[PATCH] perf_events: Enable idle state tracing for pseries (ppc64)

Deepthi Dharwar
2011-06-01T12:36:08Z

Hi,

Please find below a patch, which has perf_events added for pseries (ppc64)
platform in order to emit the trace required for perf timechart.
It essentially enables perf timechart for pseries platfrom to analyse
power savings events like cpuidle states.

Steps to enable and disable the trace;
1) Mount debugfs;
mount -t debugfs none /sys/kernel/debug
2) Then, enable the event using;
echo 1 > /sys/kernel/debug/tracing/events/power/cpu_idle/enable
3) The output of the trace can be seen in /sys/kernel/debug/tracing/trace
4) To disable the trace use;
echo 0 > sys/kernel/debug/tracing/events/power/cpu_idle/enable

Trace .svg o/p can be viewed for pseries (ppc64) systems showing various
cpu-idle states as a part of perf timechart tool.
References: http://blog.fenrus.org/?p=5

Issue command 'perf timechart record' to enable tracing.
This generates the trace and records in perf.data file by default.
One can generate output.svg file by issuing 'perf timechart'.

Sample o/p from the trace file:
===============================

State 1 -> Snooze
State 2 -> Cede

# tracer: nop
#
TASK-PID CPU# TIMESTAMP FUNCTION
| | | | |
<idle>-0 [000] 292.482314: cpu_idle: state=1 cpu_id=0
^^ Enter Snooze
<idle>-0 [001] 292.482363: cpu_idle: state=1 cpu_id=1
<idle>-0 [000] 292.492315: cpu_idle: state=4294967295 cpu_id=0
^^ Exit Snooze
<idle>-0 [000] 292.492316: cpu_idle: state=2 cpu_id=0
^^ Enter Cede
<idle>-0 [001] 292.492364: cpu_idle: state=4294967295 cpu_id=1
<idle>-0 [001] 292.492364: cpu_idle: state=2 cpu_id=1
<idle>-0 [000] 292.504198: cpu_idle: state=4294967295 cpu_id=0
^^Exit Cede
<idle>-0 [000] 292.504204: cpu_idle: state=1 cpu_id=0
<idle>-0 [001] 292.504921: cpu_idle: state=4294967295 cpu_id=1
<idle>-0 [001] 292.504936: cpu_idle: state=1 cpu_id=1
<idle>-0 [000] 292.514205: cpu_idle: state=4294967295 cpu_id=0

This patch applies on 2.6.39 and tested on a IBM POWER7 machine.

-Deepthi

Adding perf events to trace various cpu idle states on ppc64 (pseries) platform.
Signed-off-by: Deepthi Dharwar <deepthi@linux.vnet.ibm.com>

pseries.h | 4 ++++
setup.c | 14 ++++++++++++++
2 files changed, 18 insertions(+)

Index: linux-2.6.39/arch/powerpc/platforms/pseries/setup.c
===================================================================
--- linux-2.6.39.orig/arch/powerpc/platforms/pseries/setup.c 2011-05-19 00:06:34.000000000 -0400
+++ linux-2.6.39/arch/powerpc/platforms/pseries/setup.c 2011-06-01 07:46:00.000000000 -0400
@@ -39,6 +39,7 @@
#include <linux/irq.h>
#include <linux/seq_file.h>
#include <linux/root_dev.h>
+#include <trace/events/power.h>

#include <asm/mmu.h>
#include <asm/processor.h>
@@ -582,6 +583,10 @@
* while, do so.
*/
if (snooze) {
+
+ trace_power_start(POWER_CSTATE, CPU_IDLE_SNOOZE, cpu);
+ trace_cpu_idle(CPU_IDLE_SNOOZE, cpu);
+
start_snooze = get_tb() + snooze * tb_ticks_per_usec;
local_irq_enable();
set_thread_flag(TIF_POLLING_NRFLAG);
@@ -602,9 +607,19 @@
goto out;
}

+ trace_power_end(cpu);
+ trace_cpu_idle(PWR_EVENT_EXIT, cpu);
+
+ trace_power_start(POWER_CSTATE, CPU_IDLE_CEDE, cpu);
+ trace_cpu_idle(CPU_IDLE_CEDE, cpu);
+
cede_processor();

out:
+
+ trace_power_end(cpu);
+ trace_cpu_idle(PWR_EVENT_EXIT, cpu);
+
HMT_medium();
out_purr = mfspr(SPRN_PURR);
get_lppaca()->wait_state_cycles += out_purr - in_purr;
Index: linux-2.6.39/arch/powerpc/platforms/pseries/pseries.h
===================================================================
--- linux-2.6.39.orig/arch/powerpc/platforms/pseries/pseries.h 2011-05-19 00:06:34.000000000 -0400
+++ linux-2.6.39/arch/powerpc/platforms/pseries/pseries.h 2011-06-01 07:53:24.000000000 -0400
@@ -12,6 +12,9 @@

#include <linux/interrupt.h>

+#define CPU_IDLE_SNOOZE 1
+#define CPU_IDLE_CEDE 2
+
struct device_node;

extern void request_event_sources_irqs(struct device_node *np,
@@ -56,4 +59,5 @@
extern int dlpar_attach_node(struct device_node *);
extern int dlpar_detach_node(struct device_node *);

+
#endif /* _PSERIES_PSERIES_H */