linux-kernel - Re: [PATCH] tracing/function-branch-tracer: enhancements for the trace output

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Date:	Thu, 27 Nov 2008 16:03:43 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Frédéric Weisbecker <fweisbec@...il.com>
Cc:	Steven Rostedt <rostedt@...dmis.org>,
	Tim Bird <tim.bird@...sony.com>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: [PATCH] tracing/function-branch-tracer: enhancements for the
	trace output


* Frédéric Weisbecker <fweisbec@...il.com> wrote:

> 2008/11/27 Ingo Molnar <mingo@...e.hu>:
> >
> > * Frédéric Weisbecker <fweisbec@...il.com> wrote:
> >
> >> >> >  0)    0.993 us |      }
> >> >> > +0)   11.649 us |    }
> >> >> >  0)             |    do_sync_read() {
> >> >> >  0)             |      sock_aio_read() {
> >> >> >  0)             |        __sock_recvmsg() {
> >> >> >  0)             |          security_socket_recvmsg() {
> >> >> > !0)  100.319 us |            cap_socket_recvmsg();
> >> >> > ---------------------------------------------------------
> >>
> >> I like it before the CPU number. The main purpose would be to scroll
> >> quickly the file and find the overheads. That would be easy if set
> >> as a first character.
> >>
> >> I will set it as a default disabled option.
> >
> > lets keep it default-enabled, ok? It makes sense.
> 
> Ok.
> BTW I understand why it is better to have a "pipe" if there is no time:
> 
>   0)             |    do_sync_read() {
>   0)             |      sock_aio_read() {
>   0)             |        __sock_recvmsg() {
>   0)             |          security_socket_recvmsg() {
> 
> But I don't see why it is necessary to have one just after the time:
> 
> !0)  100.319 us |            cap_socket_recvmsg();
> 
> It appears to me as noise....

if you look at it on a console where you look at code, it all looks 
like a straight line:


  0)             |  sys_read() {
  0)    0.331 us |    fget_light();
  0)             |    vfs_read() {
  0)             |      rw_verify_area() {
  0)             |        security_file_permission() {
  0)    0.306 us |          cap_file_permission();
  0)    0.300 us |          cap_file_permission();
  0)    8.909 us |        }
  0)    0.993 us |      }
  0)   11.649 us |    }
  0)             |    do_sync_read() {
                 .   -------------------------
  0)             ==> [ bash-2794 => cat-1234 ]
                     -------------------------


as if the code to the right was on a sheet of paper.


If i understand you correct, are you suggesting this format:

  0)             |  sys_read() {
  0)    0.331 us      fget_light();
  0)             |    vfs_read() {
  0)             |      rw_verify_area() {
  0)             |        security_file_permission() {
  0)    0.306 us            cap_file_permission();
  0)    0.300 us            cap_file_permission();
  0)    8.909 us          }
  0)    0.993 us        }
  0)   11.649 us      }
  0)             |    do_sync_read() {
                 .   -------------------------
  0)             ==> [ bash-2794 => cat-1234 ]
                     -------------------------

i dont think that looks very good.

	Ingo
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