Re: dhclient taking all cpu

From: Eric Anderson <anderson_at_centtech.com>
Date: Wed, 27 Jul 2005 08:40:44 -0500
Eric Anderson wrote:
> Brooks Davis wrote:
> 
>> On Tue, Jul 26, 2005 at 06:53:17PM -0400, Jung-uk Kim wrote:
>>
>>> On Tuesday 26 July 2005 04:00 pm, Wilko Bulte wrote:
>>>
>>>> On Tue, Jul 26, 2005 at 12:33:24PM -0700, Brooks Davis wrote..
>>>>
>>>>
>>>>> On Mon, Jul 25, 2005 at 10:39:09PM -0400, Mike Jakubik wrote:
>>>>>
>>>>>> On Mon, July 25, 2005 9:54 pm, Brooks Davis said:
>>>>>>
>>>>>>>>> Probably something wrong with your interface, but you
>>>>>>>>> havent't provided any useful information so who knows.  At
>>>>>>>>> the very least, I need to know what interface you are
>>>>>>>>> running on, something about it's status, and if both
>>>>>>>>> dhclient processes are running.
>>>>>>>>
>>>>>>>>
>>>>>>>> The interface is xl0 (3Com 3c905C-TX Fast Etherlink XL), and
>>>>>>>> it worked in this machine fine for as long as i remember.
>>>>>>>> This seems to have happened since a recent cvsup and
>>>>>>>> buildworld from ~6-BETA to 7-CURRENT. I rebooted three
>>>>>>>> times, and the problem occured rougly a minute after bootup.
>>>>>>>> On the fourth time however, it seems to be ok so far.
>>>>>>>
>>>>>>>
>>>>>>> That sounds like a problem with the code that handles the
>>>>>>> link state notifications in the interface driver.  The
>>>>>>> notifications are a reletivly new feature that we're only now
>>>>>>> starting to use heavily so there are going to be bumps in the
>>>>>>> road.  It would be intresting to know if you see link state
>>>>>>> messages promptly if you plug and unplug the network cable.
>>>>>>
>>>>>>
>>>>>> It seems to be back at it again, this time it took longer to
>>>>>> kick in. Here is a "ps auxw|grep dhclient" :
>>>>>>
>>>>>> _dhcp      219 93.5  0.2  1484  1136  ??  Rs    8:49PM  5:06.00 
>>>>>> dhclient: xl0 (dhclient)
>>>>>> root       193  0.0  0.2  1484  1088  d0- S     8:49PM  0:00.02 
>>>>>> dhclient: xl0 [priv] (dhclient)
>>>>>>
>>>>>> top:
>>>>>>
>>>>>>  PID USERNAME      THR PRI NICE   SIZE    RES STATE    TIME  WCPU 
>>>>>> COMMAND 219 _dhcp           1 129    0  1484K  1136K RUN    9:33 
>>>>>> 94.24% dhclient
>>>>>>
>>>>>> Nothing in dmesg about link state changes on xl0. Unplugging
>>>>>> and replugging the network cable results in link state
>>>>>> notification within a couple seconds.
>>>>>
>>>>>
>>>>> Could you see what happens if you run dhclient in the foreground?
>>>>> Just running "dhclient -d xl0" should do it.  I'd like to know
>>>>> what sort of output it's generating.
>>>>
>>>>
>>>> In my case it is not displaying anything:
>>>>
>>>>
>>>> chuck#dhclient -d ath0
>>>> DHCPREQUEST on ath0 to 255.255.255.255 port 67
>>>> DHCPACK from 192.168.5.254
>>>> bound to 192.168.5.20 -- renewal in 21600 seconds.
>>>>
>>>> <nothing>
>>>>
>>>> I can tell the phenomenon occurs when my laptop fan springs to
>>>> life:
>>>>
>>>> CPU states: 96.5% user,  0.0% nice,  2.7% system,  0.8% interrupt, 
>>>> 0.0% idle
>>>> Mem: 48M Active, 28M Inact, 50M Wired, 680K Cache, 34M Buf, 115M
>>>> Free Swap: 257M Total, 257M Free
>>>>
>>>>  PID USERNAME  THR PRI NICE   SIZE    RES STATE    TIME   WCPU
>>>> COMMAND 719 _dhcp       1 129    0  1384K  1092K RUN      2:14
>>>> 93.55% dhclient 607 root        1  98    0 34584K 21212K select  
>>>> 0:09  1.81% Xorg 663 wb          4  20    0 46712K 40224K kserel  
>>>> 0:27  0.00% mozilla-bin 503 root        1   8    0  1184K   796K
>>>> nanslp   0:07  0.00% powerd
>>>>
>>>> Took (best guess) approx 5-10 minutes for the effect to kick in.
>>>
>>>
>>> FYI, I have the same issues with bge(4) and ndis(4).
>>
>>
>>
>> I've seen it on ath and em interfaces now, but am not sure what's going
>> on. and have no idea how to reproduce the problem.  As also reported by
>> Bakul Shah, we seem to be getting into a state where receive_packet() is
>> spinning.  I'm not seeing an obvious way for this to be possible.
> 
> 
> It's the latest change to tables.c that breaks it.  Reverting that 
> single line back, fixes it.

Sigh.. It ran for about 15 minutes, without problems.  Of course, again, 
as soon as I hit send, I see dhclient start chugging a moment later.  I 
suppose it took longer this time since my CPU is already maxed out doing 
portupgrade.

So, nevermind.  All I know, is that about 2 weeks ago, it worked just 
fine.

Eric



-- 
------------------------------------------------------------------------
Eric Anderson        Sr. Systems Administrator        Centaur Technology
Anything that works is better than anything that doesn't.
------------------------------------------------------------------------
Received on Wed Jul 27 2005 - 11:40:49 UTC

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