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

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Message-ID: <c62985530812080551r10759du97e5fc21a1ac4f9e@mail.gmail.com>
Date:	Mon, 8 Dec 2008 14:51:05 +0100
From:	"Frédéric Weisbecker" <fweisbec@...il.com>
To:	"Ingo Molnar" <mingo@...e.hu>
Cc:	"Peter Zijlstra" <a.p.zijlstra@...llo.nl>,
	"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

2008/12/8 Ingo Molnar <mingo@...e.hu>:
>
> * Frédéric Weisbecker <fweisbec@...il.com> wrote:
>
>> 2008/12/8 Peter Zijlstra <a.p.zijlstra@...llo.nl>:
>> > 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.
>>
>>
>> Ok, I will apply it like this in the V2.
>> Thanks!
>
> note that since the IRQ marker always comes on an entry record, there's
> space in the usecs field for something like:
>
>  1)   2.722 us    |                                    }
>  1)               |                                    __wake_up_bit() {
>  1)  [IRQ#123]   ==>                                   __wake_up_bit() {
>
> right?


Heh, I wanted to display the irq number inside the arrow but didn't
think someone would find it useful.
Ok, will apply that too :-)
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