linux-kernel - Re: [PATCH v4 06/37] ring-buffer: Redefine the unimplemented RINGBUF_TYPE_TIME

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Message-ID: <1509983553.27629.2.camel@tzanussi-mobl.amr.corp.intel.com>
Date:   Mon, 06 Nov 2017 09:52:33 -0600
From:   Tom Zanussi <tom.zanussi@...ux.intel.com>
To:     Namhyung Kim <namhyung@...nel.org>
Cc:     rostedt@...dmis.org, tglx@...utronix.de, mhiramat@...nel.org,
        vedang.patel@...el.com, bigeasy@...utronix.de,
        joel.opensrc@...il.com, joelaf@...gle.com,
        mathieu.desnoyers@...icios.com, baohong.liu@...el.com,
        rajvi.jingar@...el.com, julia@...com, linux-kernel@...r.kernel.org,
        linux-rt-users@...r.kernel.org, kernel-team@....com
Subject: Re: [PATCH v4 06/37] ring-buffer: Redefine the unimplemented
 RINGBUF_TYPE_TIME_STAMP

Hi Namhyung,

On Mon, 2017-11-06 at 14:09 +0900, Namhyung Kim wrote:
> Hi Tom,
> 
> On Mon, Oct 30, 2017 at 03:51:48PM -0500, Tom Zanussi wrote:
> > RINGBUF_TYPE_TIME_STAMP is defined but not used, and from what I can
> > gather was reserved for something like an absolute timestamp feature
> > for the ring buffer, if not a complete replacement of the current
> > time_delta scheme.
> > 
> > This code redefines RINGBUF_TYPE_TIME_STAMP to implement absolute time
> > stamps.  Another way to look at it is that it essentially forces
> > extended time_deltas for all events.
> > 
> > The motivation for doing this is to enable time_deltas that aren't
> > dependent on previous events in the ring buffer, making it feasible to
> > use the ring_buffer_event timetamps in a more random-access way, for
> > purposes other than serial event printing.
> > 
> > To set/reset this mode, use tracing_set_timestamp_abs() from the
> > previous interface patch.
> > 
> > Signed-off-by: Tom Zanussi <tom.zanussi@...ux.intel.com>
> > ---
> 
> [SNIP]
> > @@ -2220,13 +2246,16 @@ static void rb_inc_iter(struct ring_buffer_iter *iter)
> >  }
> >  
> >  /* Slow path, do not inline */
> > -static noinline struct ring_buffer_event *
> > +static struct noinline ring_buffer_event *
> 
> struct noinline?  Looks like a mistake..
> 

Yeah, it is, not sure how that could have even happened, sheesh.  Thanks
for pointing it out,

Tom