linux-kernel - Re: stuck tcp connections 2.6.26-rc7

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Message-ID: <2c0942db0806250816r123affb4x4ef17f4773180a10@mail.gmail.com>
Date:	Wed, 25 Jun 2008 08:16:20 -0700
From:	"Ray Lee" <ray-lk@...rabbit.org>
To:	"Justin Mattock" <justinmattock@...il.com>
Cc:	"Didier Raboud" <didier@...oud.com>, linux-kernel@...r.kernel.org,
	netdev@...r.kernel.org
Subject: Re: stuck tcp connections 2.6.26-rc7

On Tue, Jun 24, 2008 at 11:25 PM, Justin Mattock
<justinmattock@...il.com> wrote:
> On Tue, Jun 24, 2008 at 8:03 PM, Justin Mattock <justinmattock@...il.com> wrote:
>> On Tue, Jun 24, 2008 at 5:16 PM, Ray Lee <ray-lk@...rabbit.org> wrote:
>>> 2008/6/23 Justin Mattock <justinmattock@...il.com>:
>>>> On Mon, Jun 23, 2008 at 5:04 PM, Didier Raboud <didier@...oud.com> wrote:
>>>>> -----BEGIN PGP SIGNED MESSAGE-----
>>>>> Hash: SHA1
>>>>>
>>>>> Justin Mattock wrote:
>>>>>
>>>>>> On Mon, Jun 23, 2008 at 3:59 AM, Andrew Morton
>>>>>> <akpm@...ux-foundation.org> wrote:
>>>>>>> On Sun, 22 Jun 2008 18:09:16 +0000 "Justin Mattock"
>>>>>>> <justinmattock@...il.com> wrote:
>>>>>>>
>>>>>>>> Hello; I too am experiencing internet connectivity problems, for  a
>>>>>>>> while I thought
>>>>>>>> It was due to low bandwidth(or being ddos attacked) but yesterday I
>>>>>>>> noticed with watch netstat -ntu
>>>>>>>> send-Q was stuck on a number; the connection would not go to TIME_WAIT
>>>>>>>> resulting in music to pause, and t.v. to freeze.
>>>>>>>> In my experiences running xmms streaming music is fine, no problems,
>>>>>>>> but as soon as
>>>>>>>> you watch something with flash player the stream start's getting
>>>>>>>> really bad. In the past with older kernel's
>>>>>>>> I usually can watch t.v.(with flash) and stream music at the same time
>>>>>>>> without any trouble.
>>>>>>>> lately I've been Running the kernel in No forced Preemption with a
>>>>>>>> time frequency at 100. having the kernel set in this mode really shows
>>>>>>>> the connection problems, but if I change the preemption to another,
>>>>>>>> and bump up the timer frequency the poor internet connection is not as
>>>>>>>> bad(or stuck tcp) but still prevalent. more pops in the music, and
>>>>>>>> sudden internet loss for around five seconds, then goes back
>>>>>>>> So from over here streaming music has no problems from what I can see,
>>>>>>>> but as soon as I watch media, it becomes a mess.
>>>>>>>
>>>>>>> (cc netdev)
>>>>>>>
>>>>>>
>>>>>>
>>>>>> Cool, Thanks for sending the cc
>>>>>> regards;
>>>>>
>>>>> Hi,
>>>>>
>>>>> I get something like a similar bug: when pinging my local gateway, I loose
>>>>> packets (over wifi (iwl3945) ). Before the update to 2.6.26-rc7 (Debian), I
>>>>> had no such issues (which makes Internet browsing working but weirdly).
>>>>>
>>>>> I can't know for sure that my bug is related to the above, but suppose so.
>>>>> Please ask for details !
>>>>>
>>>>> Regards,
>>>>>
>>>>> Didier Raboud
>>>>> - --
>>>>
>>>> Cool;(cool as in I'm not the only one,not cool for sh*%y internet connections)
>>>> there is something definitely happening with the tcp connection.,
>>>> After looking more at the situation
>>>> I get a good connection when just streaming music, but as soon as I
>>>> watch with flash or even search through firefox
>>>> I'm getting a dead period of no internet, and then a few seconds later
>>>> no problems.Almost as if some timer in the code is missing something
>>>> or not firing off at the right time.
>>>> At this point I'm still uncertain with what is happening.
>>>> regards;
>>>
>>> If you leave a ping running as root to your local gateway from a
>>> console ( nice -n -10 ping -i 0.5 192.168.1.1
>>>  or whichever ip ), does it show dropouts?
>>>
>>
>> I'll give that a try and see what happens.
>> regards;
>>
>> --
>> Justin P. Mattock
>>
>
> Hmm, well I really don't know what to say with the tcp
> connection(issue), It seems to go in and out of phases i.g.
> at first running music, and t.v.(through flash) there's moments of
> pauses,(around 5 secs or so) then after a while
> the tcp seems to even itself out, but then after a while(5min or so)
> the same pauses begin. Maybe due to some missing packet, or
> some deadlock if this is proper to say.

On my system, I've noticed that the flashplugin can manage to starve
other processes in a pure scheduler sort of way, so you might try
running latencytop to see if there's some sort of issue there. OTOH,
I've noticed firefox itself hang for 3-15 seconds in the middle of a
read (just as you describe), with nothing else going on in the system,
so <shrug>. I've been blaming firefox, but I could be wrong.
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