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Subject[PATCH 1/2] cpu/hotplug: Add cpuhp_latency trace event
Date
Add ftrace event trace_cpuhp_latency to track cpu
hotplug latency. It helps to track the hotplug latency
impact by firmware changes and kernel cpu hotplug callbacks.

Signed-off-by: Prasad Sodagudi <psodagud@codeaurora.org>
---
include/trace/events/cpuhp.h | 29 +++++++++++++++++++++++++++++
kernel/cpu.c | 9 +++++++++
2 files changed, 38 insertions(+)

diff --git a/include/trace/events/cpuhp.h b/include/trace/events/cpuhp.h
index ad16f77..c871850 100644
--- a/include/trace/events/cpuhp.h
+++ b/include/trace/events/cpuhp.h
@@ -6,6 +6,7 @@
#define _TRACE_CPUHP_H

#include <linux/tracepoint.h>
+#include <linux/sched/clock.h>

TRACE_EVENT(cpuhp_enter,

@@ -89,6 +90,34 @@ TRACE_EVENT(cpuhp_exit,
__entry->cpu, __entry->state, __entry->idx, __entry->ret)
);

+TRACE_EVENT(cpuhp_latency,
+
+ TP_PROTO(unsigned int cpu, unsigned int state,
+ u64 start_time, int ret),
+
+ TP_ARGS(cpu, state, start_time, ret),
+
+ TP_STRUCT__entry(
+ __field(unsigned int, cpu)
+ __field(unsigned int, state)
+ __field(u64, time)
+ __field(int, ret)
+ ),
+
+ TP_fast_assign(
+ __entry->cpu = cpu;
+ __entry->state = state;
+ __entry->time = div64_u64(sched_clock() - start_time, 1000);
+ __entry->ret = ret;
+ ),
+
+ TP_printk(" cpu:%d state:%s latency:%llu USEC ret: %d",
+ __entry->cpu, __entry->state ? "online" : "offline",
+ __entry->time, __entry->ret)
+);
+
+
+
#endif

/* This part must be outside protection */
diff --git a/kernel/cpu.c b/kernel/cpu.c
index 6ff2578..68b3740 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -36,6 +36,7 @@
#include <trace/events/power.h>
#define CREATE_TRACE_POINTS
#include <trace/events/cpuhp.h>
+#include <linux/sched/clock.h>

#include "smpboot.h"

@@ -994,6 +995,7 @@ static int __ref _cpu_down(unsigned int cpu, int tasks_frozen,
{
struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
int prev_state, ret = 0;
+ u64 start_time = 0;

if (num_online_cpus() == 1)
return -EBUSY;
@@ -1002,6 +1004,8 @@ static int __ref _cpu_down(unsigned int cpu, int tasks_frozen,
return -EINVAL;

cpus_write_lock();
+ if (trace_cpuhp_latency_enabled())
+ start_time = sched_clock();

cpuhp_tasks_frozen = tasks_frozen;

@@ -1040,6 +1044,7 @@ static int __ref _cpu_down(unsigned int cpu, int tasks_frozen,
}

out:
+ trace_cpuhp_latency(cpu, 0, start_time, ret);
cpus_write_unlock();
/*
* Do post unplug cleanup. This is still protected against
@@ -1192,8 +1197,11 @@ static int _cpu_up(unsigned int cpu, int tasks_frozen, enum cpuhp_state target)
struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
struct task_struct *idle;
int ret = 0;
+ u64 start_time = 0;

cpus_write_lock();
+ if (trace_cpuhp_latency_enabled())
+ start_time = sched_clock();

if (!cpu_present(cpu)) {
ret = -EINVAL;
@@ -1241,6 +1249,7 @@ static int _cpu_up(unsigned int cpu, int tasks_frozen, enum cpuhp_state target)
target = min((int)target, CPUHP_BRINGUP_CPU);
ret = cpuhp_up_callbacks(cpu, st, target);
out:
+ trace_cpuhp_latency(cpu, 1, start_time, ret);
cpus_write_unlock();
arch_smt_update();
return ret;
--
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project
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