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 CC: Thomas Gleixner CC: Russell King CC: Masami Hiramatsu CC: 'Peter Zijlstra' CC: "Frank Ch. Eigler" CC: 'Ingo Molnar' CC: 'Hideo AOKI' CC: Takashi Nishiie CC: 'Steven Rostedt' CC: Eduard - Gabriel Munteanu --- 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 #include #include +#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(); + return retval; } Index: linux-2.6-lttng/kernel/softirq.c =================================================================== --- linux-2.6-lttng.orig/kernel/softirq.c 2008-07-09 10:57:33.000000000 -0400 +++ linux-2.6-lttng/kernel/softirq.c 2008-07-09 10:57:35.000000000 -0400 @@ -21,6 +21,7 @@ #include #include #include +#include "irq-trace.h" #include /* @@ -205,7 +206,9 @@ 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++; @@ -297,6 +300,7 @@ void irq_exit(void) */ inline void raise_softirq_irqoff(unsigned int nr) { + trace_irq_softirq_raise(nr); __raise_softirq_irqoff(nr); /* @@ -394,7 +398,9 @@ 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; } @@ -429,7 +435,9 @@ 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 10:57:35.000000000 -0400 @@ -0,0 +1,36 @@ +#ifndef _IRQ_TRACE_H +#define _IRQ_TRACE_H + +#include +#include +#include + +DEFINE_TRACE(irq_entry, + TPPROTO(unsigned int id, struct pt_regs *regs), + TPARGS(id, regs)); +DEFINE_TRACE(irq_exit, + TPPROTO(void), + TPARGS()); +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 Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/