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 <[email protected]> --- 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
