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authorNamhyung Kim <namhyung@kernel.org>2016-06-29 13:56:48 +0300
committerSteven Rostedt <rostedt@goodmis.org>2016-07-06 00:28:30 +0300
commita4a551b8f1d4c4ebffd0f49dfef44df3128546f8 (patch)
treef59e73d2d4265f88018dea61756793eb15797604 /include/linux/ftrace.h
parent7ad8fb61c4abf589596f0a4da34d987471481569 (diff)
downloadlinux-a4a551b8f1d4c4ebffd0f49dfef44df3128546f8.tar.xz
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>
Diffstat (limited to 'include/linux/ftrace.h')
-rw-r--r--include/linux/ftrace.h12
1 files changed, 8 insertions, 4 deletions
diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index 66a36a815f0a..7d565afe35d2 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -754,23 +754,27 @@ static inline void ftrace_init(void) { }
/*
* 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 */