Re: ixg(4) performances

[Matthias Scheler <tron%zhadum.org.uk@localhost>]

On Fri, Jul 04, 2014 at 02:43:19PM +0000, Emmanuel Dreyfus wrote:
> I quote myself here:
> 
> On Wed, Jul 02, 2014 at 02:05:53PM +0000, Emmanuel Dreyfus wrote:
> > TCP connection established.
> > Packet size  1k bytes:  114938 KByte/s Tx,  114816 KByte/s Rx.
> > Packet size  2k bytes:  114924 KByte/s Tx,  114868 KByte/s Rx.
> > Packet size  4k bytes:  114871 KByte/s Tx,  114901 KByte/s Rx.
> > Packet size  8k bytes:  114877 KByte/s Tx,  114900 KByte/s Rx.
> > Packet size 16k bytes:  114882 KByte/s Tx,  114914 KByte/s Rx.
> > Packet size 32k bytes:  114881 KByte/s Tx,  114905 KByte/s Rx.
> 
> ioperf reports awful perfs.  But netperf says:
> 
> root@saccharose#  netperf -H 10.103.101.117
> TCP STREAM TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to 10.103.101.117 
> (10.103.101.117) port 0 AF_INET
> Recv   Send    Send                          
> Socket Socket  Message  Elapsed              
> Size   Size    Size     Time     Throughput  
> bytes  bytes   bytes    secs.    10^6bits/sec  
> 
>  32768  32768  32768    10.01    1152.76   
> 
> This look much better: maximum bandwith is 1200 Mb/s as I understand.
> 
> How can this be explained?

Probably by a various factors:
1.) Lack of SMP scalabity in the network stack.
2.) No MSIE-X support.
3.) No RSS support in the driver.

You will also struggle to sature a 10Gb/s link with a single TCP connection
in general.

        Kind regards

-- 
Matthias Scheler                                 https://zhadum.org.uk/