powerpc: tracing: Add powerpc tracepoints for timer entry and exit

We can monitor the effectiveness of our power management of both the
kernel and hypervisor by probing the timer interrupt. For example, on
this box we see 10.37s timer interrupts on an idle core:

<idle>-0     [010]  3900.671297: timer_interrupt_entry: pt_regs=c0000000ce1e7b10
<idle>-0     [010]  3900.671302: timer_interrupt_exit: pt_regs=c0000000ce1e7b10

<idle>-0     [010]  3911.042963: timer_interrupt_entry: pt_regs=c0000000ce1e7b10
<idle>-0     [010]  3911.042968: timer_interrupt_exit: pt_regs=c0000000ce1e7b10

<idle>-0     [010]  3921.414630: timer_interrupt_entry: pt_regs=c0000000ce1e7b10
<idle>-0     [010]  3921.414635: timer_interrupt_exit: pt_regs=c0000000ce1e7b10

Since we have a 207MHz decrementer it will go negative and fire every 10.37s
even if Linux is completely idle.

Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>

diff --git a/arch/powerpc/include/asm/trace.h b/arch/powerpc/include/asm/trace.h
index 187696da5ae7d5c1dc0776198aeb20daf206caf4..b558c31d409edc2ff31e9846537253283a185e6e 100644 (file)
--- a/arch/powerpc/include/asm/trace.h
+++ b/arch/powerpc/include/asm/trace.h
@@ -42,6 +42,40 @@ TRACE_EVENT(irq_exit,
        TP_printk("pt_regs=%p", __entry->regs)
 );
 
+TRACE_EVENT(timer_interrupt_entry,
+
+       TP_PROTO(struct pt_regs *regs),
+
+       TP_ARGS(regs),
+
+       TP_STRUCT__entry(
+               __field(struct pt_regs *, regs)
+       ),
+
+       TP_fast_assign(
+               __entry->regs = regs;
+       ),
+
+       TP_printk("pt_regs=%p", __entry->regs)
+);
+
+TRACE_EVENT(timer_interrupt_exit,
+
+       TP_PROTO(struct pt_regs *regs),
+
+       TP_ARGS(regs),
+
+       TP_STRUCT__entry(
+               __field(struct pt_regs *, regs)
+       ),
+
+       TP_fast_assign(
+               __entry->regs = regs;
+       ),
+
+       TP_printk("pt_regs=%p", __entry->regs)
+);
+
 #endif /* _TRACE_POWERPC_H */
 
 #undef TRACE_INCLUDE_PATH

diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c
index 92dc844299b65ff5b7d934b14e4e110a6d956547..d6e88df4630c586ddb73e9bab7a7a6fbd246c5c8 100644 (file)
--- a/arch/powerpc/kernel/time.c
+++ b/arch/powerpc/kernel/time.c
@@ -54,6 +54,7 @@
 #include <linux/irq.h>
 #include <linux/delay.h>
 #include <linux/perf_event.h>
+#include <asm/trace.h>
 
 #include <asm/io.h>
 #include <asm/processor.h>
@@ -571,6 +572,8 @@ void timer_interrupt(struct pt_regs * regs)
        struct clock_event_device *evt = &decrementer->event;
        u64 now;
 
+       trace_timer_interrupt_entry(regs);
+
        /* Ensure a positive value is written to the decrementer, or else
         * some CPUs will continuue to take decrementer exceptions */
        set_dec(DECREMENTER_MAX);
@@ -590,6 +593,7 @@ void timer_interrupt(struct pt_regs * regs)
                now = decrementer->next_tb - now;
                if (now <= DECREMENTER_MAX)
                        set_dec((int)now);
+               trace_timer_interrupt_exit(regs);
                return;
        }
        old_regs = set_irq_regs(regs);
@@ -620,6 +624,8 @@ void timer_interrupt(struct pt_regs * regs)
 
        irq_exit();
        set_irq_regs(old_regs);
+
+       trace_timer_interrupt_exit(regs);
 }
 
 void wakeup_decrementer(void)