linux-kernel - Re: [RFC][PATCH 1/3] tracing: Added hardware latency tracer

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Message-ID: <20160805104413.781611b5@gandalf.local.home>
Date:	Fri, 5 Aug 2016 10:44:13 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc:	linux-kernel@...r.kernel.org, linux-rt-users@...r.kernel.org,
	Ingo Molnar <mingo@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Clark Williams <williams@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Jon Masters <jcm@...hat.com>, Daniel Wagner <wagi@...om.org>,
	Carsten Emde <C.Emde@...dl.org>
Subject: Re: [RFC][PATCH 1/3] tracing: Added hardware latency tracer

On Fri, 5 Aug 2016 16:25:21 +0200
Sebastian Andrzej Siewior <bigeasy@...utronix.de> wrote:

> * Steven Rostedt | 2016-08-04 10:57:09 [-0400]:
> 
> >diff --git a/kernel/trace/trace_hwlat.c b/kernel/trace/trace_hwlat.c
> >new file mode 100644
> >index 000000000000..08dfabe4e862
> >--- /dev/null
> >+++ b/kernel/trace/trace_hwlat.c  
> …
> >+/* Macros to encapsulate the time capturing infrastructure */
> >+#define time_type	u64
> >+#define time_get()	trace_clock_local()
> >+#define time_to_us(x)	div_u64(x, 1000)
> >+#define time_sub(a, b)	((a) - (b))
> >+#define init_time(a, b)	(a = b)
> >+#define time_u64(a)	a  
> 
> Do we need a macro for this? In the old code we could choose between
> CONFIG_TRACING but now we don't.
> 

Probably not, I kept it for two reasons. 1) to keep the same logic as
what was in PREEMPT_RT, and 2) in case we can come up with a better
clock.

But it's not that important. Should it be nuked? They do somewhat make
the code easier to read.

-- Steve