 sec  80.1 MBytes  67.2 Mbits/sec
> [ 11]  0.0-10.0 sec   121 MBytes   102 Mbits/sec
> [ 12]  0.0-10.0 sec  98.9 MBytes  83.0 Mbits/sec
> [  4]  0.0-10.0 sec  91.8 MBytes  76.9 Mbits/sec
> [  7]  0.0-10.0 sec   127 MBytes   106 Mbits/sec
> [  5]  0.0-10.0 sec   106 MBytes  88.8 Mbits/sec
> [  6]  0.0-10.0 sec   113 MBytes  94.4 Mbits/sec
> [ 10]  0.0-10.0 sec   117 MBytes  98.2 Mbits/sec
> [  9]  0.0-10.0 sec   113 MBytes  95.0 Mbits/sec
> [  8]  0.0-10.0 sec  93.0 MBytes  78.0 Mbits/sec
> [SUM]  0.0-10.0 sec  1.04 GBytes   889 Mbits/sec

o with disabled Interrupt Moderation.
> [ ID] Interval       Transfer     Bandwidth
> [  7]  0.0-10.0 sec   106 MBytes  88.9 Mbits/sec
> [ 10]  0.0-10.0 sec   107 MBytes  89.7 Mbits/sec
> [  8]  0.0-10.0 sec   107 MBytes  89.4 Mbits/sec
> [  9]  0.0-10.0 sec   107 MBytes  90.0 Mbits/sec
> [ 11]  0.0-10.0 sec   106 MBytes  89.2 Mbits/sec
> [ 12]  0.0-10.0 sec   104 MBytes  87.6 Mbits/sec
> [  4]  0.0-10.0 sec   106 MBytes  88.7 Mbits/sec
> [ 13]  0.0-10.0 sec   106 MBytes  88.9 Mbits/sec
> [  5]  0.0-10.0 sec   106 MBytes  88.9 Mbits/sec
> [  6]  0.0-10.0 sec   107 MBytes  89.9 Mbits/sec
> [SUM]  0.0-10.0 sec  1.04 GBytes   891 Mbits/sec


 But, By decreasing TCP windows size, it could avoid.
o with default setting of Interrupt Moderation and iperf -P 10 -w 28.3k
> [ ID] Interval       Transfer     Bandwidth
> [ 12]  0.0-10.0 sec   111 MBytes  93.0 Mbits/sec
> [  4]  0.0-10.0 sec   106 MBytes  88.8 Mbits/sec
> [ 11]  0.0-10.0 sec   107 MBytes  89.9 Mbits/sec
> [  9]  0.0-10.0 sec   109 MBytes  91.6 Mbits/sec
> [  5]  0.0-10.0 sec   109 MBytes  91.5 Mbits/sec
> [ 13]  0.0-10.0 sec   108 MBytes  90.8 Mbits/sec
> [ 10]  0.0-10.0 sec   107 MBytes  89.7 Mbits/sec
> [  8]  0.0-10.0 sec   110 MBytes  92.3 Mbits/sec
> [  6]  0.0-10.0 sec   111 MBytes  93.2 Mbits/sec
> [  7]  0.0-10.0 sec   108 MBytes  90.6 Mbits/sec
> [SUM]  0.0-10.0 sec  1.06 GBytes   911 Mbits/sec


 Measureing TCP throughput was not appropriate way to indicate an effect
 of Interrupt Moderation clearly. It's my mistake. TCP is too
 complicated. :)

-- 
Shunsuke SHINOMIYA <shino_at_fornext.org>