Commit a4a551b8 authored by Namhyung Kim's avatar Namhyung Kim Committed by Steven Rostedt
Browse files

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: default avatarNamhyung Kim <namhyung@kernel.org>
Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
parent 7ad8fb61

include/linux/ftrace.h

+8 −4
Original line number Diff line number Diff line
@@ -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 */

kernel/trace/trace.h

+11 −0
Original line number Diff line number Diff line
@@ -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)

kernel/trace/trace_entries.h

+2 −2
Original line number Diff line number Diff line
@@ -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,

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