[PATCH v2 0/3] tools perf: Add branch speculation info

linux-perf-users.vger.kernel.org archive mirror
 help / color / mirror / Atom feed

* [PATCH v2 0/3] tools perf: Add branch speculation info
@ 2022-09-28 10:59 Sandipan Das
  2022-09-28 10:59 ` [PATCH v2 1/3] tools headers uapi: Sync perf_event.h with kernel sources Sandipan Das
                   ` (2 more replies)
  0 siblings, 3 replies; 4+ messages in thread
From: Sandipan Das @ 2022-09-28 10:59 UTC (permalink / raw)
  To: linux-kernel, linux-perf-users, x86
  Cc: peterz, bp, acme, namhyung, jolsa, tglx, mingo, mark.rutland,
	alexander.shishkin, dave.hansen, like.xu.linux, eranian,
	ananth.narayan, ravi.bangoria, santosh.shukla, sandipan.das

AMD Last Branch Record Extension Version 2 (LbrExtV2) provides branch
speculation information and the perf UAPI is extended to provide this in
a generic way. Update the tools headers and perf tool to be able to show
this additional information.

The LbrExtV2 enablement and UAPI changes can be found at:
https://lore.kernel.org/all/cover.1660211399.git.sandipan.das@amd.com/

Previous versions can be found at:
v1: https://lore.kernel.org/all/cover.1660217326.git.sandipan.das@amd.com/

Changes in v2:
- Drop msr-index.h related changes for now.
- Rebase on top of latest perf/core.
- Fix UAPI breakage introduced by the ARM64 BRBE changes to perf branch
  entry.

Sandipan Das (3):
  tools headers uapi: Sync perf_event.h with kernel sources
  perf script: Show branch speculation info
  perf session: Show branch speculation info in raw dump

 tools/include/uapi/linux/perf_event.h | 15 ++++++++++++++-
 tools/perf/builtin-script.c           |  5 +++--
 tools/perf/util/branch.c              | 15 +++++++++++++++
 tools/perf/util/branch.h              |  5 ++++-
 tools/perf/util/evsel.c               | 15 ++++++++++++---
 tools/perf/util/session.c             |  5 +++--
 6 files changed, 51 insertions(+), 9 deletions(-)

-- 
2.34.1


^ permalink raw reply	[flat|nested] 4+ messages in thread

* [PATCH v2 1/3] tools headers uapi: Sync perf_event.h with kernel sources
  2022-09-28 10:59 [PATCH v2 0/3] tools perf: Add branch speculation info Sandipan Das
@ 2022-09-28 10:59 ` Sandipan Das
  2022-09-28 10:59 ` [PATCH v2 2/3] perf script: Show branch speculation info Sandipan Das
  2022-09-28 10:59 ` [PATCH v2 3/3] perf session: Show branch speculation info in raw dump Sandipan Das
  2 siblings, 0 replies; 4+ messages in thread
From: Sandipan Das @ 2022-09-28 10:59 UTC (permalink / raw)
  To: linux-kernel, linux-perf-users, x86
  Cc: peterz, bp, acme, namhyung, jolsa, tglx, mingo, mark.rutland,
	alexander.shishkin, dave.hansen, like.xu.linux, eranian,
	ananth.narayan, ravi.bangoria, santosh.shukla, sandipan.das

Sync perf_event.h with the kernel sources by adding the new "spec" bitfield
to branch entries.

Signed-off-by: Sandipan Das <sandipan.das@amd.com>
---
 tools/include/uapi/linux/perf_event.h | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/tools/include/uapi/linux/perf_event.h b/tools/include/uapi/linux/perf_event.h
index 49cb2355efc0..9e1ae54b48a2 100644
--- a/tools/include/uapi/linux/perf_event.h
+++ b/tools/include/uapi/linux/perf_event.h
@@ -263,6 +263,17 @@ enum {
 	PERF_BR_MAX,
 };
 
+/*
+ * Common branch speculation outcome classification
+ */
+enum {
+	PERF_BR_SPEC_NA			= 0,	/* Not available */
+	PERF_BR_SPEC_WRONG_PATH		= 1,	/* Speculative but on wrong path */
+	PERF_BR_NON_SPEC_CORRECT_PATH	= 2,	/* Non-speculative but on correct path */
+	PERF_BR_SPEC_CORRECT_PATH	= 3,	/* Speculative and on correct path */
+	PERF_BR_SPEC_MAX,
+};
+
 enum {
 	PERF_BR_NEW_FAULT_ALGN		= 0,    /* Alignment fault */
 	PERF_BR_NEW_FAULT_DATA		= 1,    /* Data fault */
@@ -1395,6 +1406,7 @@ union perf_mem_data_src {
  *     abort: aborting a hardware transaction
  *    cycles: cycles from last branch (or 0 if not supported)
  *      type: branch type
+ *      spec: branch speculation info (or 0 if not supported)
  */
 struct perf_branch_entry {
 	__u64	from;
@@ -1405,9 +1417,10 @@ struct perf_branch_entry {
 		abort:1,    /* transaction abort */
 		cycles:16,  /* cycle count to last branch */
 		type:4,     /* branch type */
+		spec:2,     /* branch speculation info */
 		new_type:4, /* additional branch type */
 		priv:3,     /* privilege level */
-		reserved:33;
+		reserved:31;
 };
 
 union perf_sample_weight {
-- 
2.34.1


^ permalink raw reply related	[flat|nested] 4+ messages in thread

* [PATCH v2 2/3] perf script: Show branch speculation info
  2022-09-28 10:59 [PATCH v2 0/3] tools perf: Add branch speculation info Sandipan Das
  2022-09-28 10:59 ` [PATCH v2 1/3] tools headers uapi: Sync perf_event.h with kernel sources Sandipan Das
@ 2022-09-28 10:59 ` Sandipan Das
  2022-09-28 10:59 ` [PATCH v2 3/3] perf session: Show branch speculation info in raw dump Sandipan Das
  2 siblings, 0 replies; 4+ messages in thread
From: Sandipan Das @ 2022-09-28 10:59 UTC (permalink / raw)
  To: linux-kernel, linux-perf-users, x86
  Cc: peterz, bp, acme, namhyung, jolsa, tglx, mingo, mark.rutland,
	alexander.shishkin, dave.hansen, like.xu.linux, eranian,
	ananth.narayan, ravi.bangoria, santosh.shukla, sandipan.das

Show the branch speculation info if provided by the branch recording
hardware feature. This can be useful for optimizing code further.

The speculation info is appended to the end of the list of fields so any
existing tools that use "/" as a delimiter for access fields via an index
remain unaffected. Also show "-" instead of "N/A" when speculation info
is unavailable because "/" is used as the field separator.

E.g.

  $ perf record -j any,u,save_type ./test_branch
  $ perf script --fields brstacksym

Before:

  [...]
  check_match+0x60/strcmp+0x0/P/-/-/0/CALL
  do_lookup_x+0x3c5/check_match+0x0/P/-/-/0/CALL
  [...]

After:

  [...]
  check_match+0x60/strcmp+0x0/P/-/-/0/CALL/NON_SPEC_CORRECT_PATH
  do_lookup_x+0x3c5/check_match+0x0/P/-/-/0/CALL/NON_SPEC_CORRECT_PATH
  [...]

Signed-off-by: Sandipan Das <sandipan.das@amd.com>
---
 tools/perf/builtin-script.c |  5 +++--
 tools/perf/util/branch.c    | 15 +++++++++++++++
 tools/perf/util/branch.h    |  5 ++++-
 tools/perf/util/evsel.c     | 15 ++++++++++++---
 4 files changed, 34 insertions(+), 6 deletions(-)

diff --git a/tools/perf/builtin-script.c b/tools/perf/builtin-script.c
index 886f53cfa257..5b337f47a4be 100644
--- a/tools/perf/builtin-script.c
+++ b/tools/perf/builtin-script.c
@@ -877,12 +877,13 @@ mispred_str(struct branch_entry *br)
 
 static int print_bstack_flags(FILE *fp, struct branch_entry *br)
 {
-	return fprintf(fp, "/%c/%c/%c/%d/%s ",
+	return fprintf(fp, "/%c/%c/%c/%d/%s/%s ",
 		       mispred_str(br),
 		       br->flags.in_tx ? 'X' : '-',
 		       br->flags.abort ? 'A' : '-',
 		       br->flags.cycles,
-		       get_branch_type(br));
+		       get_branch_type(br),
+		       br->flags.spec ? branch_spec_desc(br->flags.spec) : "-");
 }
 
 static int perf_sample__fprintf_brstack(struct perf_sample *sample,
diff --git a/tools/perf/util/branch.c b/tools/perf/util/branch.c
index 6d38238481d3..378f16a24751 100644
--- a/tools/perf/util/branch.c
+++ b/tools/perf/util/branch.c
@@ -212,3 +212,18 @@ int branch_type_str(struct branch_type_stat *st, char *bf, int size)
 
 	return printed;
 }
+
+const char *branch_spec_desc(int spec)
+{
+	const char *branch_spec_outcomes[PERF_BR_SPEC_MAX] = {
+		"N/A",
+		"SPEC_WRONG_PATH",
+		"NON_SPEC_CORRECT_PATH",
+		"SPEC_CORRECT_PATH",
+	};
+
+	if (spec >= 0 && spec < PERF_BR_SPEC_MAX)
+		return branch_spec_outcomes[spec];
+
+	return NULL;
+}
diff --git a/tools/perf/util/branch.h b/tools/perf/util/branch.h
index f838b23db180..264817c96560 100644
--- a/tools/perf/util/branch.h
+++ b/tools/perf/util/branch.h
@@ -24,9 +24,10 @@ struct branch_flags {
 			u64 abort:1;
 			u64 cycles:16;
 			u64 type:4;
+			u64 spec:2;
 			u64 new_type:4;
 			u64 priv:3;
-			u64 reserved:33;
+			u64 reserved:31;
 		};
 	};
 };
@@ -90,4 +91,6 @@ const char *get_branch_type(struct branch_entry *e);
 void branch_type_stat_display(FILE *fp, struct branch_type_stat *st);
 int branch_type_str(struct branch_type_stat *st, char *bf, int bfsize);
 
+const char *branch_spec_desc(int spec);
+
 #endif /* _PERF_BRANCH_H */
diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index 5776bfa70f11..0266e885acb6 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -2326,7 +2326,10 @@ u64 evsel__bitfield_swap_branch_flags(u64 value)
 	 * 		abort:1		//transaction abort
 	 * 		cycles:16	//cycle count to last branch
 	 * 		type:4		//branch type
-	 * 		reserved:40
+	 * 		spec:2		//branch speculation info
+	 * 		new_type:4	//additional branch type
+	 * 		priv:3		//privilege level
+	 * 		reserved:31
 	 * 	}
 	 * }
 	 *
@@ -2345,7 +2348,10 @@ u64 evsel__bitfield_swap_branch_flags(u64 value)
 		new_val |= bitfield_swap(value, 3, 1);
 		new_val |= bitfield_swap(value, 4, 16);
 		new_val |= bitfield_swap(value, 20, 4);
-		new_val |= bitfield_swap(value, 24, 40);
+		new_val |= bitfield_swap(value, 24, 2);
+		new_val |= bitfield_swap(value, 26, 4);
+		new_val |= bitfield_swap(value, 30, 3);
+		new_val |= bitfield_swap(value, 33, 31);
 	} else {
 		new_val = bitfield_swap(value, 63, 1);
 		new_val |= bitfield_swap(value, 62, 1);
@@ -2353,7 +2359,10 @@ u64 evsel__bitfield_swap_branch_flags(u64 value)
 		new_val |= bitfield_swap(value, 60, 1);
 		new_val |= bitfield_swap(value, 44, 16);
 		new_val |= bitfield_swap(value, 40, 4);
-		new_val |= bitfield_swap(value, 0, 40);
+		new_val |= bitfield_swap(value, 38, 2);
+		new_val |= bitfield_swap(value, 34, 4);
+		new_val |= bitfield_swap(value, 31, 3);
+		new_val |= bitfield_swap(value, 0, 31);
 	}
 
 	return new_val;
-- 
2.34.1


^ permalink raw reply related	[flat|nested] 4+ messages in thread

* [PATCH v2 3/3] perf session: Show branch speculation info in raw dump
  2022-09-28 10:59 [PATCH v2 0/3] tools perf: Add branch speculation info Sandipan Das
  2022-09-28 10:59 ` [PATCH v2 1/3] tools headers uapi: Sync perf_event.h with kernel sources Sandipan Das
  2022-09-28 10:59 ` [PATCH v2 2/3] perf script: Show branch speculation info Sandipan Das
@ 2022-09-28 10:59 ` Sandipan Das
  2 siblings, 0 replies; 4+ messages in thread
From: Sandipan Das @ 2022-09-28 10:59 UTC (permalink / raw)
  To: linux-kernel, linux-perf-users, x86
  Cc: peterz, bp, acme, namhyung, jolsa, tglx, mingo, mark.rutland,
	alexander.shishkin, dave.hansen, like.xu.linux, eranian,
	ananth.narayan, ravi.bangoria, santosh.shukla, sandipan.das

Show the branch speculation info if provided by the branch recording
hardware feature. This can be useful for purposes of code optimization.

E.g.

  $ perf record -j any,u ./test_branch
  $ perf report --dump-raw-trace

Before:

  [...]
  8380958377610 0x40b178 [0x1b0]: PERF_RECORD_SAMPLE(IP, 0x2): 7952/7952: 0x4f851a period: 48973 addr: 0
  ... branch stack: nr:16
  .....  0: 00000000004b52fd -> 00000000004f82c0 0 cycles  P   0
  .....  1: ffffffff8220137c -> 00000000004b52f0 0 cycles M    0
  .....  2: 000000000041d1c4 -> 00000000004b52f0 0 cycles  P   0
  .....  3: 00000000004e7ead -> 000000000041d1b0 0 cycles M    0
  .....  4: 00000000004e7f91 -> 00000000004e7ead 0 cycles  P   0
  .....  5: 00000000004e7ea8 -> 00000000004e7f70 0 cycles  P   0
  .....  6: 00000000004e7e52 -> 00000000004e7e98 0 cycles M    0
  .....  7: 00000000004e7e1f -> 00000000004e7e40 0 cycles M    0
  .....  8: 00000000004e7f60 -> 00000000004e7df0 0 cycles  P   0
  .....  9: 00000000004e7f58 -> 00000000004e7f60 0 cycles M    0
  ..... 10: 000000000041d85d -> 00000000004e7f50 0 cycles  P   0
  ..... 11: 000000000043306a -> 000000000041d840 0 cycles  P   0
  ..... 12: ffffffff8220137c -> 0000000000433040 0 cycles M    0
  ..... 13: 000000000041e4a1 -> 0000000000433040 0 cycles  P   0
  ..... 14: ffffffff8220137c -> 000000000041e490 0 cycles M    0
  ..... 15: 000000000041d89b -> 000000000041e487 0 cycles  P   0
   ... thread: test_branch:7952
   ...... dso: /data/sandipan/test_branch
  [...]

After:

  [...]
  8380958377610 0x40b178 [0x1b0]: PERF_RECORD_SAMPLE(IP, 0x2): 7952/7952: 0x4f851a period: 48973 addr: 0
  ... branch stack: nr:16
  .....  0: 00000000004b52fd -> 00000000004f82c0 0 cycles  P   0  NON_SPEC_CORRECT_PATH
  .....  1: ffffffff8220137c -> 00000000004b52f0 0 cycles M    0  NON_SPEC_CORRECT_PATH
  .....  2: 000000000041d1c4 -> 00000000004b52f0 0 cycles  P   0  NON_SPEC_CORRECT_PATH
  .....  3: 00000000004e7ead -> 000000000041d1b0 0 cycles M    0  NON_SPEC_CORRECT_PATH
  .....  4: 00000000004e7f91 -> 00000000004e7ead 0 cycles  P   0  NON_SPEC_CORRECT_PATH
  .....  5: 00000000004e7ea8 -> 00000000004e7f70 0 cycles  P   0  NON_SPEC_CORRECT_PATH
  .....  6: 00000000004e7e52 -> 00000000004e7e98 0 cycles M    0  SPEC_CORRECT_PATH
  .....  7: 00000000004e7e1f -> 00000000004e7e40 0 cycles M    0  NON_SPEC_CORRECT_PATH
  .....  8: 00000000004e7f60 -> 00000000004e7df0 0 cycles  P   0  NON_SPEC_CORRECT_PATH
  .....  9: 00000000004e7f58 -> 00000000004e7f60 0 cycles M    0  NON_SPEC_CORRECT_PATH
  ..... 10: 000000000041d85d -> 00000000004e7f50 0 cycles  P   0  NON_SPEC_CORRECT_PATH
  ..... 11: 000000000043306a -> 000000000041d840 0 cycles  P   0  NON_SPEC_CORRECT_PATH
  ..... 12: ffffffff8220137c -> 0000000000433040 0 cycles M    0  NON_SPEC_CORRECT_PATH
  ..... 13: 000000000041e4a1 -> 0000000000433040 0 cycles  P   0  NON_SPEC_CORRECT_PATH
  ..... 14: ffffffff8220137c -> 000000000041e490 0 cycles M    0  NON_SPEC_CORRECT_PATH
  ..... 15: 000000000041d89b -> 000000000041e487 0 cycles  P   0  NON_SPEC_CORRECT_PATH
   ... thread: test_branch:7952
   ...... dso: /data/sandipan/test_branch
  [...]

Signed-off-by: Sandipan Das <sandipan.das@amd.com>
---
 tools/perf/util/session.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c
index 1a4f10de29ff..71951db535f8 100644
--- a/tools/perf/util/session.c
+++ b/tools/perf/util/session.c
@@ -1177,7 +1177,7 @@ static void branch_stack__printf(struct perf_sample *sample, bool callstack)
 		struct branch_entry *e = &entries[i];
 
 		if (!callstack) {
-			printf("..... %2"PRIu64": %016" PRIx64 " -> %016" PRIx64 " %hu cycles %s%s%s%s %x %s\n",
+			printf("..... %2"PRIu64": %016" PRIx64 " -> %016" PRIx64 " %hu cycles %s%s%s%s %x %s %s\n",
 				i, e->from, e->to,
 				(unsigned short)e->flags.cycles,
 				e->flags.mispred ? "M" : " ",
@@ -1185,7 +1185,8 @@ static void branch_stack__printf(struct perf_sample *sample, bool callstack)
 				e->flags.abort ? "A" : " ",
 				e->flags.in_tx ? "T" : " ",
 				(unsigned)e->flags.reserved,
-				get_branch_type(e));
+				get_branch_type(e),
+				e->flags.spec ? branch_spec_desc(e->flags.spec) : "");
 		} else {
 			if (i == 0) {
 				printf("..... %2"PRIu64": %016" PRIx64 "\n"
-- 
2.34.1


^ permalink raw reply related	[flat|nested] 4+ messages in thread

end of thread, other threads:[~2022-09-28 11:03 UTC | newest]

Thread overview: 4+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2022-09-28 10:59 [PATCH v2 0/3] tools perf: Add branch speculation info Sandipan Das
2022-09-28 10:59 ` [PATCH v2 1/3] tools headers uapi: Sync perf_event.h with kernel sources Sandipan Das
2022-09-28 10:59 ` [PATCH v2 2/3] perf script: Show branch speculation info Sandipan Das
2022-09-28 10:59 ` [PATCH v2 3/3] perf session: Show branch speculation info in raw dump Sandipan Das

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).