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| author | Namhyung Kim <namhyung@kernel.org> | 2016-06-29 13:56:48 +0300 |
|---|---|---|
| committer | Steven Rostedt <rostedt@goodmis.org> | 2016-07-06 00:28:30 +0300 |
| commit | a4a551b8f1d4c4ebffd0f49dfef44df3128546f8 (patch) | |
| tree | f59e73d2d4265f88018dea61756793eb15797604 /include/linux/ftrace.h | |
| parent | 7ad8fb61c4abf589596f0a4da34d987471481569 (diff) | |
| download | linux-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.h | 12 |
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 */ |