Network slowdown on lo0 introduced with svn186119/186121

[Christian Gusenbauer]

Hi Qing!

Amanda uses two processes which communicate using a localhost-based tcp 
connection. I assume one of them is dump'ing the partition and sends the 
blocks to the other process, which stores them on tape or to another hard 
disk (which is the way I configured it). I did not configure amanda to use 
the localhost address though.

My method of measurement is rather simple: a backup of my root partition (~ 
800 MB) lasts about a 3 minutes with a kernel based on revision 186107. Using 
a kernel based on revision 186121 a backup of the same partition lasts more 
than 9 hours! I tested kernels of revisions 186133, 186150, 186176 and HEAD 
of today morning CET - all showing the same slowdown. Revisions 185984, 
186061 and 186107 are ok.

I did some tests with the 'echo' and 'discard' services of inetd, too, but I 
was not able to reproduce this slowdown.

Many thanks,
Christian.

On Sunday 28 December 2008, Li, Qing wrote:
> Hi Christian,
>
> Is the loopback address or an address that is assigned to
> an interface used by amanda? Would it be possible for you
> to give me some information on the tests you performed and
> on your method of measurement?
>
> Thanks,
>
> -- Qing
>
> ________________________________
>
> From: owner-freebsd-current at freebsd.org on behalf of Christian Gusenbauer
> Sent: Sun 12/28/2008 9:56 AM
> To: freebsd-current at freebsd.org
> Subject: Network slowdown on lo0 introduced with svn186119/186121
>
>
>
> Hi!
>
> Today I built a new kernel on current and experienced a massive network
> slowdown on lo0 when doing a backup using amanda. I made some tests and it
> seems that the commits 186119 and 186121 to the svn repository are causing
> it. A kernel based on revision 186107 runs fine and all kernels starting
> with revison 186119 do not.
>
> This slowdown seems to appear only on the loopback interface, not on my lan
> interface.
>
> Is this a known issue?
>
> Regards,
> Christian.
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