perf report: Show branch type

It is often useful to know the branch types while analyzing branch data. For example, a call is very different from a conditional branch.

Currently we have to look it up in binary while the binary may later not be available and even the binary is available but user has to take some time. It is very useful for user to check it directly in perf report.

Perf already has support for disassembling the branch instruction to get the branch type. The branch type is defined in lbr.c.

To keep consistent on kernel and userspace and make the classification more common, the patch adds the common branch type classification in perf_event.h.

Since the disassembling of branch instruction needs some overhead, a new PERF_SAMPLE_BRANCH_TYPE_SAVE is introduced to indicate if it needs to disassemble the branch instruction and record the branch type.

Signed-off-by Jin Yao <[email protected]>

---
 include/uapi/linux/perf_event.h       | 24 +++++++++++++++++++++++-
 tools/include/uapi/linux/perf_event.h | 24 +++++++++++++++++++++++-
 2 files changed, 46 insertions(+), 2 deletions(-)

include/uapi/linux/perf_event.h +8 -0

index d09a9cd..4d731fd 100644
@@ -174,6 +174,8 @@ enum perf_branch_sample_type_shift {
 	PERF_SAMPLE_BRANCH_NO_FLAGS_SHIFT	= 14, /* no flags */
 	PERF_SAMPLE_BRANCH_NO_CYCLES_SHIFT	= 15, /* no cycles */
 
+	PERF_SAMPLE_BRANCH_TYPE_SAVE_SHIFT	= 16, /* save branch type */
+
 	PERF_SAMPLE_BRANCH_MAX_SHIFT		/* non-ABI */
 };
 

@@ -198,9 +200,27 @@ enum perf_branch_sample_type {
 	PERF_SAMPLE_BRANCH_NO_FLAGS	= 1U << PERF_SAMPLE_BRANCH_NO_FLAGS_SHIFT,
 	PERF_SAMPLE_BRANCH_NO_CYCLES	= 1U << PERF_SAMPLE_BRANCH_NO_CYCLES_SHIFT,
 
+	PERF_SAMPLE_BRANCH_TYPE_SAVE	=
+		1U << PERF_SAMPLE_BRANCH_TYPE_SAVE_SHIFT,
+
 	PERF_SAMPLE_BRANCH_MAX		= 1U << PERF_SAMPLE_BRANCH_MAX_SHIFT,
 };
 
+/*
+ * Common flow change classification
+ */

include/uapi/linux/perf_event.h +5 -1

+};
+
 #define PERF_SAMPLE_BRANCH_PLM_ALL \
 	(PERF_SAMPLE_BRANCH_USER|\
 	 PERF_SAMPLE_BRANCH_KERNEL|\

@@ -999,6 +1019,7 @@ union perf_mem_data_src {
  *     in_tx: running in a hardware transaction
  *     abort: aborting a hardware transaction
  *    cycles: cycles from last branch (or 0 if not supported)
+ *      type: branch type
  */
 struct perf_branch_entry {
 	__u64	from;

@@ -1008,7 +1029,8 @@ struct perf_branch_entry {
 		in_tx:1,    /* in transaction */
 		abort:1,    /* transaction abort */
 		cycles:16,  /* cycle count to last branch */
-		reserved:44;
+		type:9,     /* branch type */
+		reserved:35;
 };
 
 #endif /* _UAPI_LINUX_PERF_EVENT_H */

tools/include/uapi/linux/perf_event.h +23 -1

index d09a9cd..4d731fd 100644
@@ -174,6 +174,8 @@ enum perf_branch_sample_type_shift {
 	PERF_SAMPLE_BRANCH_NO_FLAGS_SHIFT	= 14, /* no flags */
 	PERF_SAMPLE_BRANCH_NO_CYCLES_SHIFT	= 15, /* no cycles */
 
+	PERF_SAMPLE_BRANCH_TYPE_SAVE_SHIFT	= 16, /* save branch type */
+
 	PERF_SAMPLE_BRANCH_MAX_SHIFT		/* non-ABI */
 };
 

@@ -198,9 +200,27 @@ enum perf_branch_sample_type {
 	PERF_SAMPLE_BRANCH_NO_FLAGS	= 1U << PERF_SAMPLE_BRANCH_NO_FLAGS_SHIFT,
 	PERF_SAMPLE_BRANCH_NO_CYCLES	= 1U << PERF_SAMPLE_BRANCH_NO_CYCLES_SHIFT,
 
+	PERF_SAMPLE_BRANCH_TYPE_SAVE	=
+		1U << PERF_SAMPLE_BRANCH_TYPE_SAVE_SHIFT,
+
 	PERF_SAMPLE_BRANCH_MAX		= 1U << PERF_SAMPLE_BRANCH_MAX_SHIFT,
 };
 
+/*
+ * Common flow change classification
+ */
+enum {
+	PERF_BR_NONE		= 0,		/* unknown */
+	PERF_BR_JCC_FWD		= 1 << 1,	/* conditional forward jump */
+	PERF_BR_JCC_BWD		= 1 << 2,	/* conditional backward jump */
+	PERF_BR_JMP		= 1 << 3,	/* jump */
+	PERF_BR_IND_JMP		= 1 << 4,	/* indirect jump */
+	PERF_BR_CALL		= 1 << 5,	/* call */
+	PERF_BR_IND_CALL	= 1 << 6,	/* indirect call */
+	PERF_BR_RET		= 1 << 7,	/* return */
+	PERF_BR_FAR_BRANCH	= 1 << 8,	/* SYSCALL,SYSRET,IRQ,... */
+};
+
 #define PERF_SAMPLE_BRANCH_PLM_ALL \
 	(PERF_SAMPLE_BRANCH_USER|\
 	 PERF_SAMPLE_BRANCH_KERNEL|\

@@ -999,6 +1019,7 @@ union perf_mem_data_src {
  *     in_tx: running in a hardware transaction
  *     abort: aborting a hardware transaction
  *    cycles: cycles from last branch (or 0 if not supported)
+ *      type: branch type
  */
 struct perf_branch_entry {
 	__u64	from;

@@ -1008,7 +1029,8 @@ struct perf_branch_entry {
 		in_tx:1,    /* in transaction */
 		abort:1,    /* transaction abort */
 		cycles:16,  /* cycle count to last branch */
-		reserved:44;
+		type:9,     /* branch type */
+		reserved:35;
 };
 
 #endif /* _UAPI_LINUX_PERF_EVENT_H */

Signature · 1 line

2.7.4

Adding the perf kernel maintainers to the CC list.

Em Fri, Mar 31, 2017 at 11:18:38PM +0800, Jin Yao escreveu:

Quoted 52 lines

It is often useful to know the branch types while analyzing branch data. For example, a call is very different from a conditional branch.

Currently we have to look it up in binary while the binary may later not be available and even the binary is available but user has to take some time. It is very useful for user to check it directly in perf report.

Perf already has support for disassembling the branch instruction to get the branch type. The branch type is defined in lbr.c.

To keep consistent on kernel and userspace and make the classification more common, the patch adds the common branch type classification in perf_event.h.

Since the disassembling of branch instruction needs some overhead, a new PERF_SAMPLE_BRANCH_TYPE_SAVE is introduced to indicate if it needs to disassemble the branch instruction and record the branch type.

Signed-off-by Jin Yao <[email protected]>

---
  include/uapi/linux/perf_event.h       | 24 +++++++++++++++++++++++-
  tools/include/uapi/linux/perf_event.h | 24 +++++++++++++++++++++++-
  2 files changed, 46 insertions(+), 2 deletions(-)

include/uapi/linux/perf_event.h +8 -0

index d09a9cd..4d731fd 100644
@@ -174,6 +174,8 @@ enum perf_branch_sample_type_shift {
  	PERF_SAMPLE_BRANCH_NO_FLAGS_SHIFT	= 14, /* no flags */
  	PERF_SAMPLE_BRANCH_NO_CYCLES_SHIFT	= 15, /* no cycles */
 
+	PERF_SAMPLE_BRANCH_TYPE_SAVE_SHIFT	= 16, /* save branch type */
+
  	PERF_SAMPLE_BRANCH_MAX_SHIFT		/* non-ABI */
  };
 

@@ -198,9 +200,27 @@ enum perf_branch_sample_type {
  	PERF_SAMPLE_BRANCH_NO_FLAGS	= 1U << PERF_SAMPLE_BRANCH_NO_FLAGS_SHIFT,
  	PERF_SAMPLE_BRANCH_NO_CYCLES	= 1U << PERF_SAMPLE_BRANCH_NO_CYCLES_SHIFT,
 
+	PERF_SAMPLE_BRANCH_TYPE_SAVE	=
+		1U << PERF_SAMPLE_BRANCH_TYPE_SAVE_SHIFT,
+
  	PERF_SAMPLE_BRANCH_MAX		= 1U << PERF_SAMPLE_BRANCH_MAX_SHIFT,
  };
 
+/*
+ * Common flow change classification
+ */

include/uapi/linux/perf_event.h enum perf_branch_sample_type { · line 221

Quoted 10 lines

include/uapi/linux/perf_event.h +10 -0

+enum {
+	PERF_BR_NONE		= 0,		/* unknown */
+	PERF_BR_JCC_FWD		= 1 << 1,	/* conditional forward jump */
+	PERF_BR_JCC_BWD		= 1 << 2,	/* conditional backward jump */
+	PERF_BR_JMP		= 1 << 3,	/* jump */
+	PERF_BR_IND_JMP		= 1 << 4,	/* indirect jump */
+	PERF_BR_CALL		= 1 << 5,	/* call */
+	PERF_BR_IND_CALL	= 1 << 6,	/* indirect call */
+	PERF_BR_RET		= 1 << 7,	/* return */
+	PERF_BR_FAR_BRANCH	= 1 << 8,	/* SYSCALL,SYSRET,IRQ,... */

Humm, wouldn't be better to have those in separate buckets? I.e.

PERF_BR_SYSCALL
PERF_BR_SYSRET,
PERF_BR_IRQ

etc?

And why a bitmask? /me reads a bit more... couldn't find a reason for this:

+ type:9, /* branch type */

Do you have a reason to use 9 bits? Why not just:

enum {
	PERF_BR_NONE		= 0,	/* unknown */
	PERF_BR_JCC_FWD		= 1,	/* conditional forward jump */
	PERF_BR_JCC_BWD		= 2,	/* conditional backward jump */
	PERF_BR_JMP		= 3,	/* jump */
	PERF_BR_IND_JMP		= 4,	/* indirect jump */
	PERF_BR_CALL		= 5,	/* call */
	PERF_BR_IND_CALL	= 6,	/* indirect call */
	PERF_BR_RET		= 7,	/* return */
	PERF_BR_FAR_BRANCH	= 8,	/* SYSCALL,SYSRET,IRQ,... */

And then use, say, 4 or 5 bits for that type field?

I must be missing something trivial ;-\

- Arnaldo

Quoted 85 lines

include/uapi/linux/perf_event.h +5 -1

+};
+
  #define PERF_SAMPLE_BRANCH_PLM_ALL \
  	(PERF_SAMPLE_BRANCH_USER|\
  	 PERF_SAMPLE_BRANCH_KERNEL|\

@@ -999,6 +1019,7 @@ union perf_mem_data_src {
   *     in_tx: running in a hardware transaction
   *     abort: aborting a hardware transaction
   *    cycles: cycles from last branch (or 0 if not supported)
+ *      type: branch type
   */
  struct perf_branch_entry {
  	__u64	from;

@@ -1008,7 +1029,8 @@ struct perf_branch_entry {
  		in_tx:1,    /* in transaction */
  		abort:1,    /* transaction abort */
  		cycles:16,  /* cycle count to last branch */
-		reserved:44;
+		type:9,     /* branch type */
+		reserved:35;
  };
 
  #endif /* _UAPI_LINUX_PERF_EVENT_H */

tools/include/uapi/linux/perf_event.h +23 -1

index d09a9cd..4d731fd 100644
@@ -174,6 +174,8 @@ enum perf_branch_sample_type_shift {
  	PERF_SAMPLE_BRANCH_NO_FLAGS_SHIFT	= 14, /* no flags */
  	PERF_SAMPLE_BRANCH_NO_CYCLES_SHIFT	= 15, /* no cycles */
 
+	PERF_SAMPLE_BRANCH_TYPE_SAVE_SHIFT	= 16, /* save branch type */
+
  	PERF_SAMPLE_BRANCH_MAX_SHIFT		/* non-ABI */
  };
 

@@ -198,9 +200,27 @@ enum perf_branch_sample_type {
  	PERF_SAMPLE_BRANCH_NO_FLAGS	= 1U << PERF_SAMPLE_BRANCH_NO_FLAGS_SHIFT,
  	PERF_SAMPLE_BRANCH_NO_CYCLES	= 1U << PERF_SAMPLE_BRANCH_NO_CYCLES_SHIFT,
 
+	PERF_SAMPLE_BRANCH_TYPE_SAVE	=
+		1U << PERF_SAMPLE_BRANCH_TYPE_SAVE_SHIFT,
+
  	PERF_SAMPLE_BRANCH_MAX		= 1U << PERF_SAMPLE_BRANCH_MAX_SHIFT,
  };
 
+/*
+ * Common flow change classification
+ */
+enum {
+	PERF_BR_NONE		= 0,		/* unknown */
+	PERF_BR_JCC_FWD		= 1 << 1,	/* conditional forward jump */
+	PERF_BR_JCC_BWD		= 1 << 2,	/* conditional backward jump */
+	PERF_BR_JMP		= 1 << 3,	/* jump */
+	PERF_BR_IND_JMP		= 1 << 4,	/* indirect jump */
+	PERF_BR_CALL		= 1 << 5,	/* call */
+	PERF_BR_IND_CALL	= 1 << 6,	/* indirect call */
+	PERF_BR_RET		= 1 << 7,	/* return */
+	PERF_BR_FAR_BRANCH	= 1 << 8,	/* SYSCALL,SYSRET,IRQ,... */
+};
+
  #define PERF_SAMPLE_BRANCH_PLM_ALL \
  	(PERF_SAMPLE_BRANCH_USER|\
  	 PERF_SAMPLE_BRANCH_KERNEL|\

@@ -999,6 +1019,7 @@ union perf_mem_data_src {
   *     in_tx: running in a hardware transaction
   *     abort: aborting a hardware transaction
   *    cycles: cycles from last branch (or 0 if not supported)
+ *      type: branch type
   */
  struct perf_branch_entry {
  	__u64	from;

@@ -1008,7 +1029,8 @@ struct perf_branch_entry {
  		in_tx:1,    /* in transaction */
  		abort:1,    /* transaction abort */
  		cycles:16,  /* cycle count to last branch */
-		reserved:44;
+		type:9,     /* branch type */
+		reserved:35;
  };
 
  #endif /* _UAPI_LINUX_PERF_EVENT_H */

Signature · 1 line

2.7.4

Quoted 67 lines

Adding the perf kernel maintainers to the CC list.

Em Fri, Mar 31, 2017 at 11:18:38PM +0800, Jin Yao escreveu:

Quoted 48 lines

It is often useful to know the branch types while analyzing branch data. For example, a call is very different from a conditional branch.

Currently we have to look it up in binary while the binary may later not be available and even the binary is available but user has to take some time. It is very useful for user to check it directly in perf report.

Perf already has support for disassembling the branch instruction to get the branch type. The branch type is defined in lbr.c.

To keep consistent on kernel and userspace and make the classification more common, the patch adds the common branch type classification in perf_event.h.

Since the disassembling of branch instruction needs some overhead, a new PERF_SAMPLE_BRANCH_TYPE_SAVE is introduced to indicate if it needs to disassemble the branch instruction and record the branch type.

Signed-off-by Jin Yao <[email protected]>

---
  include/uapi/linux/perf_event.h       | 24 +++++++++++++++++++++++-
  tools/include/uapi/linux/perf_event.h | 24 +++++++++++++++++++++++-
  2 files changed, 46 insertions(+), 2 deletions(-)

include/uapi/linux/perf_event.h +8 -0

index d09a9cd..4d731fd 100644
@@ -174,6 +174,8 @@ enum perf_branch_sample_type_shift {
  	PERF_SAMPLE_BRANCH_NO_FLAGS_SHIFT	= 14, /* no flags */
  	PERF_SAMPLE_BRANCH_NO_CYCLES_SHIFT	= 15, /* no cycles */
+	PERF_SAMPLE_BRANCH_TYPE_SAVE_SHIFT	= 16, /* save branch type */
+
  	PERF_SAMPLE_BRANCH_MAX_SHIFT		/* non-ABI */
  };

@@ -198,9 +200,27 @@ enum perf_branch_sample_type {
  	PERF_SAMPLE_BRANCH_NO_FLAGS	= 1U << PERF_SAMPLE_BRANCH_NO_FLAGS_SHIFT,
  	PERF_SAMPLE_BRANCH_NO_CYCLES	= 1U << PERF_SAMPLE_BRANCH_NO_CYCLES_SHIFT,
+	PERF_SAMPLE_BRANCH_TYPE_SAVE	=
+		1U << PERF_SAMPLE_BRANCH_TYPE_SAVE_SHIFT,
+
  	PERF_SAMPLE_BRANCH_MAX		= 1U << PERF_SAMPLE_BRANCH_MAX_SHIFT,
  };
+/*
+ * Common flow change classification
+ */

include/uapi/linux/perf_event.h enum perf_branch_sample_type { · line 219

Quoted 10 lines

include/uapi/linux/perf_event.h +10 -0

+enum {
+	PERF_BR_NONE		= 0,		/* unknown */
+	PERF_BR_JCC_FWD		= 1 << 1,	/* conditional forward jump */
+	PERF_BR_JCC_BWD		= 1 << 2,	/* conditional backward jump */
+	PERF_BR_JMP		= 1 << 3,	/* jump */
+	PERF_BR_IND_JMP		= 1 << 4,	/* indirect jump */
+	PERF_BR_CALL		= 1 << 5,	/* call */
+	PERF_BR_IND_CALL	= 1 << 6,	/* indirect call */
+	PERF_BR_RET		= 1 << 7,	/* return */
+	PERF_BR_FAR_BRANCH	= 1 << 8,	/* SYSCALL,SYSRET,IRQ,... */

Humm, wouldn't be better to have those in separate buckets? I.e.

PERF_BR_SYSCALL
PERF_BR_SYSRET,
PERF_BR_IRQ

Quoted 1 line

etc?

There are also other types. I.e. abort, ..... I use FAR_BRANCH is because I just want to differentiate between basic branch types and others. (others may be too much and platform specific).

Quoted 18 lines

And why a bitmask? /me reads a bit more... couldn't find a reason for this:

+ type:9, /* branch type */

Do you have a reason to use 9 bits? Why not just:

enum {
	PERF_BR_NONE		= 0,	/* unknown */
	PERF_BR_JCC_FWD		= 1,	/* conditional forward jump */
	PERF_BR_JCC_BWD		= 2,	/* conditional backward jump */
	PERF_BR_JMP		= 3,	/* jump */
	PERF_BR_IND_JMP		= 4,	/* indirect jump */
	PERF_BR_CALL		= 5,	/* call */
	PERF_BR_IND_CALL	= 6,	/* indirect call */
	PERF_BR_RET		= 7,	/* return */
	PERF_BR_FAR_BRANCH	= 8,	/* SYSCALL,SYSRET,IRQ,... */

Quoted 5 lines

And then use, say, 4 or 5 bits for that type field?

I must be missing something trivial ;-\

- Arnaldo

You are right. I made things more complicated. Yes, the definitions should be clear and simple. I will redefine them in v2.

Thanks
Jin Yao

Quoted 79 lines

Quoted 79 lines

include/uapi/linux/perf_event.h +5 -1

+};
+
  #define PERF_SAMPLE_BRANCH_PLM_ALL \
  	(PERF_SAMPLE_BRANCH_USER|\
  	 PERF_SAMPLE_BRANCH_KERNEL|\

@@ -999,6 +1019,7 @@ union perf_mem_data_src {
   *     in_tx: running in a hardware transaction
   *     abort: aborting a hardware transaction
   *    cycles: cycles from last branch (or 0 if not supported)
+ *      type: branch type
   */
  struct perf_branch_entry {
  	__u64	from;

@@ -1008,7 +1029,8 @@ struct perf_branch_entry {
  		in_tx:1,    /* in transaction */
  		abort:1,    /* transaction abort */
  		cycles:16,  /* cycle count to last branch */
-		reserved:44;
+		type:9,     /* branch type */
+		reserved:35;
  };
  #endif /* _UAPI_LINUX_PERF_EVENT_H */

tools/include/uapi/linux/perf_event.h +23 -1

index d09a9cd..4d731fd 100644
@@ -174,6 +174,8 @@ enum perf_branch_sample_type_shift {
  	PERF_SAMPLE_BRANCH_NO_FLAGS_SHIFT	= 14, /* no flags */
  	PERF_SAMPLE_BRANCH_NO_CYCLES_SHIFT	= 15, /* no cycles */
+	PERF_SAMPLE_BRANCH_TYPE_SAVE_SHIFT	= 16, /* save branch type */
+
  	PERF_SAMPLE_BRANCH_MAX_SHIFT		/* non-ABI */
  };

@@ -198,9 +200,27 @@ enum perf_branch_sample_type {
  	PERF_SAMPLE_BRANCH_NO_FLAGS	= 1U << PERF_SAMPLE_BRANCH_NO_FLAGS_SHIFT,
  	PERF_SAMPLE_BRANCH_NO_CYCLES	= 1U << PERF_SAMPLE_BRANCH_NO_CYCLES_SHIFT,
+	PERF_SAMPLE_BRANCH_TYPE_SAVE	=
+		1U << PERF_SAMPLE_BRANCH_TYPE_SAVE_SHIFT,
+
  	PERF_SAMPLE_BRANCH_MAX		= 1U << PERF_SAMPLE_BRANCH_MAX_SHIFT,
  };
+/*
+ * Common flow change classification
+ */
+enum {
+	PERF_BR_NONE		= 0,		/* unknown */
+	PERF_BR_JCC_FWD		= 1 << 1,	/* conditional forward jump */
+	PERF_BR_JCC_BWD		= 1 << 2,	/* conditional backward jump */
+	PERF_BR_JMP		= 1 << 3,	/* jump */
+	PERF_BR_IND_JMP		= 1 << 4,	/* indirect jump */
+	PERF_BR_CALL		= 1 << 5,	/* call */
+	PERF_BR_IND_CALL	= 1 << 6,	/* indirect call */
+	PERF_BR_RET		= 1 << 7,	/* return */
+	PERF_BR_FAR_BRANCH	= 1 << 8,	/* SYSCALL,SYSRET,IRQ,... */
+};
+
  #define PERF_SAMPLE_BRANCH_PLM_ALL \
  	(PERF_SAMPLE_BRANCH_USER|\
  	 PERF_SAMPLE_BRANCH_KERNEL|\

@@ -999,6 +1019,7 @@ union perf_mem_data_src {
   *     in_tx: running in a hardware transaction
   *     abort: aborting a hardware transaction
   *    cycles: cycles from last branch (or 0 if not supported)
+ *      type: branch type
   */
  struct perf_branch_entry {
  	__u64	from;

@@ -1008,7 +1029,8 @@ struct perf_branch_entry {
  		in_tx:1,    /* in transaction */
  		abort:1,    /* transaction abort */
  		cycles:16,  /* cycle count to last branch */
-		reserved:44;
+		type:9,     /* branch type */
+		reserved:35;
  };
  #endif /* _UAPI_LINUX_PERF_EVENT_H */

Signature · 1 line

2.7.4

Em Tue, Apr 04, 2017 at 11:52:53PM +0800, Jin, Yao escreveu:

Quoted 65 lines · Arnaldo Carvalho de Melo

Quoted 63 lines

Adding the perf kernel maintainers to the CC list.

Em Fri, Mar 31, 2017 at 11:18:38PM +0800, Jin Yao escreveu:

Quoted 48 lines

It is often useful to know the branch types while analyzing branch data. For example, a call is very different from a conditional branch.

Currently we have to look it up in binary while the binary may later not be available and even the binary is available but user has to take some time. It is very useful for user to check it directly in perf report.

Perf already has support for disassembling the branch instruction to get the branch type. The branch type is defined in lbr.c.

To keep consistent on kernel and userspace and make the classification more common, the patch adds the common branch type classification in perf_event.h.

Since the disassembling of branch instruction needs some overhead, a new PERF_SAMPLE_BRANCH_TYPE_SAVE is introduced to indicate if it needs to disassemble the branch instruction and record the branch type.

Signed-off-by Jin Yao <[email protected]>

---
   include/uapi/linux/perf_event.h       | 24 +++++++++++++++++++++++-
   tools/include/uapi/linux/perf_event.h | 24 +++++++++++++++++++++++-
   2 files changed, 46 insertions(+), 2 deletions(-)

include/uapi/linux/perf_event.h +8 -0

index d09a9cd..4d731fd 100644
@@ -174,6 +174,8 @@ enum perf_branch_sample_type_shift {
   	PERF_SAMPLE_BRANCH_NO_FLAGS_SHIFT	= 14, /* no flags */
   	PERF_SAMPLE_BRANCH_NO_CYCLES_SHIFT	= 15, /* no cycles */
+	PERF_SAMPLE_BRANCH_TYPE_SAVE_SHIFT	= 16, /* save branch type */
+
   	PERF_SAMPLE_BRANCH_MAX_SHIFT		/* non-ABI */
   };

@@ -198,9 +200,27 @@ enum perf_branch_sample_type {
   	PERF_SAMPLE_BRANCH_NO_FLAGS	= 1U << PERF_SAMPLE_BRANCH_NO_FLAGS_SHIFT,
   	PERF_SAMPLE_BRANCH_NO_CYCLES	= 1U << PERF_SAMPLE_BRANCH_NO_CYCLES_SHIFT,
+	PERF_SAMPLE_BRANCH_TYPE_SAVE	=
+		1U << PERF_SAMPLE_BRANCH_TYPE_SAVE_SHIFT,
+
   	PERF_SAMPLE_BRANCH_MAX		= 1U << PERF_SAMPLE_BRANCH_MAX_SHIFT,
   };
+/*
+ * Common flow change classification
+ */

include/uapi/linux/perf_event.h enum perf_branch_sample_type { · line 219

Quoted 10 lines

include/uapi/linux/perf_event.h +10 -0

+enum {
+	PERF_BR_NONE		= 0,		/* unknown */
+	PERF_BR_JCC_FWD		= 1 << 1,	/* conditional forward jump */
+	PERF_BR_JCC_BWD		= 1 << 2,	/* conditional backward jump */
+	PERF_BR_JMP		= 1 << 3,	/* jump */
+	PERF_BR_IND_JMP		= 1 << 4,	/* indirect jump */
+	PERF_BR_CALL		= 1 << 5,	/* call */
+	PERF_BR_IND_CALL	= 1 << 6,	/* indirect call */
+	PERF_BR_RET		= 1 << 7,	/* return */
+	PERF_BR_FAR_BRANCH	= 1 << 8,	/* SYSCALL,SYSRET,IRQ,... */

Humm, wouldn't be better to have those in separate buckets? I.e.

Quoted 8 lines

Quoted 5 lines

PERF_BR_SYSCALL
PERF_BR_SYSRET,
PERF_BR_IRQ

etc?

There are also other types. I.e. abort, ..... I use FAR_BRANCH is because I just want to differentiate between basic branch types and others. (others may be too much and platform specific).

I understand that this is what you need right now, but "syscall", "sysret", "irq", look generic enough, no?

Really, really arch specific stuff could indeed be lumped together in a FAR_BRANCH, but those used as an example, above (/* SYSCALL,SYSRET,IRQ,... */) seems potentially useful to have untangled?

Quoted 18 lines

Quoted 18 lines

And why a bitmask? /me reads a bit more... couldn't find a reason for this:

+ type:9, /* branch type */

Do you have a reason to use 9 bits? Why not just:

enum {
	PERF_BR_NONE		= 0,	/* unknown */
	PERF_BR_JCC_FWD		= 1,	/* conditional forward jump */
	PERF_BR_JCC_BWD		= 2,	/* conditional backward jump */
	PERF_BR_JMP		= 3,	/* jump */
	PERF_BR_IND_JMP		= 4,	/* indirect jump */
	PERF_BR_CALL		= 5,	/* call */
	PERF_BR_IND_CALL	= 6,	/* indirect call */
	PERF_BR_RET		= 7,	/* return */
	PERF_BR_FAR_BRANCH	= 8,	/* SYSCALL,SYSRET,IRQ,... */

Quoted 7 lines

Quoted 5 lines

And then use, say, 4 or 5 bits for that type field?

I must be missing something trivial ;-\

- Arnaldo

You are right. I made things more complicated. Yes, the definitions should be clear and simple. I will redefine them in v2.

Thanks, I wasn't missing anything, uff :-)

Quoted 81 lines

Thanks
Jin Yao

Quoted 78 lines

Quoted 78 lines

include/uapi/linux/perf_event.h +5 -1

+};
+
   #define PERF_SAMPLE_BRANCH_PLM_ALL \
   	(PERF_SAMPLE_BRANCH_USER|\
   	 PERF_SAMPLE_BRANCH_KERNEL|\

@@ -999,6 +1019,7 @@ union perf_mem_data_src {
    *     in_tx: running in a hardware transaction
    *     abort: aborting a hardware transaction
    *    cycles: cycles from last branch (or 0 if not supported)
+ *      type: branch type
    */
   struct perf_branch_entry {
   	__u64	from;

@@ -1008,7 +1029,8 @@ struct perf_branch_entry {
   		in_tx:1,    /* in transaction */
   		abort:1,    /* transaction abort */
   		cycles:16,  /* cycle count to last branch */
-		reserved:44;
+		type:9,     /* branch type */
+		reserved:35;
   };
   #endif /* _UAPI_LINUX_PERF_EVENT_H */

tools/include/uapi/linux/perf_event.h +23 -1

index d09a9cd..4d731fd 100644
@@ -174,6 +174,8 @@ enum perf_branch_sample_type_shift {
   	PERF_SAMPLE_BRANCH_NO_FLAGS_SHIFT	= 14, /* no flags */
   	PERF_SAMPLE_BRANCH_NO_CYCLES_SHIFT	= 15, /* no cycles */
+	PERF_SAMPLE_BRANCH_TYPE_SAVE_SHIFT	= 16, /* save branch type */
+
   	PERF_SAMPLE_BRANCH_MAX_SHIFT		/* non-ABI */
   };

@@ -198,9 +200,27 @@ enum perf_branch_sample_type {
   	PERF_SAMPLE_BRANCH_NO_FLAGS	= 1U << PERF_SAMPLE_BRANCH_NO_FLAGS_SHIFT,
   	PERF_SAMPLE_BRANCH_NO_CYCLES	= 1U << PERF_SAMPLE_BRANCH_NO_CYCLES_SHIFT,
+	PERF_SAMPLE_BRANCH_TYPE_SAVE	=
+		1U << PERF_SAMPLE_BRANCH_TYPE_SAVE_SHIFT,
+
   	PERF_SAMPLE_BRANCH_MAX		= 1U << PERF_SAMPLE_BRANCH_MAX_SHIFT,
   };
+/*
+ * Common flow change classification
+ */
+enum {
+	PERF_BR_NONE		= 0,		/* unknown */
+	PERF_BR_JCC_FWD		= 1 << 1,	/* conditional forward jump */
+	PERF_BR_JCC_BWD		= 1 << 2,	/* conditional backward jump */
+	PERF_BR_JMP		= 1 << 3,	/* jump */
+	PERF_BR_IND_JMP		= 1 << 4,	/* indirect jump */
+	PERF_BR_CALL		= 1 << 5,	/* call */
+	PERF_BR_IND_CALL	= 1 << 6,	/* indirect call */
+	PERF_BR_RET		= 1 << 7,	/* return */
+	PERF_BR_FAR_BRANCH	= 1 << 8,	/* SYSCALL,SYSRET,IRQ,... */
+};
+
   #define PERF_SAMPLE_BRANCH_PLM_ALL \
   	(PERF_SAMPLE_BRANCH_USER|\
   	 PERF_SAMPLE_BRANCH_KERNEL|\

@@ -999,6 +1019,7 @@ union perf_mem_data_src {
    *     in_tx: running in a hardware transaction
    *     abort: aborting a hardware transaction
    *    cycles: cycles from last branch (or 0 if not supported)
+ *      type: branch type
    */
   struct perf_branch_entry {
   	__u64	from;

@@ -1008,7 +1029,8 @@ struct perf_branch_entry {
   		in_tx:1,    /* in transaction */
   		abort:1,    /* transaction abort */
   		cycles:16,  /* cycle count to last branch */
-		reserved:44;
+		type:9,     /* branch type */
+		reserved:35;
   };
   #endif /* _UAPI_LINUX_PERF_EVENT_H */

Signature · 1 line

2.7.4

Adding the perf kernel maintainers to the CC list.

Em Fri, Mar 31, 2017 at 11:18:38PM +0800, Jin Yao escreveu:

Quoted 19 lines

It is often useful to know the branch types while analyzing branch data. For example, a call is very different from a conditional branch.

Currently we have to look it up in binary while the binary may later not be available and even the binary is available but user has to take some time. It is very useful for user to check it directly in perf report.

Perf already has support for disassembling the branch instruction to get the branch type. The branch type is defined in lbr.c.

To keep consistent on kernel and userspace and make the classification more common, the patch adds the common branch type classification in perf_event.h.

Since the disassembling of branch instruction needs some overhead, a new PERF_SAMPLE_BRANCH_TYPE_SAVE is introduced to indicate if it needs to disassemble the branch instruction and record the branch type.

Quoted 1 line · Arnaldo Carvalho de Melo

Adding the perf kernel maintainers to the CC list.

Thanks.

Quoted 16 lines

Em Fri, Mar 31, 2017 at 11:18:38PM +0800, Jin Yao escreveu:

Quoted 15 lines

It is often useful to know the branch types while analyzing branch data. For example, a call is very different from a conditional branch.

Currently we have to look it up in binary while the binary may later not be available and even the binary is available but user has to take some time. It is very useful for user to check it directly in perf report.

Perf already has support for disassembling the branch instruction to get the branch type. The branch type is defined in lbr.c.

To keep consistent on kernel and userspace and make the classification more common, the patch adds the common branch type classification in perf_event.h.

Quoted 4 lines

Quoted 4 lines

Since the disassembling of branch instruction needs some overhead, a new PERF_SAMPLE_BRANCH_TYPE_SAVE is introduced to indicate if it needs to disassemble the branch instruction and record the branch type.

I don't get it. Why is the kernel interface mucked with for a user-space feature?

That's wrong.

Hi, otherwise we have to maintain 2 branch type copies between kernel and user-space.

For example, currently X86_BR_* are defined in lbr.c. To display the branch type in user-space, the user-space has to maintain the same copy for X86_BR_*. I didn't get a better idea.

Quoted 6 lines · Yao

Hi, otherwise we have to maintain 2 branch type copies between kernel and user-space.

For example, currently X86_BR_* are defined in lbr.c. To display the branch type in user-space, the user-space has to maintain the same copy for X86_BR_*. I didn't get a better idea.

I still don't understand what you want; or why it would matter.

Those specific macros are for hardware LBR filter emulation/fixup. What does that have to do with any userspace crud?

Quoted 11 lines · Peter Zijlstra

Quoted 6 lines · Yao

Hi, otherwise we have to maintain 2 branch type copies between kernel and user-space.

For example, currently X86_BR_* are defined in lbr.c. To display the branch type in user-space, the user-space has to maintain the same copy for X86_BR_*. I didn't get a better idea.

I still don't understand what you want; or why it would matter.

Those specific macros are for hardware LBR filter emulation/fixup. What does that have to do with any userspace crud?

I just want to provide a new feature that the user can directly check branch type
in perf report, instead of looking it up in the binary. Binary could be not available
later, so it's possible that userspace can't get the branch type.

The X86_BR are generated when disassembling the branch instruction in kernel.
They can be considered as the x86 branch types.

It's easy to let kernel return the x86 branch types to userspace, and then userspace
shows the branch type in perf report.

While kernel and userspace have to maintain the X86_BR definitions. One copy is in
kernel and the other copy is in userspace. To avoid the duplicate definitions , I define
the common branch type in perf_event.h to share between kernel and userspace.
That's why I do that.

I just want to provide a new feature that the user can directly check branch type in perf report, instead of looking it up in the binary. Binary could be not available later, so it's possible that userspace can't get the branch type.

The X86_BR are generated when disassembling the branch instruction in kernel. They can be considered as the x86 branch types.

It's easy to let kernel return the x86 branch types to userspace, and then userspace shows the branch type in perf report.

While kernel and userspace have to maintain the X86_BR definitions. One copy is in kernel and the other copy is in userspace. To avoid the duplicate definitions , I define the common branch type in perf_event.h to share between kernel and userspace. That's why I do that.

Argh, fix your mailer. That is unreadable.

/me reflows...

See, that's so much better..

Oh, so you _ARE_ adding a kernel feature? I understood you only wanted to change perf-report.

WTH didn't you Cc the maintainers?

Also, if you do this, you need to Cc the PowerPC people, since they too implement PERF_SAMPLE_BRANCH_ bits.