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Date: Wed, 9 Jul 2008 13:05:57 -0400
From: Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
To: Masami Hiramatsu <mhiramat@...hat.com>
Cc: akpm@...ux-foundation.org, Ingo Molnar <mingo@...e.hu>,
linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
Russell King <rmk+lkml@....linux.org.uk>,
Peter Zijlstra <peterz@...radead.org>,
"Frank Ch. Eigler" <fche@...hat.com>,
Hideo AOKI <haoki@...hat.com>,
Takashi Nishiie <t-nishiie@...css.fujitsu.com>,
Steven Rostedt <rostedt@...dmis.org>,
Eduard - Gabriel Munteanu <eduard.munteanu@...ux360.ro>
Subject: Re: [patch 04/15] LTTng instrumentation - irq (update)
* Masami Hiramatsu (mhiramat@...hat.com) wrote:
>
> Hi Mathieu,
> What would you think tracing return value of irq handlers here?
> like:
> trace_irq_exit(retval);
>
> So, we can check the irq was handled correctly or not.
>
> Thank you,
>
>
Sure, here is the updated patch.
Thanks,
Mathieu
LTTng instrumentation - irq
Instrumentation of IRQ related events : irq, softirq, tasklet entry and exit and
softirq "raise" events.
It allows tracers to perform latency analysis on those various types of
interrupts and to detect interrupts with max/min/avg duration. It helps
detecting driver or hardware problems which cause an ISR to take ages to
execute. It has been shown to be the case with bogus hardware causing an mmio
read to take a few milliseconds.
Those tracepoints are used by LTTng.
About the performance impact of tracepoints (which is comparable to markers),
even without immediate values optimizations, tests done by Hideo Aoki on ia64
show no regression. His test case was using hackbench on a kernel where
scheduler instrumentation (about 5 events in code scheduler code) was added.
See the "Tracepoints" patch header for performance result detail.
Changelog:
- Add retval as irq_exit argument.
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
CC: Thomas Gleixner <tglx@...utronix.de>
CC: Russell King <rmk+lkml@....linux.org.uk>
CC: Masami Hiramatsu <mhiramat@...hat.com>
CC: 'Peter Zijlstra' <peterz@...radead.org>
CC: "Frank Ch. Eigler" <fche@...hat.com>
CC: 'Ingo Molnar' <mingo@...e.hu>
CC: 'Hideo AOKI' <haoki@...hat.com>
CC: Takashi Nishiie <t-nishiie@...css.fujitsu.com>
CC: 'Steven Rostedt' <rostedt@...dmis.org>
CC: Eduard - Gabriel Munteanu <eduard.munteanu@...ux360.ro>
---
kernel/irq-trace.h | 36 ++++++++++++++++++++++++++++++++++++
kernel/irq/handle.c | 6 ++++++
kernel/softirq.c | 8 ++++++++
3 files changed, 50 insertions(+)
Index: linux-2.6-lttng/kernel/irq/handle.c
===================================================================
--- linux-2.6-lttng.orig/kernel/irq/handle.c 2008-07-09 12:36:08.000000000 -0400
+++ linux-2.6-lttng/kernel/irq/handle.c 2008-07-09 12:55:33.000000000 -0400
@@ -15,6 +15,7 @@
#include <linux/random.h>
#include <linux/interrupt.h>
#include <linux/kernel_stat.h>
+#include "../irq-trace.h"
#include "internals.h"
@@ -130,6 +131,9 @@ irqreturn_t handle_IRQ_event(unsigned in
{
irqreturn_t ret, retval = IRQ_NONE;
unsigned int status = 0;
+ struct pt_regs *regs = get_irq_regs();
+
+ trace_irq_entry(irq, regs);
handle_dynamic_tick(action);
@@ -148,6 +152,8 @@ irqreturn_t handle_IRQ_event(unsigned in
add_interrupt_randomness(irq);
local_irq_disable();
+ trace_irq_exit(retval);
+
return retval;
}
Index: linux-2.6-lttng/kernel/softirq.c
===================================================================
--- linux-2.6-lttng.orig/kernel/softirq.c 2008-07-09 12:37:15.000000000 -0400
+++ linux-2.6-lttng/kernel/softirq.c 2008-07-09 12:54:58.000000000 -0400
@@ -21,6 +21,7 @@
#include <linux/rcupdate.h>
#include <linux/smp.h>
#include <linux/tick.h>
+#include "irq-trace.h"
#include <asm/irq.h>
/*
@@ -231,7 +232,9 @@ restart:
do {
if (pending & 1) {
+ trace_irq_softirq_entry(h, softirq_vec);
h->action(h);
+ trace_irq_softirq_exit(h, softirq_vec);
rcu_bh_qsctr_inc(cpu);
}
h++;
@@ -323,6 +326,7 @@ void irq_exit(void)
*/
inline void raise_softirq_irqoff(unsigned int nr)
{
+ trace_irq_softirq_raise(nr);
__raise_softirq_irqoff(nr);
/*
@@ -412,7 +416,9 @@ static void tasklet_action(struct softir
if (!atomic_read(&t->count)) {
if (!test_and_clear_bit(TASKLET_STATE_SCHED, &t->state))
BUG();
+ trace_irq_tasklet_low_entry(t);
t->func(t->data);
+ trace_irq_tasklet_low_exit(t);
tasklet_unlock(t);
continue;
}
@@ -447,7 +453,9 @@ static void tasklet_hi_action(struct sof
if (!atomic_read(&t->count)) {
if (!test_and_clear_bit(TASKLET_STATE_SCHED, &t->state))
BUG();
+ trace_irq_tasklet_high_entry(t);
t->func(t->data);
+ trace_irq_tasklet_high_exit(t);
tasklet_unlock(t);
continue;
}
Index: linux-2.6-lttng/kernel/irq-trace.h
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ linux-2.6-lttng/kernel/irq-trace.h 2008-07-09 12:56:11.000000000 -0400
@@ -0,0 +1,36 @@
+#ifndef _IRQ_TRACE_H
+#define _IRQ_TRACE_H
+
+#include <linux/kdebug.h>
+#include <linux/interrupt.h>
+#include <linux/tracepoint.h>
+
+DEFINE_TRACE(irq_entry,
+ TPPROTO(unsigned int id, struct pt_regs *regs),
+ TPARGS(id, regs));
+DEFINE_TRACE(irq_exit,
+ TPPROTO(irqreturn_t retval),
+ TPARGS(retval));
+DEFINE_TRACE(irq_softirq_entry,
+ TPPROTO(struct softirq_action *h, struct softirq_action *softirq_vec),
+ TPARGS(h, softirq_vec));
+DEFINE_TRACE(irq_softirq_exit,
+ TPPROTO(struct softirq_action *h, struct softirq_action *softirq_vec),
+ TPARGS(h, softirq_vec));
+DEFINE_TRACE(irq_softirq_raise,
+ TPPROTO(unsigned int nr),
+ TPARGS(nr));
+DEFINE_TRACE(irq_tasklet_low_entry,
+ TPPROTO(struct tasklet_struct *t),
+ TPARGS(t));
+DEFINE_TRACE(irq_tasklet_low_exit,
+ TPPROTO(struct tasklet_struct *t),
+ TPARGS(t));
+DEFINE_TRACE(irq_tasklet_high_entry,
+ TPPROTO(struct tasklet_struct *t),
+ TPARGS(t));
+DEFINE_TRACE(irq_tasklet_high_exit,
+ TPPROTO(struct tasklet_struct *t),
+ TPARGS(t));
+
+#endif
--
Mathieu Desnoyers
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68
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