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/kernel/time.c b/arch/powerpc/kernel/time.c
index 92dc844..d6e88df 100644
--- 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 @@
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 @@
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 @@
irq_exit();
set_irq_regs(old_regs);
+
+ trace_timer_interrupt_exit(regs);
}
void wakeup_decrementer(void)