Messages in this thread | | | Date | Wed, 09 Jul 2008 12:39:04 -0400 | From | Masami Hiramatsu <> | Subject | Re: [patch 04/15] LTTng instrumentation - irq |
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Mathieu Desnoyers wrote: > 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. > > Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> > CC: Thomas Gleixner <tglx@linutronix.de> > CC: Russell King <rmk+lkml@arm.linux.org.uk> > CC: Masami Hiramatsu <mhiramat@redhat.com> > CC: 'Peter Zijlstra' <peterz@infradead.org> > CC: "Frank Ch. Eigler" <fche@redhat.com> > CC: 'Ingo Molnar' <mingo@elte.hu> > CC: 'Hideo AOKI' <haoki@redhat.com> > CC: Takashi Nishiie <t-nishiie@np.css.fujitsu.com> > CC: 'Steven Rostedt' <rostedt@goodmis.org> > CC: Eduard - Gabriel Munteanu <eduard.munteanu@linux360.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 10:57:33.000000000 -0400 > +++ linux-2.6-lttng/kernel/irq/handle.c 2008-07-09 10:57:35.000000000 -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(); > +
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,
-- Masami Hiramatsu
Software Engineer Hitachi Computer Products (America) Inc. Software Solutions Division
e-mail: mhiramat@redhat.com
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