tracing/function-graph-tracer: use the more lightweight local clock

Impact: decrease hangs risks with the graph tracer on slow systems

Since the function graph tracer can spend too much time on timer
interrupts, it's better now to use the more lightweight local
clock. Anyway, the function graph traces are more reliable on a
per cpu trace.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Peter Zijlstra <peterz@infradead.org>
LKML-Reference: <49af243d.06e9300a.53ad.ffff840c@mx.google.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
index 3925ec0..a85da17 100644 (file)
--- a/arch/x86/kernel/ftrace.c
+++ b/arch/x86/kernel/ftrace.c
@@ -436,7 +436,7 @@ void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr)
                return;
        }
 
-       calltime = cpu_clock(raw_smp_processor_id());
+       calltime = trace_clock_local();
 
        if (ftrace_push_return_trace(old, calltime,
                                self_addr, &trace.depth) == -EBUSY) {

diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index 1f69ac7..6ea62ac 100644 (file)
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -1,15 +1,16 @@
 #ifndef _LINUX_FTRACE_H
 #define _LINUX_FTRACE_H
 
-#include <linux/linkage.h>
-#include <linux/fs.h>
-#include <linux/ktime.h>
-#include <linux/init.h>
-#include <linux/types.h>
-#include <linux/module.h>
+#include <linux/trace_clock.h>
 #include <linux/kallsyms.h>
+#include <linux/linkage.h>
 #include <linux/bitops.h>
+#include <linux/module.h>
+#include <linux/ktime.h>
 #include <linux/sched.h>
+#include <linux/types.h>
+#include <linux/init.h>
+#include <linux/fs.h>
 
 #include <asm/ftrace.h>
 

diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c
index c009553..e527f2f 100644 (file)
--- a/kernel/trace/trace_functions_graph.c
+++ b/kernel/trace/trace_functions_graph.c
@@ -112,7 +112,7 @@ unsigned long ftrace_return_to_handler(void)
        unsigned long ret;
 
        ftrace_pop_return_trace(&trace, &ret);
-       trace.rettime = cpu_clock(raw_smp_processor_id());
+       trace.rettime = trace_clock_local();
        ftrace_graph_return(&trace);
 
        if (unlikely(!ret)) {