linux-kernel - Re: [PATCH 1/2] tracing/function-graph-tracer: signal interrupts entry/exit points on outpout

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Date:	Mon, 08 Dec 2008 07:19:32 +0100
From:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	Frederic Weisbecker <fweisbec@...il.com>
Cc:	Ingo Molnar <mingo@...e.hu>, Steven Rostedt <rostedt@...dmis.org>,
	Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] tracing/function-graph-tracer: signal interrupts
 entry/exit points on outpout

On Mon, 2008-12-08 at 01:54 +0100, Frederic Weisbecker wrote:
> Impact: provide interrupt detection on output
> 
> Suggested by Ingo.
> If a hardirq is raised, we want it to be signaled on output, so this patch
> adds two arrows on the output to find entry and exit points of a hardirq.
> 
> Unfortunately, there are many interrupt entrypoints and these can be differents
> from one arch to another.
> 
> The approach here is one of the easiest, but doesn't shine by its scalability:
> we have an array of the interrupt entrypoints names that we compare with the
> symbol of the current traced function, if it matches, we draw the arrow.
> 
> Ie:
> 
>  1)               |                                unlock_buffer() {
>  1)               |                                  wake_up_bit() {
>  1)               |                                    bit_waitqueue() {
>  1)   0.872 us    |                                      __phys_addr();
>  1)   2.722 us    |                                    }
>  1)               |                                    __wake_up_bit() {
>  1)              ==>                                   __wake_up_bit() {
>  1)               |                                      do_IRQ() {

Would be much nicer, the current proposal is lost when grepping and adds
a weird visual break in the output.

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