Date: Mon, 05 Oct 2009 18:08:47 +0500 From: rihad <rihad@mail.ru> To: Luigi Rizzo <rizzo@iet.unipi.it> Cc: freebsd-net@freebsd.org Subject: Re: dummynet dropping too many packets Message-ID: <4AC9EFDF.4080302@mail.ru> In-Reply-To: <20091005123230.GA64167@onelab2.iet.unipi.it> References: <20091005061025.GB55845@onelab2.iet.unipi.it> <4AC9B400.9020400@mail.ru> <20091005090102.GA70430@svzserv.kemerovo.su> <4AC9BC5A.50902@mail.ru> <20091005095600.GA73335@svzserv.kemerovo.su> <4AC9CFF7.3090208@mail.ru> <20091005110726.GA62598@onelab2.iet.unipi.it> <4AC9D87E.7000005@mail.ru> <20091005120418.GA63131@onelab2.iet.unipi.it> <4AC9E29B.6080908@mail.ru> <20091005123230.GA64167@onelab2.iet.unipi.it>
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Luigi Rizzo wrote:
> On Mon, Oct 05, 2009 at 05:12:11PM +0500, rihad wrote:
>> Luigi Rizzo wrote:
>>> On Mon, Oct 05, 2009 at 04:29:02PM +0500, rihad wrote:
>>>> Luigi Rizzo wrote:
>>> ...
>>>>> you keep omitting the important info i.e. whether individual
>>>>> pipes have drops, significant queue lenghts and so on.
>>>>>
>>>> Sorry. Almost everyone has 0 in the last Drp column, but some have above
>>>> zero. I'm not just sure how this can be helpful to anyone.
>>> because you were complaining about 'dummynet causing drops and
>>> waste of bandwidth'.
>>> Now, drops could be due to either
>>> 1) some saturation in the dummynet machine (memory shortage, cpu
>>> shortage, etc.) which cause unwanted drops;
>>>
>> I too think the box is hitting some other global limit and dropping
>> packets. If not, then how come that between 4a.m. and 10a.m. when the
>> traffic load is at 250-330 mbit/s there isn't a single drop?
>
> there may be different reasons, e.g. the big offenders were
> idle when you saw no drops. You still do not have enough
> information on which packets are dropped and where,
> so you cannot prove your assumptions.
>
> Also, below:
> 1. increasing the queue size won't help at all. Those
> who overflow a queue of 1000 slots will also overflow
> a queue of 10k slots.
>
> 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.
>
There's one thing I noticed:
net.inet.ip.dummynet.io_pkt_drop doesn't grow! But still around 400
packets dropped per second.
net.inet.ip.dummynet.tick_lost is always zero
net.inet.ip.dummynet.tick_diff: grows at about 50 per second.
net.inet.ip.dummynet.tick_adjustment: grows at about 5 per second.
How do I investigate and fix this burstiness issue?
$ netstat -i
Name Mtu Network Address Ipkts Ierrs Opkts
Oerrs Coll
bce0 1500 <Link#1> 00:1d:09:xx:xx:xx 24777049059 0 75426020
0 0
bce0 1500 xx.xx.xx.xx/xx my.hostname 159293969 - 75282225
- -
bce1 1500 <Link#2> 00:1d:09:xx:xx:xx 724725 0 24514919344
0 0
bce1 1500 192.168.94.0 local.hostname 656243 - 83024869
- -
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