Messages in this thread Patch in this message | | | From | Binoy Jayan <> | Subject | [PATCH v5 4/4] tracing: Histogram for delayed hrtimer offsets | Date | Fri, 2 Sep 2016 18:07:31 +0530 |
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Generate a histogram of the latencies of delayed timer offsets in nanoseconds. It shows the latency captured due to a delayed timer expire event. It happens for example when a timer misses its deadline due to disabled interrupts. A process if scheduled as a result of the timer expiration suffers this latency.
The following filter(s) may be used
'hist:key=common_pid.execname:val=toffset,hitcount' 'hist:key=cpu,tcomm:val=toffset:sort=tcomm' 'hist:key=common_pid.execname,tcomm'
Signed-off-by: Binoy Jayan <binoy.jayan@linaro.org> --- include/linux/hrtimer.h | 3 +++ include/trace/events/latency.h | 23 +++++++++++++++++++++ kernel/time/hrtimer.c | 46 ++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 72 insertions(+)
diff --git a/include/linux/hrtimer.h b/include/linux/hrtimer.h index 5e00f80..e09de14 100644 --- a/include/linux/hrtimer.h +++ b/include/linux/hrtimer.h @@ -104,6 +104,9 @@ struct hrtimer { struct hrtimer_clock_base *base; u8 state; u8 is_rel; +#if defined(CONFIG_PREEMPT_TRACER) || defined(CONFIG_IRQSOFF_TRACER) + ktime_t praecox; +#endif #ifdef CONFIG_TIMER_STATS int start_pid; void *start_site; diff --git a/include/trace/events/latency.h b/include/trace/events/latency.h index ca57f06..d616db5 100644 --- a/include/trace/events/latency.h +++ b/include/trace/events/latency.h @@ -44,6 +44,29 @@ DEFINE_EVENT(latency_template, latency_preempt, TP_PROTO(int ltype, cycles_t latency), TP_ARGS(ltype, latency)); +TRACE_EVENT(latency_hrtimer_interrupt, + + TP_PROTO(long long toffset, struct task_struct *task), + + TP_ARGS(toffset, task), + + TP_STRUCT__entry( + __field(long long, toffset) + __array(char, tcomm, TASK_COMM_LEN) + __field(int, tprio) + ), + + TP_fast_assign( + __entry->toffset = toffset; + memcpy(__entry->tcomm, task != NULL ? task->comm : "<none>", + task != NULL ? TASK_COMM_LEN : 7); + __entry->tprio = task != NULL ? task->prio : -1; + ), + + TP_printk("toffset=%lld thread=%s[%d]", + __entry->toffset, __entry->tcomm, __entry->tprio) +); + #endif /* _TRACE_HIST_H */ /* This part must be outside protection */ diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c index 9ba7c82..04d936b 100644 --- a/kernel/time/hrtimer.c +++ b/kernel/time/hrtimer.c @@ -53,9 +53,12 @@ #include <asm/uaccess.h> #include <trace/events/timer.h> +#include <trace/events/latency.h> #include "tick-internal.h" +static enum hrtimer_restart hrtimer_wakeup(struct hrtimer *timer); + /* * The timer bases: * @@ -960,6 +963,45 @@ static inline ktime_t hrtimer_update_lowres(struct hrtimer *timer, ktime_t tim, return tim; } +static inline void latency_hrtimer_timing_start(struct hrtimer *timer, + struct hrtimer_clock_base *new_base, + ktime_t tim) +{ +#if defined(CONFIG_PREEMPT_TRACER) || defined(CONFIG_IRQSOFF_TRACER) + if (unlikely(trace_latency_hrtimer_interrupt_enabled())) { + ktime_t now = new_base->get_time(); + + if (ktime_to_ns(tim) < ktime_to_ns(now)) + timer->praecox = now; + else + timer->praecox = ktime_set(0, 0); + } +#endif +} + +static inline void latency_hrtimer_timing_stop(struct hrtimer *timer, + ktime_t basenow) +{ +#if defined(CONFIG_PREEMPT_TRACER) || defined(CONFIG_IRQSOFF_TRACER) + long latency; + + struct task_struct *task; + + if (likely(!trace_latency_hrtimer_interrupt_enabled())) + return; + + latency = ktime_to_ns(ktime_sub(basenow, + ktime_to_ns(timer->praecox) ? + timer->praecox : hrtimer_get_expires(timer))); + + task = timer->function == hrtimer_wakeup ? + container_of(timer, struct hrtimer_sleeper, + timer)->task : NULL; + if (latency > 0) + trace_latency_hrtimer_interrupt((u64) latency, task); +#endif +} + /** * hrtimer_start_range_ns - (re)start an hrtimer on the current CPU * @timer: the timer to be added @@ -992,6 +1034,8 @@ void hrtimer_start_range_ns(struct hrtimer *timer, ktime_t tim, timer_stats_hrtimer_set_start_info(timer); + latency_hrtimer_timing_start(timer, new_base, tim); + leftmost = enqueue_hrtimer(timer, new_base); if (!leftmost) goto unlock; @@ -1284,6 +1328,8 @@ static void __hrtimer_run_queues(struct hrtimer_cpu_base *cpu_base, ktime_t now) timer = container_of(node, struct hrtimer, node); + latency_hrtimer_timing_stop(timer, basenow); + /* * The immediate goal for using the softexpires is * minimizing wakeups, not running timers at the -- The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project
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