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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>
This commit is contained in:
Namhyung Kim 2016-06-29 19:56:48 +09:00 committed by Steven Rostedt
parent 7ad8fb61c4
commit a4a551b8f1
3 changed files with 21 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

12
include/linux/ftrace.h
View File

@ -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 */

11
kernel/trace/trace.h
View File

@ -80,6 +80,12 @@ enum trace_type {
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 @@ int set_tracer_flag(struct trace_array *tr, unsigned int mask, int enabled);
#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)

4
kernel/trace/trace_entries.h
View File

@ -72,7 +72,7 @@ FTRACE_ENTRY_REG(function, ftrace_entry,
);
/* 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 @@ FTRACE_ENTRY(funcgraph_entry, ftrace_graph_ent_entry,
);
/* Function return entry */
FTRACE_ENTRY(funcgraph_exit, ftrace_graph_ret_entry,
FTRACE_ENTRY_PACKED(funcgraph_exit, ftrace_graph_ret_entry,
TRACE_GRAPH_RET,