Re: [RFC][PATCH 0/5] NFS: trace points added to mounting path

[Steve Dickson <SteveD at redhat dot com>]

Arnaldo Carvalho de Melo wrote:
> Em Wed, Jan 21, 2009 at 11:39:56AM -0500, Steve Dickson escreveu:
>> K.Prasad wrote:
>>> On Mon, Jan 19, 2009 at 09:27:30AM -0500, Jeff Moyer wrote:
>>>> Greg Banks <gnb@melbourne.sgi.com> writes:
>>>>
>>>>> Steve Dickson wrote:
>>>>>> So the ultimate goal would be to replace all the dprintks with trace points
>>>>>> but still be able to enable them through the rpcdebug command
>>>>> I have a patch which changes the definition of the dprintk() macro (but
>>>>> *not* dprintk() callsites) to allow enabling and disabling individual
>>>>> dprintk() statements through a /proc/ interface.  Would you be
>>>>> interested in that?
>>>> That sounds like duplicated work.  How does it differ from Jason Baron's
>>>> dynamic printk patches (which I believe are now upstream)?
>>>>
>>>> Cheers,
>>>> Jeff
>>> Introducing/converting one of the accepted methods of static
>>> instrumentation - like tracepoints would help more users (whether
>>> in-kernel or otherwise) harness them.
>>>
>>> Steve,
>>> 	Would it help convert the systemtap script (nfs_mount.stp) in
>>> Patch - 5 into a kernel module (perhaps in samples/ directory) to bring
>>> an in-kernel user of these tracepoints?
>> Well nfs_mount.stp was just an example of how to pull the information
>> from the kernel.. I just wanted to complete the loop... but as 
>> Christoph pointed out it probably shouldn't been included in the posting.
>>
>> I'm not sure moving the nfs_mount.stp script into kernel 
>> would make sense. One of the advantages of trace point and system
>> scripts (depending on what is passed up) it allows users to define
>> exactly what they need to see.. 
>>
>> For example, a kernel guy might be interested in a particular bit in a flag 
>> field which would be meaningless to an IT guy. On the other hand, the IT guy 
>> would be interested in the error code. One trace point could supply all the
>> information but different systemtap scripts would be need to show the 
>> desired information.
>>
>> My point being, if we move things down into the kernel, I think we would
>> lose this type of flexibly...
> 
> I suggest you provide an ftrace plugin, just like I'm doing with
> blktrace, see:
> 
> http://lkml.org/lkml/2009/1/20/190
I agree its something I need to look into...

steved.