Re: Performance problems with squeeze kernel

[Thorsten Giese <t.giese@anw.de>]

Am 31.08.2011 14:09, schrieb Ben Hutchings:
>> I think I found a performance issue in the kernel (2.6.32/amd64) of the
>> squeeze release.
>>
>> I tested from different servers and each time made a wget of a 16 MB
>> file from a remote co-location which is connected with gigabit (but the
>> issue showed also on a 32MBit/s "dial-up" cable connection).
>>
>> The squeeze system starts the transfer significantly slower and takes
>> longer to get faster over time (on a 2GB file the maximum was reached
>> after 12 seconds). The lenny system reaches this maxium very fast so the
>> overall time drops from 2.4s to 0.4s. It could be, this is related to
>> changes in TCP/IP behaviour. I could not see this behaviour in the same
>> subnet, it shows up, as soon as routing is involved in the connection.
> [...]
>
> Which network driver are you using?
>
> Is there any packet loss?  Run 'netstat -s | grep retransmited' to
> check this.


I checked and I am using the e1000e on all affected systems. I checked
on a squeeze system with the r8169 driver and the problem seems not to
appear there.

Your netstat command says:  "4096 segments retransmited" before the wget
and the same after it.

I checked with mtr and ping multiple times that there was no packet
loss, between and during the requests as part of my research in the past.

Thorsten