Date: Wed, 8 Jul 2015 09:19:28 -0400
From: Steven Rostedt <rostedt@goodmis.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Chunyan Zhang <zhang.chunyan@linaro.org>, mingo@redhat.com,
        mathieu.poirier@linaro.org, serge.broslavsky@linaro.org,
        broonie@kernel.org, alexander.shishkin@linux.intel.com,
        zhang.lyra@gmail.com, linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH v3 4/4] trace: Trace log handler for logging into
 STM blocks
Message-ID: <20150708091928.38c7643a@gandalf.local.home>
In-Reply-To: <20150708123148.GF12596@twins.programming.kicks-ass.net>
References: <cover.1436262902.git.zhang.chunyan@linaro.org>
	<a1bde0b882e36eb81579e9fb6d2561bdfaee4c06.1436262902.git.zhang.chunyan@linaro.org>
	<20150708123148.GF12596@twins.programming.kicks-ass.net>
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1449
Lines: 42

On Wed, 8 Jul 2015 14:31:48 +0200
Peter Zijlstra <peterz@infradead.org> wrote:

> On Tue, Jul 07, 2015 at 06:10:43PM +0800, Chunyan Zhang wrote:
> > Add the function 'trace_event_stm_output_##call' for printing events
> > trace log into STM blocks.
> > 
> > This patch also adds a function call at where the events have been
> > committed to ring buffer to export the trace event information to
> > STM blocks.
> 
> So then you have two copies of the data, why that? Would a scheme were
> data either goes to the STM or the regular buffer not make much more
> sense?
> 
> > +++ b/include/trace/perf.h
> > @@ -175,6 +175,7 @@ trace_event_raw_event_##call(void *__data, proto)			\
> >  	{ assign; }							\
> >  									\
> >  	trace_event_buffer_commit(&fbuffer);				\
> > +	trace_event_stm_log(&fbuffer);					\
> 
> This makes every trace event slower.

Of course this could use a jump label.

But I agree, I think a switch to which buffer it should be sent to is
better. I could come up with a way to make the buffer more generic, and
have it switch between where the event is recorded.

-- Steve

> 
> >  }
> >  /*
> >   * The ftrace_test_probe is compiled out, it is only here as a build time check

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/