diff options
Diffstat (limited to 'kernel/trace/trace_osnoise.c')
| -rw-r--r-- | kernel/trace/trace_osnoise.c | 2059 |
1 files changed, 2059 insertions, 0 deletions
diff --git a/kernel/trace/trace_osnoise.c b/kernel/trace/trace_osnoise.c new file mode 100644 index 000000000000..a7e3c24dee13 --- /dev/null +++ b/kernel/trace/trace_osnoise.c @@ -0,0 +1,2059 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * OS Noise Tracer: computes the OS Noise suffered by a running thread. + * Timerlat Tracer: measures the wakeup latency of a timer triggered IRQ and thread. + * + * Based on "hwlat_detector" tracer by: + * Copyright (C) 2008-2009 Jon Masters, Red Hat, Inc. <jcm@redhat.com> + * Copyright (C) 2013-2016 Steven Rostedt, Red Hat, Inc. <srostedt@redhat.com> + * With feedback from Clark Williams <williams@redhat.com> + * + * And also based on the rtsl tracer presented on: + * DE OLIVEIRA, Daniel Bristot, et al. Demystifying the real-time linux + * scheduling latency. In: 32nd Euromicro Conference on Real-Time Systems + * (ECRTS 2020). Schloss Dagstuhl-Leibniz-Zentrum fur Informatik, 2020. + * + * Copyright (C) 2021 Daniel Bristot de Oliveira, Red Hat, Inc. <bristot@redhat.com> + */ + +#include <linux/kthread.h> +#include <linux/tracefs.h> +#include <linux/uaccess.h> +#include <linux/cpumask.h> +#include <linux/delay.h> +#include <linux/sched/clock.h> +#include <uapi/linux/sched/types.h> +#include <linux/sched.h> +#include "trace.h" + +#ifdef CONFIG_X86_LOCAL_APIC +#include <asm/trace/irq_vectors.h> +#undef TRACE_INCLUDE_PATH +#undef TRACE_INCLUDE_FILE +#endif /* CONFIG_X86_LOCAL_APIC */ + +#include <trace/events/irq.h> +#include <trace/events/sched.h> + +#define CREATE_TRACE_POINTS +#include <trace/events/osnoise.h> + +static struct trace_array *osnoise_trace; + +/* + * Default values. + */ +#define BANNER "osnoise: " +#define DEFAULT_SAMPLE_PERIOD 1000000 /* 1s */ +#define DEFAULT_SAMPLE_RUNTIME 1000000 /* 1s */ + +#define DEFAULT_TIMERLAT_PERIOD 1000 /* 1ms */ +#define DEFAULT_TIMERLAT_PRIO 95 /* FIFO 95 */ + +/* + * NMI runtime info. + */ +struct osn_nmi { + u64 count; + u64 delta_start; +}; + +/* + * IRQ runtime info. + */ +struct osn_irq { + u64 count; + u64 arrival_time; + u64 delta_start; +}; + +#define IRQ_CONTEXT 0 +#define THREAD_CONTEXT 1 +/* + * sofirq runtime info. + */ +struct osn_softirq { + u64 count; + u64 arrival_time; + u64 delta_start; +}; + +/* + * thread runtime info. + */ +struct osn_thread { + u64 count; + u64 arrival_time; + u64 delta_start; +}; + +/* + * Runtime information: this structure saves the runtime information used by + * one sampling thread. + */ +struct osnoise_variables { + struct task_struct *kthread; + bool sampling; + pid_t pid; + struct osn_nmi nmi; + struct osn_irq irq; + struct osn_softirq softirq; + struct osn_thread thread; + local_t int_counter; +}; + +/* + * Per-cpu runtime information. + */ +DEFINE_PER_CPU(struct osnoise_variables, per_cpu_osnoise_var); + +/* + * this_cpu_osn_var - Return the per-cpu osnoise_variables on its relative CPU + */ +static inline struct osnoise_variables *this_cpu_osn_var(void) +{ + return this_cpu_ptr(&per_cpu_osnoise_var); +} + +#ifdef CONFIG_TIMERLAT_TRACER +/* + * Runtime information for the timer mode. + */ +struct timerlat_variables { + struct task_struct *kthread; + struct hrtimer timer; + u64 rel_period; + u64 abs_period; + bool tracing_thread; + u64 count; +}; + +DEFINE_PER_CPU(struct timerlat_variables, per_cpu_timerlat_var); + +/* + * this_cpu_tmr_var - Return the per-cpu timerlat_variables on its relative CPU + */ +static inline struct timerlat_variables *this_cpu_tmr_var(void) +{ + return this_cpu_ptr(&per_cpu_timerlat_var); +} + +/* + * tlat_var_reset - Reset the values of the given timerlat_variables + */ +static inline void tlat_var_reset(void) +{ + struct timerlat_variables *tlat_var; + int cpu; + /* + * So far, all the values are initialized as 0, so + * zeroing the structure is perfect. + */ + for_each_cpu(cpu, cpu_online_mask) { + tlat_var = per_cpu_ptr(&per_cpu_timerlat_var, cpu); + memset(tlat_var, 0, sizeof(*tlat_var)); + } +} +#else /* CONFIG_TIMERLAT_TRACER */ +#define tlat_var_reset() do {} while (0) +#endif /* CONFIG_TIMERLAT_TRACER */ + +/* + * osn_var_reset - Reset the values of the given osnoise_variables + */ +static inline void osn_var_reset(void) +{ + struct osnoise_variables *osn_var; + int cpu; + + /* + * So far, all the values are initialized as 0, so + * zeroing the structure is perfect. + */ + for_each_cpu(cpu, cpu_online_mask) { + osn_var = per_cpu_ptr(&per_cpu_osnoise_var, cpu); + memset(osn_var, 0, sizeof(*osn_var)); + } +} + +/* + * osn_var_reset_all - Reset the value of all per-cpu osnoise_variables + */ +static inline void osn_var_reset_all(void) +{ + osn_var_reset(); + tlat_var_reset(); +} + +/* + * Tells NMIs to call back to the osnoise tracer to record timestamps. + */ +bool trace_osnoise_callback_enabled; + +/* + * osnoise sample structure definition. Used to store the statistics of a + * sample run. + */ +struct osnoise_sample { + u64 runtime; /* runtime */ + u64 noise; /* noise */ + u64 max_sample; /* max single noise sample */ + int hw_count; /* # HW (incl. hypervisor) interference */ + int nmi_count; /* # NMIs during this sample */ + int irq_count; /* # IRQs during this sample */ + int softirq_count; /* # softirqs during this sample */ + int thread_count; /* # threads during this sample */ +}; + +#ifdef CONFIG_TIMERLAT_TRACER +/* + * timerlat sample structure definition. Used to store the statistics of + * a sample run. + */ +struct timerlat_sample { + u64 timer_latency; /* timer_latency */ + unsigned int seqnum; /* unique sequence */ + int context; /* timer context */ +}; +#endif + +/* + * Protect the interface. + */ +struct mutex interface_lock; + +/* + * Tracer data. + */ +static struct osnoise_data { + u64 sample_period; /* total sampling period */ + u64 sample_runtime; /* active sampling portion of period */ + u64 stop_tracing; /* stop trace in the internal operation (loop/irq) */ + u64 stop_tracing_total; /* stop trace in the final operation (report/thread) */ +#ifdef CONFIG_TIMERLAT_TRACER + u64 timerlat_period; /* timerlat period */ + u64 print_stack; /* print IRQ stack if total > */ + int timerlat_tracer; /* timerlat tracer */ +#endif + bool tainted; /* infor users and developers about a problem */ +} osnoise_data = { + .sample_period = DEFAULT_SAMPLE_PERIOD, + .sample_runtime = DEFAULT_SAMPLE_RUNTIME, + .stop_tracing = 0, + .stop_tracing_total = 0, +#ifdef CONFIG_TIMERLAT_TRACER + .print_stack = 0, + .timerlat_period = DEFAULT_TIMERLAT_PERIOD, + .timerlat_tracer = 0, +#endif +}; + +/* + * Boolean variable used to inform that the tracer is currently sampling. + */ +static bool osnoise_busy; + +/* + * Print the osnoise header info. + */ +static void print_osnoise_headers(struct seq_file *s) +{ + if (osnoise_data.tainted) + seq_puts(s, "# osnoise is tainted!\n"); + + seq_puts(s, "# _-----=> irqs-off\n"); + seq_puts(s, "# / _----=> need-resched\n"); + seq_puts(s, "# | / _---=> hardirq/softirq\n"); + seq_puts(s, "# || / _--=> preempt-depth "); + seq_puts(s, " MAX\n"); + + seq_puts(s, "# || / "); + seq_puts(s, " SINGLE Interference counters:\n"); + + seq_puts(s, "# |||| RUNTIME "); + seq_puts(s, " NOISE %% OF CPU NOISE +-----------------------------+\n"); + + seq_puts(s, "# TASK-PID CPU# |||| TIMESTAMP IN US "); + seq_puts(s, " IN US AVAILABLE IN US HW NMI IRQ SIRQ THREAD\n"); + + seq_puts(s, "# | | | |||| | | "); + seq_puts(s, " | | | | | | | |\n"); +} + +/* + * osnoise_taint - report an osnoise error. + */ +#define osnoise_taint(msg) ({ \ + struct trace_array *tr = osnoise_trace; \ + \ + trace_array_printk_buf(tr->array_buffer.buffer, _THIS_IP_, msg); \ + osnoise_data.tainted = true; \ +}) + +/* + * Record an osnoise_sample into the tracer buffer. + */ +static void trace_osnoise_sample(struct osnoise_sample *sample) +{ + struct trace_array *tr = osnoise_trace; + struct trace_buffer *buffer = tr->array_buffer.buffer; + struct trace_event_call *call = &event_osnoise; + struct ring_buffer_event *event; + struct osnoise_entry *entry; + + event = trace_buffer_lock_reserve(buffer, TRACE_OSNOISE, sizeof(*entry), + tracing_gen_ctx()); + if (!event) + return; + entry = ring_buffer_event_data(event); + entry->runtime = sample->runtime; + entry->noise = sample->noise; + entry->max_sample = sample->max_sample; + entry->hw_count = sample->hw_count; + entry->nmi_count = sample->nmi_count; + entry->irq_count = sample->irq_count; + entry->softirq_count = sample->softirq_count; + entry->thread_count = sample->thread_count; + + if (!call_filter_check_discard(call, entry, buffer, event)) + trace_buffer_unlock_commit_nostack(buffer, event); +} + +#ifdef CONFIG_TIMERLAT_TRACER +/* + * Print the timerlat header info. + */ +static void print_timerlat_headers(struct seq_file *s) +{ + seq_puts(s, "# _-----=> irqs-off\n"); + seq_puts(s, "# / _----=> need-resched\n"); + seq_puts(s, "# | / _---=> hardirq/softirq\n"); + seq_puts(s, "# || / _--=> preempt-depth\n"); + seq_puts(s, "# || /\n"); + seq_puts(s, "# |||| ACTIVATION\n"); + seq_puts(s, "# TASK-PID CPU# |||| TIMESTAMP ID "); + seq_puts(s, " CONTEXT LATENCY\n"); + seq_puts(s, "# | | | |||| | | "); + seq_puts(s, " | |\n"); +} + +/* + * Record an timerlat_sample into the tracer buffer. + */ +static void trace_timerlat_sample(struct timerlat_sample *sample) +{ + struct trace_array *tr = osnoise_trace; + struct trace_event_call *call = &event_osnoise; + struct trace_buffer *buffer = tr->array_buffer.buffer; + struct ring_buffer_event *event; + struct timerlat_entry *entry; + + event = trace_buffer_lock_reserve(buffer, TRACE_TIMERLAT, sizeof(*entry), + tracing_gen_ctx()); + if (!event) + return; + entry = ring_buffer_event_data(event); + entry->seqnum = sample->seqnum; + entry->context = sample->context; + entry->timer_latency = sample->timer_latency; + + if (!call_filter_check_discard(call, entry, buffer, event)) + trace_buffer_unlock_commit_nostack(buffer, event); +} + +#ifdef CONFIG_STACKTRACE + +#define MAX_CALLS 256 + +/* + * Stack trace will take place only at IRQ level, so, no need + * to control nesting here. + */ +struct trace_stack { + int stack_size; + int nr_entries; + unsigned long calls[MAX_CALLS]; +}; + +static DEFINE_PER_CPU(struct trace_stack, trace_stack); + +/* + * timerlat_save_stack - save a stack trace without printing + * + * Save the current stack trace without printing. The + * stack will be printed later, after the end of the measurement. + */ +static void timerlat_save_stack(int skip) +{ + unsigned int size, nr_entries; + struct trace_stack *fstack; + + fstack = this_cpu_ptr(&trace_stack); + + size = ARRAY_SIZE(fstack->calls); + + nr_entries = stack_trace_save(fstack->calls, size, skip); + + fstack->stack_size = nr_entries * sizeof(unsigned long); + fstack->nr_entries = nr_entries; + + return; + +} +/* + * timerlat_dump_stack - dump a stack trace previously saved + * + * Dump a saved stack trace into the trace buffer. + */ +static void timerlat_dump_stack(void) +{ + struct trace_event_call *call = &event_osnoise; + struct trace_array *tr = osnoise_trace; + struct trace_buffer *buffer = tr->array_buffer.buffer; + struct ring_buffer_event *event; + struct trace_stack *fstack; + struct stack_entry *entry; + unsigned int size; + + preempt_disable_notrace(); + fstack = this_cpu_ptr(&trace_stack); + size = fstack->stack_size; + + event = trace_buffer_lock_reserve(buffer, TRACE_STACK, sizeof(*entry) + size, + tracing_gen_ctx()); + if (!event) + goto out; + + entry = ring_buffer_event_data(event); + + memcpy(&entry->caller, fstack->calls, size); + entry->size = fstack->nr_entries; + + if (!call_filter_check_discard(call, entry, buffer, event)) + trace_buffer_unlock_commit_nostack(buffer, event); + +out: + preempt_enable_notrace(); +} +#else +#define timerlat_dump_stack() do {} while (0) +#define timerlat_save_stack(a) do {} while (0) +#endif /* CONFIG_STACKTRACE */ +#endif /* CONFIG_TIMERLAT_TRACER */ + +/* + * Macros to encapsulate the time capturing infrastructure. + */ +#define time_get() trace_clock_local() +#define time_to_us(x) div_u64(x, 1000) +#define time_sub(a, b) ((a) - (b)) + +/* + * cond_move_irq_delta_start - Forward the delta_start of a running IRQ + * + * If an IRQ is preempted by an NMI, its delta_start is pushed forward + * to discount the NMI interference. + * + * See get_int_safe_duration(). + */ +static inline void +cond_move_irq_delta_start(struct osnoise_variables *osn_var, u64 duration) +{ + if (osn_var->irq.delta_start) + osn_var->irq.delta_start += duration; +} + +#ifndef CONFIG_PREEMPT_RT +/* + * cond_move_softirq_delta_start - Forward the delta_start of a running softirq. + * + * If a softirq is preempted by an IRQ or NMI, its delta_start is pushed + * forward to discount the interference. + * + * See get_int_safe_duration(). + */ +static inline void +cond_move_softirq_delta_start(struct osnoise_variables *osn_var, u64 duration) +{ + if (osn_var->softirq.delta_start) + osn_var->softirq.delta_start += duration; +} +#else /* CONFIG_PREEMPT_RT */ +#define cond_move_softirq_delta_start(osn_var, duration) do {} while (0) +#endif + +/* + * cond_move_thread_delta_start - Forward the delta_start of a running thread + * + * If a noisy thread is preempted by an softirq, IRQ or NMI, its delta_start + * is pushed forward to discount the interference. + * + * See get_int_safe_duration(). + */ +static inline void +cond_move_thread_delta_start(struct osnoise_variables *osn_var, u64 duration) +{ + if (osn_var->thread.delta_start) + osn_var->thread.delta_start += duration; +} + +/* + * get_int_safe_duration - Get the duration of a window + * + * The irq, softirq and thread varaibles need to have its duration without + * the interference from higher priority interrupts. Instead of keeping a + * variable to discount the interrupt interference from these variables, the + * starting time of these variables are pushed forward with the interrupt's + * duration. In this way, a single variable is used to: + * + * - Know if a given window is being measured. + * - Account its duration. + * - Discount the interference. + * + * To avoid getting inconsistent values, e.g.,: + * + * now = time_get() + * ---> interrupt! + * delta_start -= int duration; + * <--- + * duration = now - delta_start; + * + * result: negative duration if the variable duration before the + * interrupt was smaller than the interrupt execution. + * + * A counter of interrupts is used. If the counter increased, try + * to capture an interference safe duration. + */ +static inline s64 +get_int_safe_duration(struct osnoise_variables *osn_var, u64 *delta_start) +{ + u64 int_counter, now; + s64 duration; + + do { + int_counter = local_read(&osn_var->int_counter); + /* synchronize with interrupts */ + barrier(); + + now = time_get(); + duration = (now - *delta_start); + + /* synchronize with interrupts */ + barrier(); + } while (int_counter != local_read(&osn_var->int_counter)); + + /* + * This is an evidence of race conditions that cause + * a value to be "discounted" too much. + */ + if (duration < 0) + osnoise_taint("Negative duration!\n"); + + *delta_start = 0; + + return duration; +} + +/* + * + * set_int_safe_time - Save the current time on *time, aware of interference + * + * Get the time, taking into consideration a possible interference from + * higher priority interrupts. + * + * See get_int_safe_duration() for an explanation. + */ +static u64 +set_int_safe_time(struct osnoise_variables *osn_var, u64 *time) +{ + u64 int_counter; + + do { + int_counter = local_read(&osn_var->int_counter); + /* synchronize with interrupts */ + barrier(); + + *time = time_get(); + + /* synchronize with interrupts */ + barrier(); + } while (int_counter != local_read(&osn_var->int_counter)); + + return int_counter; +} + +#ifdef CONFIG_TIMERLAT_TRACER +/* + * copy_int_safe_time - Copy *src into *desc aware of interference + */ +static u64 +copy_int_safe_time(struct osnoise_variables *osn_var, u64 *dst, u64 *src) +{ + u64 int_counter; + + do { + int_counter = local_read(&osn_var->int_counter); + /* synchronize with interrupts */ + barrier(); + + *dst = *src; + + /* synchronize with interrupts */ + barrier(); + } while (int_counter != local_read(&osn_var->int_counter)); + + return int_counter; +} +#endif /* CONFIG_TIMERLAT_TRACER */ + +/* + * trace_osnoise_callback - NMI entry/exit callback + * + * This function is called at the entry and exit NMI code. The bool enter + * distinguishes between either case. This function is used to note a NMI + * occurrence, compute the noise caused by the NMI, and to remove the noise + * it is potentially causing on other interference variables. + */ +void trace_osnoise_callback(bool enter) +{ + struct osnoise_variables *osn_var = this_cpu_osn_var(); + u64 duration; + + if (!osn_var->sampling) + return; + + /* + * Currently trace_clock_local() calls sched_clock() and the + * generic version is not NMI safe. + */ + if (!IS_ENABLED(CONFIG_GENERIC_SCHED_CLOCK)) { + if (enter) { + osn_var->nmi.delta_start = time_get(); + local_inc(&osn_var->int_counter); + } else { + duration = time_get() - osn_var->nmi.delta_start; + + trace_nmi_noise(osn_var->nmi.delta_start, duration); + + cond_move_irq_delta_start(osn_var, duration); + cond_move_softirq_delta_start(osn_var, duration); + cond_move_thread_delta_start(osn_var, duration); + } + } + + if (enter) + osn_var->nmi.count++; +} + +/* + * osnoise_trace_irq_entry - Note the starting of an IRQ + * + * Save the starting time of an IRQ. As IRQs are non-preemptive to other IRQs, + * it is safe to use a single variable (ons_var->irq) to save the statistics. + * The arrival_time is used to report... the arrival time. The delta_start + * is used to compute the duration at the IRQ exit handler. See + * cond_move_irq_delta_start(). + */ +void osnoise_trace_irq_entry(int id) +{ + struct osnoise_variables *osn_var = this_cpu_osn_var(); + + if (!osn_var->sampling) + return; + /* + * This value will be used in the report, but not to compute + * the execution time, so it is safe to get it unsafe. + */ + osn_var->irq.arrival_time = time_get(); + set_int_safe_time(osn_var, &osn_var->irq.delta_start); + osn_var->irq.count++; + + local_inc(&osn_var->int_counter); +} + +/* + * osnoise_irq_exit - Note the end of an IRQ, sava data and trace + * + * Computes the duration of the IRQ noise, and trace it. Also discounts the + * interference from other sources of noise could be currently being accounted. + */ +void osnoise_trace_irq_exit(int id, const char *desc) +{ + struct osnoise_variables *osn_var = this_cpu_osn_var(); + int duration; + + if (!osn_var->sampling) + return; + + duration = get_int_safe_duration(osn_var, &osn_var->irq.delta_start); + trace_irq_noise(id, desc, osn_var->irq.arrival_time, duration); + osn_var->irq.arrival_time = 0; + cond_move_softirq_delta_start(osn_var, duration); + cond_move_thread_delta_start(osn_var, duration); +} + +/* + * trace_irqentry_callback - Callback to the irq:irq_entry traceevent + * + * Used to note the starting of an IRQ occurece. + */ +static void trace_irqentry_callback(void *data, int irq, + struct irqaction *action) +{ + osnoise_trace_irq_entry(irq); +} + +/* + * trace_irqexit_callback - Callback to the irq:irq_exit traceevent + * + * Used to note the end of an IRQ occurece. + */ +static void trace_irqexit_callback(void *data, int irq, + struct irqaction *action, int ret) +{ + osnoise_trace_irq_exit(irq, action->name); +} + +/* + * arch specific register function. + */ +int __weak osnoise_arch_register(void) +{ + return 0; +} + +/* + * arch specific unregister function. + */ +void __weak osnoise_arch_unregister(void) +{ + return; +} + +/* + * hook_irq_events - Hook IRQ handling events + * + * This function hooks the IRQ related callbacks to the respective trace + * events. + */ +static int hook_irq_events(void) +{ + int ret; + + ret = register_trace_irq_handler_entry(trace_irqentry_callback, NULL); + if (ret) + goto out_err; + + ret = register_trace_irq_handler_exit(trace_irqexit_callback, NULL); + if (ret) + goto out_unregister_entry; + + ret = osnoise_arch_register(); + if (ret) + goto out_irq_exit; + + return 0; + +out_irq_exit: + unregister_trace_irq_handler_exit(trace_irqexit_callback, NULL); +out_unregister_entry: + unregister_trace_irq_handler_entry(trace_irqentry_callback, NULL); +out_err: + return -EINVAL; +} + +/* + * unhook_irq_events - Unhook IRQ handling events + * + * This function unhooks the IRQ related callbacks to the respective trace + * events. + */ +static void unhook_irq_events(void) +{ + osnoise_arch_unregister(); + unregister_trace_irq_handler_exit(trace_irqexit_callback, NULL); + unregister_trace_irq_handler_entry(trace_irqentry_callback, NULL); +} + +#ifndef CONFIG_PREEMPT_RT +/* + * trace_softirq_entry_callback - Note the starting of a softirq + * + * Save the starting time of a softirq. As softirqs are non-preemptive to + * other softirqs, it is safe to use a single variable (ons_var->softirq) + * to save the statistics. The arrival_time is used to report... the + * arrival time. The delta_start is used to compute the duration at the + * softirq exit handler. See cond_move_softirq_delta_start(). + */ +static void trace_softirq_entry_callback(void *data, unsigned int vec_nr) +{ + struct osnoise_variables *osn_var = this_cpu_osn_var(); + + if (!osn_var->sampling) + return; + /* + * This value will be used in the report, but not to compute + * the execution time, so it is safe to get it unsafe. + */ + osn_var->softirq.arrival_time = time_get(); + set_int_safe_time(osn_var, &osn_var->softirq.delta_start); + osn_var->softirq.count++; + + local_inc(&osn_var->int_counter); +} + +/* + * trace_softirq_exit_callback - Note the end of an softirq + * + * Computes the duration of the softirq noise, and trace it. Also discounts the + * interference from other sources of noise could be currently being accounted. + */ +static void trace_softirq_exit_callback(void *data, unsigned int vec_nr) +{ + struct osnoise_variables *osn_var = this_cpu_osn_var(); + int duration; + + if (!osn_var->sampling) + return; + +#ifdef CONFIG_TIMERLAT_TRACER + /* + * If the timerlat is enabled, but the irq handler did + * not run yet enabling timerlat_tracer, do not trace. + */ + if (unlikely(osnoise_data.timerlat_tracer)) { + struct timerlat_variables *tlat_var; + tlat_var = this_cpu_tmr_var(); + if (!tlat_var->tracing_thread) { + osn_var->softirq.arrival_time = 0; + osn_var->softirq.delta_start = 0; + return; + } + } +#endif + + duration = get_int_safe_duration(osn_var, &osn_var->softirq.delta_start); + trace_softirq_noise(vec_nr, osn_var->softirq.arrival_time, duration); + cond_move_thread_delta_start(osn_var, duration); + osn_var->softirq.arrival_time = 0; +} + +/* + * hook_softirq_events - Hook softirq handling events + * + * This function hooks the softirq related callbacks to the respective trace + * events. + */ +static int hook_softirq_events(void) +{ + int ret; + + ret = register_trace_softirq_entry(trace_softirq_entry_callback, NULL); + if (ret) + goto out_err; + + ret = register_trace_softirq_exit(trace_softirq_exit_callback, NULL); + if (ret) + goto out_unreg_entry; + + return 0; + +out_unreg_entry: + unregister_trace_softirq_entry(trace_softirq_entry_callback, NULL); +out_err: + return -EINVAL; +} + +/* + * unhook_softirq_events - Unhook softirq handling events + * + * This function hooks the softirq related callbacks to the respective trace + * events. + */ +static void unhook_softirq_events(void) +{ + unregister_trace_softirq_entry(trace_softirq_entry_callback, NULL); + unregister_trace_softirq_exit(trace_softirq_exit_callback, NULL); +} +#else /* CONFIG_PREEMPT_RT */ +/* + * softirq are threads on the PREEMPT_RT mode. + */ +static int hook_softirq_events(void) +{ + return 0; +} +static void unhook_softirq_events(void) +{ +} +#endif + +/* + * thread_entry - Record the starting of a thread noise window + * + * It saves the context switch time for a noisy thread, and increments + * the interference counters. + */ +static void +thread_entry(struct osnoise_variables *osn_var, struct task_struct *t) +{ + if (!osn_var->sampling) + return; + /* + * The arrival time will be used in the report, but not to compute + * the execution time, so it is safe to get it unsafe. + */ + osn_var->thread.arrival_time = time_get(); + + set_int_safe_time(osn_var, &osn_var->thread.delta_start); + + osn_var->thread.count++; + local_inc(&osn_var->int_counter); +} + +/* + * thread_exit - Report the end of a thread noise window + * + * It computes the total noise from a thread, tracing if needed. + */ +static void +thread_exit(struct osnoise_variables *osn_var, struct task_struct *t) +{ + int duration; + + if (!osn_var->sampling) + return; + +#ifdef CONFIG_TIMERLAT_TRACER + if (osnoise_data.timerlat_tracer) { + struct timerlat_variables *tlat_var; + tlat_var = this_cpu_tmr_var(); + if (!tlat_var->tracing_thread) { + osn_var->thread.delta_start = 0; + osn_var->thread.arrival_time = 0; + return; + } + } +#endif + + duration = get_int_safe_duration(osn_var, &osn_var->thread.delta_start); + + trace_thread_noise(t, osn_var->thread.arrival_time, duration); + + osn_var->thread.arrival_time = 0; +} + +/* + * trace_sched_switch - sched:sched_switch trace event handler + * + * This function is hooked to the sched:sched_switch trace event, and it is + * used to record the beginning and to report the end of a thread noise window. + */ +static void +trace_sched_switch_callback(void *data, bool preempt, struct task_struct *p, + struct task_struct *n) +{ + struct osnoise_variables *osn_var = this_cpu_osn_var(); + + if (p->pid != osn_var->pid) + thread_exit(osn_var, p); + + if (n->pid != osn_var->pid) + thread_entry(osn_var, n); +} + +/* + * hook_thread_events - Hook the insturmentation for thread noise + * + * Hook the osnoise tracer callbacks to handle the noise from other + * threads on the necessary kernel events. + */ +static int hook_thread_events(void) +{ + int ret; + + ret = register_trace_sched_switch(trace_sched_switch_callback, NULL); + if (ret) + return -EINVAL; + + return 0; +} + +/* + * unhook_thread_events - *nhook the insturmentation for thread noise + * + * Unook the osnoise tracer callbacks to handle the noise from other + * threads on the necessary kernel events. + */ +static void unhook_thread_events(void) +{ + unregister_trace_sched_switch(trace_sched_switch_callback, NULL); +} + +/* + * save_osn_sample_stats - Save the osnoise_sample statistics + * + * Save the osnoise_sample statistics before the sampling phase. These + * values will be used later to compute the diff betwneen the statistics + * before and after the osnoise sampling. + */ +static void +save_osn_sample_stats(struct osnoise_variables *osn_var, struct osnoise_sample *s) +{ + s->nmi_count = osn_var->nmi.count; + s->irq_count = osn_var->irq.count; + s->softirq_count = osn_var->softirq.count; + s->thread_count = osn_var->thread.count; +} + +/* + * diff_osn_sample_stats - Compute the osnoise_sample statistics + * + * After a sample period, compute the difference on the osnoise_sample + * statistics. The struct osnoise_sample *s contains the statistics saved via + * save_osn_sample_stats() before the osnoise sampling. + */ +static void +diff_osn_sample_stats(struct osnoise_variables *osn_var, struct osnoise_sample *s) +{ + s->nmi_count = osn_var->nmi.count - s->nmi_count; + s->irq_count = osn_var->irq.count - s->irq_count; + s->softirq_count = osn_var->softirq.count - s->softirq_count; + s->thread_count = osn_var->thread.count - s->thread_count; +} + +/* + * osnoise_stop_tracing - Stop tracing and the tracer. + */ +static void osnoise_stop_tracing(void) +{ + struct trace_array *tr = osnoise_trace; + tracer_tracing_off(tr); +} + +/* + * run_osnoise - Sample the time and look for osnoise + * + * Used to capture the time, looking for potential osnoise latency repeatedly. + * Different from hwlat_detector, it is called with preemption and interrupts + * enabled. This allows irqs, softirqs and threads to run, interfering on the + * osnoise sampling thread, as they would do with a regular thread. + */ +static int run_osnoise(void) +{ + struct osnoise_variables *osn_var = this_cpu_osn_var(); + struct trace_array *tr = osnoise_trace; + u64 start, sample, last_sample; + u64 last_int_count, int_count; + s64 noise = 0, max_noise = 0; + s64 total, last_total = 0; + struct osnoise_sample s; + unsigned int threshold; + u64 runtime, stop_in; + u64 sum_noise = 0; + int hw_count = 0; + int ret = -1; + + /* + * Considers the current thread as the workload. + */ + osn_var->pid = current->pid; + + /* + * Save the current stats for the diff + */ + save_osn_sample_stats(osn_var, &s); + + /* + * if threshold is 0, use the default value of 5 us. + */ + threshold = tracing_thresh ? : 5000; + + /* + * Make sure NMIs see sampling first + */ + osn_var->sampling = true; + barrier(); + + /* + * Transform the *_us config to nanoseconds to avoid the + * division on the main loop. + */ + runtime = osnoise_data.sample_runtime * NSEC_PER_USEC; + stop_in = osnoise_data.stop_tracing * NSEC_PER_USEC; + + /* + * Start timestemp + */ + start = time_get(); + + /* + * "previous" loop. + */ + last_int_count = set_int_safe_time(osn_var, &last_sample); + + do { + /* + * Get sample! + */ + int_count = set_int_safe_time(osn_var, &sample); + + noise = time_sub(sample, last_sample); + + /* + * This shouldn't happen. + */ + if (noise < 0) { + osnoise_taint("negative noise!"); + goto out; + } + + /* + * Sample runtime. + */ + total = time_sub(sample, start); + + /* + * Check for possible overflows. + */ + if (total < last_total) { + osnoise_taint("total overflow!"); + break; + } + + last_total = total; + + if (noise >= threshold) { + int interference = int_count - last_int_count; + + if (noise > max_noise) + max_noise = noise; + + if (!interference) + hw_count++; + + sum_noise += noise; + + trace_sample_threshold(last_sample, noise, interference); + + if (osnoise_data.stop_tracing) + if (noise > stop_in) + osnoise_stop_tracing(); + } + + /* + * For the non-preemptive kernel config: let threads runs, if + * they so wish. + */ + cond_resched(); + + last_sample = sample; + last_int_count = int_count; + + } while (total < runtime && !kthread_should_stop()); + + /* + * Finish the above in the view for interrupts. + */ + barrier(); + + osn_var->sampling = false; + + /* + * Make sure sampling data is no longer updated. + */ + barrier(); + + /* + * Save noise info. + */ + s.noise = time_to_us(sum_noise); + s.runtime = time_to_us(total); + s.max_sample = time_to_us(max_noise); + s.hw_count = hw_count; + + /* Save interference stats info */ + diff_osn_sample_stats(osn_var, &s); + + trace_osnoise_sample(&s); + + /* Keep a running maximum ever recorded osnoise "latency" */ + if (max_noise > tr->max_latency) { + tr->max_latency = max_noise; + latency_fsnotify(tr); + } + + if (osnoise_data.stop_tracing_total) + if (s.noise > osnoise_data.stop_tracing_total) + osnoise_stop_tracing(); + + return 0; +out: + return ret; +} |