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Subject[PATCHv2 2/4] tracing: graph output support for irqsoff tracer
Date
hi,

when I was using irqsoff tracer, I thought it could be any use
to see the disabled IRQs flow output same way as function graph output.

The graph output is enabled by setting new 'display-graph' trace option
of irqsoff tracer.

It looks like this:

[root@dell-pe1950-05 tracing]# echo irqsoff-graph > ./trace_options
[root@dell-pe1950-05 tracing]# cat ./trace
# tracer: irqsoff
#
# _-----=> irqs-off
# / _----=> need-resched
# | / _---=> hardirq/softirq
# || / _--=> preempt-depth
# ||| / _-=> lock-depth
# |||| /
# CPU||||| DURATION FUNCTION CALLS
# | ||||| | | | | | |
hald-add-1048 3d...0 0us : _raw_spin_lock_irqsave <-scsi_dispatch_cmd
3) d...0 | ata_scsi_queuecmd() {
3) d...0 0.318 us | _raw_spin_lock();
3) d...0 | ata_scsi_find_dev() {
3) d...0 | __ata_scsi_find_dev() {
3) d...0 0.273 us | ata_find_dev();
3) d...0 0.798 us | }
3) d...0 1.419 us | }
3) d...0 | __ata_scsi_queuecmd() {
3) d...0 | ata_qc_new_init() {
3) d...0 | ata_qc_reinit() {
3) d...0 0.258 us | ata_tf_init();
3) d...0 0.784 us | }
3) d...0 1.441 us | }
3) d...0 0.348 us | atapi_xlat();
3) d...0 | ata_qc_issue() {
...

SNIP

...
3) d...0+ 31.244 us | }
3) d...0+ 32.393 us | }
3) d...0+ 99.146 us | }
3) d...0! 100.455 us | }
3) d...0! 103.669 us | }
3) d...0 0.267 us | _raw_spin_lock();
3) d...0! 107.264 us | }
3) d...0 | spin_unlock_irqrestore() {
3) d...0 | _raw_spin_unlock_irqrestore() {
hald-add-1048 3d...0 109us : _raw_spin_unlock_irqrestore <-return_to_handler
hald-add-1048 3d...0 109us : trace_hardirqs_on <-return_to_handler
hald-add-1048 3d...0 109us : <stack trace>
=> trace_hardirqs_on
=> _raw_spin_unlock_irqrestore
=> return_to_handler
=> scsi_dispatch_cmd
=> return_to_handler
=> __generic_unplug_device
=> scsi_request_fn
=> return_to_handler
[root@dell-pe1950-05 tracing]#

wbr,
jirka


Signed-off-by: Jiri Olsa <jolsa@redhat.com>
---
kernel/trace/trace.h | 8 ++
kernel/trace/trace_functions_graph.c | 25 ++----
kernel/trace/trace_irqsoff.c | 162 ++++++++++++++++++++++++++++++++--
3 files changed, 172 insertions(+), 23 deletions(-)

diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 9992c29..735ec7e 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -492,6 +492,14 @@ extern int trace_clock_id;
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
extern enum print_line_t
trace_print_graph_duration(unsigned long long duration, struct trace_seq *s);
+void graph_trace_open(struct trace_iterator *iter);
+void graph_trace_close(struct trace_iterator *iter);
+int __trace_graph_entry(struct trace_array *tr, struct ftrace_graph_ent *trace,
+ unsigned long flags, int pc);
+void __trace_graph_return(struct trace_array *tr,
+ struct ftrace_graph_ret *trace,
+ unsigned long flags, int pc);
+

#ifdef CONFIG_DYNAMIC_FTRACE
/* TODO: make this variable */
diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c
index b0e6384..78e09f1 100644
--- a/kernel/trace/trace_functions_graph.c
+++ b/kernel/trace/trace_functions_graph.c
@@ -178,7 +178,7 @@ unsigned long ftrace_return_to_handler(unsigned long frame_pointer)
return ret;
}

-static int __trace_graph_entry(struct trace_array *tr,
+int __trace_graph_entry(struct trace_array *tr,
struct ftrace_graph_ent *trace,
unsigned long flags,
int pc)
@@ -237,7 +237,7 @@ int trace_graph_entry(struct ftrace_graph_ent *trace)
return ret;
}

-static void __trace_graph_return(struct trace_array *tr,
+void __trace_graph_return(struct trace_array *tr,
struct ftrace_graph_ret *trace,
unsigned long flags,
int pc)
@@ -944,9 +944,7 @@ static enum print_line_t
print_graph_comment(struct trace_seq *s, struct trace_entry *ent,
struct trace_iterator *iter)
{
- unsigned long sym_flags = (trace_flags & TRACE_ITER_SYM_MASK);
struct fgraph_data *data = iter->private;
- struct trace_event *event;
int depth = 0;
int ret;
int i;
@@ -993,14 +991,6 @@ print_graph_comment(struct trace_seq *s, struct trace_entry *ent,
if (ret != TRACE_TYPE_HANDLED)
return ret;
break;
- default:
- event = ftrace_find_event(ent->type);
- if (!event)
- return TRACE_TYPE_UNHANDLED;
-
- ret = event->trace(iter, sym_flags);
- if (ret != TRACE_TYPE_HANDLED)
- return ret;
}

/* Strip ending newline */
@@ -1066,8 +1056,11 @@ print_graph_function(struct trace_iterator *iter)
trace_assign_type(field, entry);
return print_graph_return(&field->ret, s, entry, iter);
}
- default:
+ case TRACE_BPRINT:
+ case TRACE_PRINT:
return print_graph_comment(s, entry, iter);
+ default:
+ return TRACE_TYPE_UNHANDLED;
}

return TRACE_TYPE_HANDLED;
@@ -1101,7 +1094,7 @@ static void print_lat_header(struct seq_file *s)
seq_printf(s, "#%.*s|||| / \n", size, spaces);
}

-static void print_graph_headers(struct seq_file *s)
+void print_graph_headers(struct seq_file *s)
{
int lat = trace_flags & TRACE_ITER_LATENCY_FMT;

@@ -1137,7 +1130,7 @@ static void print_graph_headers(struct seq_file *s)
seq_printf(s, " | | | |\n");
}

-static void graph_trace_open(struct trace_iterator *iter)
+void graph_trace_open(struct trace_iterator *iter)
{
/* pid and depth on the last trace processed */
struct fgraph_data *data;
@@ -1172,7 +1165,7 @@ static void graph_trace_open(struct trace_iterator *iter)
pr_warning("function graph tracer: not enough memory\n");
}

-static void graph_trace_close(struct trace_iterator *iter)
+void graph_trace_close(struct trace_iterator *iter)
{
struct fgraph_data *data = iter->private;

diff --git a/kernel/trace/trace_irqsoff.c b/kernel/trace/trace_irqsoff.c
index 2974bc7..d0c6d6c 100644
--- a/kernel/trace/trace_irqsoff.c
+++ b/kernel/trace/trace_irqsoff.c
@@ -34,6 +34,9 @@ static int trace_type __read_mostly;

static int save_lat_flag;

+static void stop_irqsoff_tracer(struct trace_array *tr, int graph);
+static int start_irqsoff_tracer(struct trace_array *tr, int graph);
+
#ifdef CONFIG_PREEMPT_TRACER
static inline int
preempt_trace(void)
@@ -55,6 +58,23 @@ irq_trace(void)
# define irq_trace() (0)
#endif

+#define TRACE_DISPLAY_GRAPH 1
+
+static struct tracer_opt trace_opts[] = {
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+ /* display latency trace as call graph */
+ { TRACER_OPT(display-graph, TRACE_DISPLAY_GRAPH) },
+#endif
+ { } /* Empty entry */
+};
+
+static struct tracer_flags tracer_flags = {
+ .val = 0,
+ .opts = trace_opts,
+};
+
+#define is_graph() (tracer_flags.val & TRACE_DISPLAY_GRAPH)
+
/*
* Sequence count - we record it when starting a measurement and
* skip the latency if the sequence has changed - some other section
@@ -108,6 +128,109 @@ static struct ftrace_ops trace_ops __read_mostly =
};
#endif /* CONFIG_FUNCTION_TRACER */

+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+static int irqsoff_set_flag(u32 old_flags, u32 bit, int set)
+{
+ int cpu;
+
+ if (!(bit & TRACE_DISPLAY_GRAPH))
+ return -EINVAL;
+
+ if (!(is_graph() ^ set))
+ return 0;
+
+ stop_irqsoff_tracer(irqsoff_trace, !set);
+
+ for_each_possible_cpu(cpu)
+ per_cpu(tracing_cpu, cpu) = 0;
+
+ tracing_max_latency = 0;
+ tracing_reset_online_cpus(irqsoff_trace);
+
+ return start_irqsoff_tracer(irqsoff_trace, set);
+}
+
+static int irqsoff_graph_entry(struct ftrace_graph_ent *trace)
+{
+ struct trace_array *tr = irqsoff_trace;
+ struct trace_array_cpu *data;
+ unsigned long flags;
+ long disabled;
+ int ret;
+ int cpu;
+ int pc;
+
+ cpu = raw_smp_processor_id();
+ if (likely(!per_cpu(tracing_cpu, cpu)))
+ return 0;
+
+ local_save_flags(flags);
+ /* slight chance to get a false positive on tracing_cpu */
+ if (!irqs_disabled_flags(flags))
+ return 0;
+
+ data = tr->data[cpu];
+ disabled = atomic_inc_return(&data->disabled);
+
+ if (likely(disabled == 1)) {
+ pc = preempt_count();
+ ret = __trace_graph_entry(tr, trace, flags, pc);
+ } else
+ ret = 0;
+
+ atomic_dec(&data->disabled);
+ return ret;
+}
+
+static void irqsoff_graph_return(struct ftrace_graph_ret *trace)
+{
+ struct trace_array *tr = irqsoff_trace;
+ struct trace_array_cpu *data;
+ unsigned long flags;
+ long disabled;
+ int cpu;
+ int pc;
+
+ cpu = raw_smp_processor_id();
+ if (likely(!per_cpu(tracing_cpu, cpu)))
+ return;
+
+ local_save_flags(flags);
+ /* slight chance to get a false positive on tracing_cpu */
+ if (!irqs_disabled_flags(flags))
+ return;
+
+ data = tr->data[cpu];
+ disabled = atomic_inc_return(&data->disabled);
+
+ if (likely(disabled == 1)) {
+ pc = preempt_count();
+ __trace_graph_return(tr, trace, flags, pc);
+ }
+
+ atomic_dec(&data->disabled);
+}
+
+static void irqsoff_trace_open(struct trace_iterator *iter)
+{
+ if (is_graph())
+ graph_trace_open(iter);
+
+}
+
+static void irqsoff_trace_close(struct trace_iterator *iter)
+{
+ if (iter->private)
+ graph_trace_close(iter);
+}
+
+#else
+static int irqsoff_set_flag(u32 old_flags, u32 bit, int set)
+{
+ return -EINVAL;
+}
+#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
+
/*
* Should this new latency be reported/recorded?
*/
@@ -347,19 +470,36 @@ void trace_preempt_off(unsigned long a0, unsigned long a1)
}
#endif /* CONFIG_PREEMPT_TRACER */

-static void start_irqsoff_tracer(struct trace_array *tr)
+static int start_irqsoff_tracer(struct trace_array *tr, int graph)
{
- register_ftrace_function(&trace_ops);
- if (tracing_is_enabled())
+ int ret = 0;
+
+ if (!graph)
+ ret = register_ftrace_function(&trace_ops);
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+ else
+ ret = register_ftrace_graph(&irqsoff_graph_return,
+ &irqsoff_graph_entry);
+#endif
+
+ if (!ret && tracing_is_enabled())
tracer_enabled = 1;
else
tracer_enabled = 0;
+
+ return ret;
}

-static void stop_irqsoff_tracer(struct trace_array *tr)
+static void stop_irqsoff_tracer(struct trace_array *tr, int graph)
{
tracer_enabled = 0;
- unregister_ftrace_function(&trace_ops);
+
+ if (!graph)
+ unregister_ftrace_function(&trace_ops);
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+ else
+ unregister_ftrace_graph();
+#endif
}

static void __irqsoff_tracer_init(struct trace_array *tr)
@@ -372,12 +512,14 @@ static void __irqsoff_tracer_init(struct trace_array *tr)
/* make sure that the tracer is visible */
smp_wmb();
tracing_reset_online_cpus(tr);
- start_irqsoff_tracer(tr);
+
+ if (start_irqsoff_tracer(tr, is_graph()))
+ printk(KERN_ERR "failed to start irqsoff tracer\n");
}

static void irqsoff_tracer_reset(struct trace_array *tr)
{
- stop_irqsoff_tracer(tr);
+ stop_irqsoff_tracer(tr, is_graph());

if (!save_lat_flag)
trace_flags &= ~TRACE_ITER_LATENCY_FMT;
@@ -409,9 +551,15 @@ static struct tracer irqsoff_tracer __read_mostly =
.start = irqsoff_tracer_start,
.stop = irqsoff_tracer_stop,
.print_max = 1,
+ .flags = &tracer_flags,
+ .set_flag = irqsoff_set_flag,
#ifdef CONFIG_FTRACE_SELFTEST
.selftest = trace_selftest_startup_irqsoff,
#endif
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+ .open = irqsoff_trace_open,
+ .close = irqsoff_trace_close,
+#endif
};
# define register_irqsoff(trace) register_tracer(&trace)
#else
--
1.6.6


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