linux-kernel - Re: [PATCH v2 25/40] tracing: Add support for dynamic tracepoints

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Date:   Fri, 08 Sep 2017 09:18:27 -0500
From:   Tom Zanussi <tom.zanussi@...ux.intel.com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     tglx@...utronix.de, mhiramat@...nel.org, namhyung@...nel.org,
        vedang.patel@...el.com, bigeasy@...utronix.de,
        joel.opensrc@...il.com, joelaf@...gle.com,
        mathieu.desnoyers@...icios.com, baohong.liu@...el.com,
        linux-kernel@...r.kernel.org, linux-rt-users@...r.kernel.org
Subject: Re: [PATCH v2 25/40] tracing: Add support for dynamic tracepoints

Hi Steve,

On Thu, 2017-09-07 at 18:02 -0400, Steven Rostedt wrote:
> On Tue,  5 Sep 2017 16:57:37 -0500
> Tom Zanussi <tom.zanussi@...ux.intel.com> wrote:
> 
> > The tracepoint infrastructure assumes statically-defined tracepoints
> > and uses static_keys for tracepoint enablement.  In order to define
> > tracepoints on the fly, we need to have a dynamic counterpart.
> 
> Do we?
> 
> I believe the static keys should work just fine if you don't have any
> defined static keys jumps, and they should work as a simple counter.
> 
> Could we do that instead of adding another variable to a structure that
> is defined over a thousand times? Save us 4k of memory.
> 

OK, yeah, makes sense if possible - let me look into that... 

Tom