tracing: Add irq, preempt-count and need resched info to default trace output
People keep asking how to get the preempt count, irq, and need resched info and we keep telling them to enable the latency format. Some developers think that traces without this info is completely useless, and for a lot of tasks it is useless. The first option was to enable the latency trace as the default format, but the header for the latency format is pretty useless for most tracers and it also does the timestamp in straight microseconds from the time the trace started. This is sometimes more difficult to read as the default trace is seconds from the start of boot up. Latency format: # tracer: nop # # nop latency trace v1.1.5 on 3.2.0-rc1-test+ # -------------------------------------------------------------------- # latency: 0 us, #159771/64234230, CPU#1 | (M:preempt VP:0, KP:0, SP:0 HP:0 #P:4) # ----------------- # | task: -0 (uid:0 nice:0 policy:0 rt_prio:0) # ----------------- # # _------=> CPU# # / _-----=> irqs-off # | / _----=> need-resched # || / _---=> hardirq/softirq # ||| / _--=> preempt-depth # |||| / delay # cmd pid ||||| time | caller # \ / ||||| \ | / migratio-6 0...2 41778231us+: rcu_note_context_switch <-__schedule migratio-6 0...2 41778233us : trace_rcu_utilization <-rcu_note_context_switch migratio-6 0...2 41778235us+: rcu_sched_qs <-rcu_note_context_switch migratio-6 0d..2 41778236us+: rcu_preempt_qs <-rcu_note_context_switch migratio-6 0...2 41778238us : trace_rcu_utilization <-rcu_note_context_switch migratio-6 0...2 41778239us+: debug_lockdep_rcu_enabled <-__schedule default format: # tracer: nop # # TASK-PID CPU# TIMESTAMP FUNCTION # | | | | | migration/0-6 [000] 50.025810: rcu_note_context_switch <-__schedule migration/0-6 [000] 50.025812: trace_rcu_utilization <-rcu_note_context_switch migration/0-6 [000] 50.025813: rcu_sched_qs <-rcu_note_context_switch migration/0-6 [000] 50.025815: rcu_preempt_qs <-rcu_note_context_switch migration/0-6 [000] 50.025817: trace_rcu_utilization <-rcu_note_context_switch migration/0-6 [000] 50.025818: debug_lockdep_rcu_enabled <-__schedule migration/0-6 [000] 50.025820: debug_lockdep_rcu_enabled <-__schedule The latency format header has latency information that is pretty meaningless for most tracers. Although some of the header is useful, and we can add that later to the default format as well. What is really useful with the latency format is the irqs-off, need-resched hard/softirq context and the preempt count. This commit adds the option irq-info which is on by default that adds this information: # tracer: nop # # _-----=> irqs-off # / _----=> need-resched # | / _---=> hardirq/softirq # || / _--=> preempt-depth # ||| / delay # TASK-PID CPU# |||| TIMESTAMP FUNCTION # | | | |||| | | <idle>-0 [000] d..2 49.309305: cpuidle_get_driver <-cpuidle_idle_call <idle>-0 [000] d..2 49.309307: mwait_idle <-cpu_idle <idle>-0 [000] d..2 49.309309: need_resched <-mwait_idle <idle>-0 [000] d..2 49.309310: test_ti_thread_flag <-need_resched <idle>-0 [000] d..2 49.309312: trace_power_start.constprop.13 <-mwait_idle <idle>-0 [000] d..2 49.309313: trace_cpu_idle <-mwait_idle <idle>-0 [000] d..2 49.309315: need_resched <-mwait_idle If a user wants the old format, they can disable the 'irq-info' option: # tracer: nop # # TASK-PID CPU# TIMESTAMP FUNCTION # | | | | | <idle>-0 [000] 49.309305: cpuidle_get_driver <-cpuidle_idle_call <idle>-0 [000] 49.309307: mwait_idle <-cpu_idle <idle>-0 [000] 49.309309: need_resched <-mwait_idle <idle>-0 [000] 49.309310: test_ti_thread_flag <-need_resched <idle>-0 [000] 49.309312: trace_power_start.constprop.13 <-mwait_idle <idle>-0 [000] 49.309313: trace_cpu_idle <-mwait_idle <idle>-0 [000] 49.309315: need_resched <-mwait_idle Requested-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
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@ -338,7 +338,8 @@ static DECLARE_WAIT_QUEUE_HEAD(trace_wait);
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/* trace_flags holds trace_options default values */
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unsigned long trace_flags = TRACE_ITER_PRINT_PARENT | TRACE_ITER_PRINTK |
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TRACE_ITER_ANNOTATE | TRACE_ITER_CONTEXT_INFO | TRACE_ITER_SLEEP_TIME |
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TRACE_ITER_GRAPH_TIME | TRACE_ITER_RECORD_CMD | TRACE_ITER_OVERWRITE;
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TRACE_ITER_GRAPH_TIME | TRACE_ITER_RECORD_CMD | TRACE_ITER_OVERWRITE |
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TRACE_ITER_IRQ_INFO;
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static int trace_stop_count;
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static DEFINE_RAW_SPINLOCK(tracing_start_lock);
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@ -426,6 +427,7 @@ static const char *trace_options[] = {
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"record-cmd",
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"overwrite",
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"disable_on_free",
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"irq-info",
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NULL
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};
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@ -1857,10 +1859,20 @@ static void print_lat_help_header(struct seq_file *m)
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static void print_func_help_header(struct seq_file *m)
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{
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seq_puts(m, "# TASK-PID CPU# TIMESTAMP FUNCTION\n");
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seq_puts(m, "# TASK-PID CPU# TIMESTAMP FUNCTION\n");
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seq_puts(m, "# | | | | |\n");
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}
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static void print_func_help_header_irq(struct seq_file *m)
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{
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seq_puts(m, "# _-----=> irqs-off\n");
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seq_puts(m, "# / _----=> need-resched\n");
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seq_puts(m, "# | / _---=> hardirq/softirq\n");
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seq_puts(m, "# || / _--=> preempt-depth\n");
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seq_puts(m, "# ||| / delay\n");
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seq_puts(m, "# TASK-PID CPU# |||| TIMESTAMP FUNCTION\n");
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seq_puts(m, "# | | | |||| | |\n");
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}
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void
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print_trace_header(struct seq_file *m, struct trace_iterator *iter)
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@ -2170,8 +2182,12 @@ void trace_default_header(struct seq_file *m)
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if (!(trace_flags & TRACE_ITER_VERBOSE))
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print_lat_help_header(m);
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} else {
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if (!(trace_flags & TRACE_ITER_VERBOSE))
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print_func_help_header(m);
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if (!(trace_flags & TRACE_ITER_VERBOSE)) {
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if (trace_flags & TRACE_ITER_IRQ_INFO)
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print_func_help_header_irq(m);
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else
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print_func_help_header(m);
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}
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}
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}
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@ -655,6 +655,7 @@ enum trace_iterator_flags {
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TRACE_ITER_RECORD_CMD = 0x100000,
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TRACE_ITER_OVERWRITE = 0x200000,
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TRACE_ITER_STOP_ON_FREE = 0x400000,
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TRACE_ITER_IRQ_INFO = 0x800000,
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};
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/*
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@ -627,11 +627,23 @@ int trace_print_context(struct trace_iterator *iter)
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unsigned long usec_rem = do_div(t, USEC_PER_SEC);
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unsigned long secs = (unsigned long)t;
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char comm[TASK_COMM_LEN];
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int ret;
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trace_find_cmdline(entry->pid, comm);
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return trace_seq_printf(s, "%16s-%-5d [%03d] %5lu.%06lu: ",
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comm, entry->pid, iter->cpu, secs, usec_rem);
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ret = trace_seq_printf(s, "%16s-%-5d [%03d] ",
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comm, entry->pid, iter->cpu);
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if (!ret)
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return 0;
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if (trace_flags & TRACE_ITER_IRQ_INFO) {
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ret = trace_print_lat_fmt(s, entry);
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if (!ret)
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return 0;
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}
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return trace_seq_printf(s, " %5lu.%06lu: ",
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secs, usec_rem);
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}
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int trace_print_lat_context(struct trace_iterator *iter)
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