dummynet dropping too many packets

[Luigi Rizzo]

On Tue, Oct 06, 2009 at 02:21:38PM +0500, rihad wrote:
> rihad wrote:
> >Julian Elischer wrote:
> >>rihad wrote:
> >>>Luigi Rizzo wrote:
> >>>>2. your test with 'ipfw allow ip from any to any' does not
> >>>>   prove that the interface queue is not saturating, because
> >>>>   you also remove the burstiness that dummynet introduces,
> >>>>   and so the queue is driven differently.
> >>>>
> >>>
> >>>How do I investigate and fix this burstiness issue?
> >>
> >>higher Hz rate?
> >>
> >
> >Rebooted with HZ=2000 10 minutes ago. Due to application design the ipfw 
> > table (pipe tablearg) was flushed, so there are now 350 (and increasing 
> >at a rate 1 per 1-2 seconds as I type this) or so users in the table, 
> >and not 4k as normally would be. The box is servicing 450+ mbit/s 
> >without a single drop. I want to monitor how things change once the 
> >number of users in ipfw tables gradually increases up to several thousands.
> >
> 
> It starts dropping packets at around 2000 online users (ipfw table 
> load). I've set up a shell script to monitor this:

once again:
you should check which pipes are dropping packets and whether
the number of drops indicated in the pipes matches the counts
indicated by netstat.

cheers
luigi


> # while :; do ipfw table 0 list | wc -l; netstat -s 2>/dev/null |fgrep 
> -w 'output packets dropped'; sleep 10; done
> 
> ... # all zeroes above this
>     1999
>         0 output packets dropped due to no bufs, etc.
>     2001
>         0 output packets dropped due to no bufs, etc.
>     2008
>         0 output packets dropped due to no bufs, etc.
>     2017
>         0 output packets dropped due to no bufs, etc.
>     2027
>         156 output packets dropped due to no bufs, etc.
>     2037
>         156 output packets dropped due to no bufs, etc.
>     2045
>         156 output packets dropped due to no bufs, etc.
>     2372
>         202 output packets dropped due to no bufs, etc.
>     2377
>         207 output packets dropped due to no bufs, etc.
>     2391
>         338 output packets dropped due to no bufs, etc.
>     2402
>         394 output packets dropped due to no bufs, etc.
>     2415
>         531 output packets dropped due to no bufs, etc.
>     2421
>         725 output packets dropped due to no bufs, etc.
> 
> 
> Is there some limit on the number of IP addresses in an ipfw table?
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