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Subject[PATCH 5/5][RFC] function-graph: add option to calculate graph time or not
From: Steven Rostedt <srostedt@redhat.com>

graph time is the time that a function is executing another function.
Thus if function A calls B, if graph-time is set, then the time for
A includes B. This is the default behavior. But if graph-time is off,
then the time spent executing B is subtracted from A.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
---
include/linux/ftrace.h | 3 +--
kernel/trace/ftrace.c | 21 ++++++++++++++++++++-
kernel/trace/trace.c | 4 +++-
kernel/trace/trace.h | 1 +
kernel/trace/trace_functions_graph.c | 8 ++++----
5 files changed, 29 insertions(+), 8 deletions(-)
diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index 015a3d2..9e0a8d2 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -365,6 +365,7 @@ struct ftrace_ret_stack {
unsigned long ret;
unsigned long func;
unsigned long long calltime;
+ unsigned long long subtime;
};

/*
@@ -376,8 +377,6 @@ extern void return_to_handler(void);

extern int
ftrace_push_return_trace(unsigned long ret, unsigned long func, int *depth);
-extern void
-ftrace_pop_return_trace(struct ftrace_graph_ret *trace, unsigned long *ret);

/*
* Sometimes we don't want to trace a function with the function
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index ed1fc50..71e5fae 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -604,6 +604,7 @@ static int profile_graph_entry(struct ftrace_graph_ent *trace)
static void profile_graph_return(struct ftrace_graph_ret *trace)
{
struct ftrace_profile_stat *stat;
+ unsigned long long calltime;
struct ftrace_profile *rec;
unsigned long flags;

@@ -612,9 +613,27 @@ static void profile_graph_return(struct ftrace_graph_ret *trace)
if (!stat->hash)
goto out;

+ calltime = trace->rettime - trace->calltime;
+
+ if (!(trace_flags & TRACE_ITER_GRAPH_TIME)) {
+ int index;
+
+ index = trace->depth;
+
+ /* Append this call time to the parent time to subtract */
+ if (index)
+ current->ret_stack[index - 1].subtime += calltime;
+
+ if (current->ret_stack[index].subtime < calltime)
+ calltime -= current->ret_stack[index].subtime;
+ else
+ calltime = 0;
+ }
+
rec = ftrace_find_profiled_func(stat, trace->func);
if (rec)
- rec->time += trace->rettime - trace->calltime;
+ rec->time += calltime;
+
out:
local_irq_restore(flags);
}
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 821bf49..5d1a16c 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -255,7 +255,8 @@ static DECLARE_WAIT_QUEUE_HEAD(trace_wait);

/* trace_flags holds trace_options default values */
unsigned long trace_flags = TRACE_ITER_PRINT_PARENT | TRACE_ITER_PRINTK |
- TRACE_ITER_ANNOTATE | TRACE_ITER_CONTEXT_INFO | TRACE_ITER_SLEEP_TIME;
+ TRACE_ITER_ANNOTATE | TRACE_ITER_CONTEXT_INFO | TRACE_ITER_SLEEP_TIME |
+ TRACE_ITER_GRAPH_TIME;

/**
* trace_wake_up - wake up tasks waiting for trace input
@@ -317,6 +318,7 @@ static const char *trace_options[] = {
"latency-format",
"global-clock",
"sleep-time",
+ "graph-time",
NULL
};

diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index c66ca3b..e3429a8 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -685,6 +685,7 @@ enum trace_iterator_flags {
TRACE_ITER_LATENCY_FMT = 0x40000,
TRACE_ITER_GLOBAL_CLK = 0x80000,
TRACE_ITER_SLEEP_TIME = 0x100000,
+ TRACE_ITER_GRAPH_TIME = 0x200000,
};

/*
diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c
index 85bba0f..10f6ad7 100644
--- a/kernel/trace/trace_functions_graph.c
+++ b/kernel/trace/trace_functions_graph.c
@@ -78,13 +78,14 @@ ftrace_push_return_trace(unsigned long ret, unsigned long func, int *depth)
current->ret_stack[index].ret = ret;
current->ret_stack[index].func = func;
current->ret_stack[index].calltime = calltime;
+ current->ret_stack[index].subtime = 0;
*depth = index;

return 0;
}

/* Retrieve a function return address to the trace stack on thread info.*/
-void
+static void
ftrace_pop_return_trace(struct ftrace_graph_ret *trace, unsigned long *ret)
{
int index;
@@ -104,9 +105,6 @@ ftrace_pop_return_trace(struct ftrace_graph_ret *trace, unsigned long *ret)
trace->calltime = current->ret_stack[index].calltime;
trace->overrun = atomic_read(&current->trace_overrun);
trace->depth = index;
- barrier();
- current->curr_ret_stack--;
-
}

/*
@@ -121,6 +119,8 @@ unsigned long ftrace_return_to_handler(void)
ftrace_pop_return_trace(&trace, &ret);
trace.rettime = trace_clock_local();
ftrace_graph_return(&trace);
+ barrier();
+ current->curr_ret_stack--;

if (unlikely(!ret)) {
ftrace_graph_stop();
--
1.6.2
--


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