linux-kernel - Re: [RFC PATCH v2] trace: Add trace any kernel object

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Date:   Wed, 27 Oct 2021 00:11:00 +0800
From:   Huan Xie <xiehuan09@...il.com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Masami Hiramatsu <mhiramat@...nel.org>, mingo@...hat.com,
        chenhuacai@...nel.org, linux-kernel@...r.kernel.org,
        Tom Zanussi <zanussi@...nel.org>
Subject: Re: [RFC PATCH v2] trace: Add trace any kernel object

On Tue, Oct 26, 2021 at 11:44 PM Steven Rostedt <rostedt@...dmis.org> wrote:
>
> On Tue, 26 Oct 2021 23:40:03 +0800
> Huan Xie <xiehuan09@...il.com> wrote:
>
> > > > static void trace_object_trigger(struct event_trigger_data *data,
> > > > struct trace_buffer *buffer,  void *rec,
> > > >                    struct ring_buffer_event *event)
> > >
> > >
> > > OK, so let me ask this question. What is it that you want to see?
> >
> > Thanks, I got your point now,  my original idea was to just track the
> > flow of objects.
>
> Well, the current patch set doesn't really show any flow of objects, as it
> only records a value that never changes until the next kprobe is hit, and
> we get that from the kprobe itself.

My original purpose was to track which functions the (struct bio)
passed through for the linux block subsystem.
and which functions the (struct page) passed through for the linux
memory subsystem.  ;-)
and I feel this help will be great for learning and developing the linux kernel.

>
> > >
> > > And let's say I want to monitor that __bi_cnt while functions are being
> > > traced. What would be *really cool*, is to mark that value!
> >
> > This is really cool to  get the change of the value. And is a good
> > feature enhancement.
> >
>
> Right, and this is what I thought the purpose of your patch was! :-)
>
> And why I got really excited about it. So I don't see this as a feature
> enhancement to your patch, but the feature enhancement that your patch can
> give us.
>
> -- Steve

--
JeffXie