ftrace: Reduce size of function graph entries
Currently ftrace_graph_ent{,_entry} and ftrace_graph_ret{,_entry} struct
can have padding bytes at the end due to alignment in 64-bit data type.
As these data are recorded so frequently, those paddings waste
non-negligible space. As the ring buffer maintains alignment properly
for each architecture, just to remove the extra padding using 'packed'
attribute.
ftrace_graph_ent_entry: 24 -> 20
ftrace_graph_ret_entry: 48 -> 44
Also I moved the 'overrun' field in struct ftrace_graph_ret to minimize
the padding in the middle.
Tested on x86_64 only.
Link: http://lkml.kernel.org/r/1467197808-13578-1-git-send-email-namhyung@kernel.org
Cc: Ingo Molnar <mingo@kernel.org>
Cc: linux-arch@vger.kernel.org
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index 66a36a8..7d565af 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -754,23 +754,27 @@
/*
* Structure that defines an entry function trace.
+ * It's already packed but the attribute "packed" is needed
+ * to remove extra padding at the end.
*/
struct ftrace_graph_ent {
unsigned long func; /* Current function */
int depth;
-};
+} __packed;
/*
* Structure that defines a return function trace.
+ * It's already packed but the attribute "packed" is needed
+ * to remove extra padding at the end.
*/
struct ftrace_graph_ret {
unsigned long func; /* Current function */
- unsigned long long calltime;
- unsigned long long rettime;
/* Number of functions that overran the depth limit for current task */
unsigned long overrun;
+ unsigned long long calltime;
+ unsigned long long rettime;
int depth;
-};
+} __packed;
/* Type of the callback handlers for tracing function graph*/
typedef void (*trace_func_graph_ret_t)(struct ftrace_graph_ret *); /* return */
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index c1de3f4..f783df4 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -80,6 +80,12 @@
FTRACE_ENTRY(name, struct_name, id, PARAMS(tstruct), PARAMS(print), \
filter)
+#undef FTRACE_ENTRY_PACKED
+#define FTRACE_ENTRY_PACKED(name, struct_name, id, tstruct, print, \
+ filter) \
+ FTRACE_ENTRY(name, struct_name, id, PARAMS(tstruct), PARAMS(print), \
+ filter) __packed
+
#include "trace_entries.h"
/*
@@ -1625,6 +1631,11 @@
#define FTRACE_ENTRY_DUP(call, struct_name, id, tstruct, print, filter) \
FTRACE_ENTRY(call, struct_name, id, PARAMS(tstruct), PARAMS(print), \
filter)
+#undef FTRACE_ENTRY_PACKED
+#define FTRACE_ENTRY_PACKED(call, struct_name, id, tstruct, print, filter) \
+ FTRACE_ENTRY(call, struct_name, id, PARAMS(tstruct), PARAMS(print), \
+ filter)
+
#include "trace_entries.h"
#if defined(CONFIG_PERF_EVENTS) && defined(CONFIG_FUNCTION_TRACER)
diff --git a/kernel/trace/trace_entries.h b/kernel/trace/trace_entries.h
index ee7b94a..5c30efc 100644
--- a/kernel/trace/trace_entries.h
+++ b/kernel/trace/trace_entries.h
@@ -72,7 +72,7 @@
);
/* Function call entry */
-FTRACE_ENTRY(funcgraph_entry, ftrace_graph_ent_entry,
+FTRACE_ENTRY_PACKED(funcgraph_entry, ftrace_graph_ent_entry,
TRACE_GRAPH_ENT,
@@ -88,7 +88,7 @@
);
/* Function return entry */
-FTRACE_ENTRY(funcgraph_exit, ftrace_graph_ret_entry,
+FTRACE_ENTRY_PACKED(funcgraph_exit, ftrace_graph_ret_entry,
TRACE_GRAPH_RET,