netdev - Re: KS8695: possible NAPI issue

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Date:	Fri, 5 Mar 2010 11:06:48 +0100
From:	Yegor Yefremov <yegorslists@...glemail.com>
To:	figo zhang <figo1802@...il.com>
Cc:	Dick Hollenbeck <dick@...tplc.com>, netdev@...r.kernel.org,
	zealcook@...il.com
Subject: Re: KS8695: possible NAPI issue

On Fri, Mar 5, 2010 at 7:54 AM, figo zhang <figo1802@...il.com> wrote:
> 2010/3/4 Yegor Yefremov <yegorslists@...glemail.com>:
>>>>> I'm using 2.6.33 kernel and I noticed such a strange behavior:
>>>>>
>>>>> after system start I transfer one file via netcat from my development
>>>>> host, after this transfer the network is not functioning i.e. no pings
>>>>> possible etc.
>>>>>
>>>>> To narrow down the problem I checked out this commit
>>>>>
>>>>> http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=451f14439847db302e5104c44458b2dbb4b1829d.
>>>>> Till here the network driver is functioning as intended, but after
>>>>> NAPI introduction I have this issue. With latest git-pull of "Linus'
>>>>> kernel tree" I can't even ping right after the systems start.
>>>>>
>>>>> Any Ideas? What am I missing?
>>>>>
>>>>
>>>> No idea, although I am using the same ARM chip, my kernel is at 2.6.30.5,
>>>> and except for this occasional loss of connection I get, the ethernet driver
>>>> seems to work better than what you are reporting.
>>>
>>> from linux-2.6.32, this ethernet  driver have add NAPI support, would
>>> you like to
>>> try using this version?
>>
>> Figo, I just looked at the 2.6.32 kernel and found out that it
>> doesn't' contain NAPI support (see the history
>> http://git.kernel.org/?p=linux/kernel/git/stable/linux-2.6.32.y.git;a=history;f=drivers/net/arm/ks8695net.c;h=2a7b7745cc55b54cefada690b0ea47865b54b6b9;hb=HEAD).
>> So 2.6.33 is the first stable kernel to support NAPI.
>>
>> I made some further tests but I can't find the reason for network
>> failures: the interrupts are coming and the packets will be received
>> and sent so that rx/tx counters would be increased, but none of them
>> seem to reach the IP stack. I don't know where and why the things get
>> desynchronized.
>>
>> Could you try the 2.6.33 or Linus tree? Thank you in advance.
>
> yes, i have test it on linux-2.6.33, it is work well.

Thanks for testing. What kind of tests have you made? And with what data amount?

My tests look like following:

1. system start
2. ping one host: O.K.
3. nc -l -p 5000 > /var/test (about 1Mb): O.K.
4. ping the same host: failed

and even if the fourth test succeeds, if I then send a file from other
host the next ping or any other communication fails. I just tried to
make some SSH sessions. It goes without a problem till I issue a ping
after that.

If I test the system with nuttcp I have no problem.

Do you have any idea how to debug this? If I remove the NAPI support I
have no problem with the same kernel and environment. I'd really like
to get the whole stuff working.

Regards,
Yegor
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