netdev - Re: [RFC PATCH 1/2] netdev: buffer infrastructure to log network driver's information

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Message-ID: <4BBACA1F.9030702@jp.fujitsu.com>
Date:	Tue, 06 Apr 2010 14:43:59 +0900
From:	Koki Sanagi <sanagi.koki@...fujitsu.com>
To:	Neil Horman <nhorman@...driver.com>
CC:	David Miller <davem@...emloft.net>, eric.dumazet@...il.com,
	netdev@...r.kernel.org, izumi.taku@...fujitsu.com,
	kaneshige.kenji@...fujitsu.com, jeffrey.t.kirsher@...el.com,
	jesse.brandeburg@...el.com, bruce.w.allan@...el.com,
	alexander.h.duyck@...el.com, peter.p.waskiewicz.jr@...el.com,
	john.ronciak@...el.com
Subject: Re: [RFC PATCH 1/2] netdev: buffer infrastructure to log network
 driver's information

(2010/04/06 9:10), Neil Horman wrote:
> On Mon, Apr 05, 2010 at 12:31:55PM -0700, David Miller wrote:
>> From: Eric Dumazet<eric.dumazet@...il.com>
>> Date: Mon, 05 Apr 2010 10:42:26 +0200
>>
>>> Le lundi 05 avril 2010 à 15:52 +0900, Koki Sanagi a écrit :
>>>> This patch implements buffer infrastructure under driver/net.
>>>> This buffer records information from network driver.
>>>>
>>>> Signed-off-by: Koki Sanagi<sanagi.koki@...fujitsu.com>
>>>> ---
>>>>    drivers/net/Kconfig     |    8 +
>>>>    drivers/net/Makefile    |    1 +
>>>>    drivers/net/ndrvbuf.c   |  535 +++++++++++++++++++++++++++++++++++++++++++++++
>>>>    include/linux/ndrvbuf.h |   57 +++++
>>>>    4 files changed, 601 insertions(+), 0 deletions(-)
>>>>
>>>
>>> Wow, 600 lines... thats what I call bloat...
>>
>> And we have all sorts of facilities for creating filesystem
>> streams and ring buffers of debug information.
>>
>> You could even hook into 'perf' to log and process these
>> events in probably like 12 lines of code.
>>
> I'm still having a hard time understanding why this approach is preferable to
> the previous approach you took using tracepoints.  Granted you can't get driver
> internal state as easily, but its generic and doesn't do...this.
> Neil
>
>
>

We can get below information with this patch

1. Driver operates normaly or not
2. Tx ring's state

About 1, the preivous approach meets, but about 2, some hooks need in driver
code like this patch. If we get it, it is available to solute "Tx Unit Hung"
message. This message indicates that tx descriptor ring's process is not smooth.
When a countermeasure was taken to system that outputs "Tx Unit Hung" message,
this state information is available to evaluate a countermeasure.
But what you say is true, this patch is not generic.
it may be good to rebase the previous approach to focus on 1.
And it is better to consider separately about 2.


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