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

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Date:	Mon, 8 Dec 2008 14:47:49 +0100
From:	"Frédéric Weisbecker" <fweisbec@...il.com>
To:	"Ingo Molnar" <mingo@...e.hu>
Cc:	"Steven Rostedt" <rostedt@...dmis.org>,
	"Peter Zijlstra" <a.p.zijlstra@...llo.nl>,
	"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>:
>
> * Frederic Weisbecker <fweisbec@...il.com> wrote:
>
>> +/* Used during output to find the interrupts entry/exit points */
>> +const char *ftrace_graph_irq_entries[] = {
>> +     "smp_call_function_single_interrupt",
>> +     "xen_call_function_single_interrupt",
>> +     "wrapper_smp_local_timer_interrupt",
>> +     "smp_irq_move_cleanup_interrupt",
>> +     "smp_call_function_interrupt",
>> +     "xen_call_function_interrupt",
>> +     "smp_apic_timer_interrupt",
>> +     "uv_bau_message_interrupt",
>> +     "mce_threshold_interrupt",
>> +     "smp_spurious_interrupt",
>> +     "smp_thermal_interrupt",
>> +     "smp_error_interrupt",
>> +     "do_IRQ",
>> +     NULL
>
> hm, couldnt we move these symbols to a separate section, and then only
> check for [section.start ... section.end] instead of this ugly and slow
> array?
>
> Missing a few annotations initially is no big deal - we wont have
> pretty-print. do_IRQ() and smp_apic_timer_interrupt is what matters most
> in practice. "__irqentry" section annotation or so, which puts them into
> .text.irqentry or so - and then irqentry_start/end are extracted via
> appropriate glue in the arch/x86/kernel/vmlinux* linker script.


I found it a bit ugly too while I wrote it :-(
I like this idea of a section, I will just have to verify if it is
between the start and the end of
it to check if its an irq entry.
But I think that even if the others than do_IRQ and
smp_apic_timer_interrupt are more rare,
they should be annotated for this new section (and it seems there are
new coming interrupts
like smp_perf_counter_interrupt() in perf counter....)... Perhaps
someone would profile them...

Hm?
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