linux-kernel - Re: [PATCH] of: introduce event tracepoints for dynamic device

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Date:   Wed, 19 Apr 2017 19:37:40 -0700
From:   Frank Rowand <frowand.list@...il.com>
To:     Tyrel Datwyler <tyreld@...ux.vnet.ibm.com>,
        Steven Rostedt <rostedt@...dmis.org>
Cc:     robh+dt@...nel.org, linuxppc-dev@...ts.ozlabs.org,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
        nfont@...ux.vnet.ibm.com, mpe@...erman.id.au, mingo@...hat.com
Subject: Re: [PATCH] of: introduce event tracepoints for dynamic device_node
 lifecyle

On 04/19/17 11:45, Tyrel Datwyler wrote:
> On 04/18/2017 07:49 PM, Steven Rostedt wrote:
>> On Tue, 18 Apr 2017 18:42:32 -0700
>> Frank Rowand <frowand.list@...il.com> wrote:
>>
>>> And of course the other issue with using tracepoints is the extra space
>>> required to hold the tracepoint info.  With the pr_debug() approach, the
>>> space usage can be easily removed for a production kernel via a config
>>> option.
>>
>> Now if you are saying you want to be able to enable debugging without
>> the tracing infrastructure I would agree. As the tracing infrastructure
>> is large. But I'm working on shrinking it more.
> 
> The primary consumers of OF_DYNAMIC seem to be pseries and powernv where
> we are generally going to see the trace infrastructure enabled by
> default in production.

Another primary consumer will be overlays for ARM expansion boards.  Still
a work in progress.

-Frank

> 
> -Tyrel
> 
>>
>>>
>>> Tracepoints are wonderful technology, but not always the proper tool to
>>> use for debug info.
>>
>> But if you are going to have tracing enabled regardless, adding a few
>> more tracepoints isn't going to make the difference.
>>
>> -- Steve
>>
>>>
>>>> If Rob wants to convert printk() style data to trace data (and I can't
>>>> convince him otherwise) then I will have further comments on this specific
>>>> patch.
>>>>
> 
> .
>