perf annotate: Save branch counters for each block

When annotating a basic block, it's useful to display the occurrences
of other events in the block.

The branch counter feature is only available for newer Intel platforms.

So a dedicated option to display the branch counters is not introduced.

Reuse the existing --total-cycles option, which triggers the annotation
of a basic block and displays the cycle-related annotation.

When the branch counters information is available, the branch counters
are automatically appended after all the cycle-related annotation.

Accounting the branch counters as well when accounting the cycles in
hist__account_cycles().

In 'struct annotated_branch', introduce a br_cntr array to save the
accumulation of each branch counter.

In a sample, all the branch counters for a branch are saved in a u64
space.

Because the saturation of a branch counter is small, e.g., for Intel
Sierra Forest, the saturation is only 3.

Add ANNOTATION__BR_CNTR_SATURATED_FLAG to indicate if a branch counter
once saturated. That can be used to indicate a potential event lost
because of the saturation.

Reviewed-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Kan Liang <kan.liang@linux.intel.com>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: https://lore.kernel.org/r/20240813160208.2493643-5-kan.liang@linux.intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 56 insertions, 12 deletions

diff --git a/tools/perf/util/annotate.c b/tools/perf/util/annotate.c
index a87d2e97e10d..c269758d47c8 100644
--- a/tools/perf/util/annotate.c
+++ b/tools/perf/util/annotate.c
@@ -266,22 +266,30 @@ struct annotated_branch *annotation__get_branch(struct annotation *notes)
 	return notes->branch;
 }
 
-static struct cyc_hist *symbol__cycles_hist(struct symbol *sym)
+static struct annotated_branch *symbol__find_branch_hist(struct symbol *sym,
+							 unsigned int br_cntr_nr)
 {
 	struct annotation *notes = symbol__annotation(sym);
 	struct annotated_branch *branch;
+	const size_t size = symbol__size(sym);
 
 	branch = annotation__get_branch(notes);
 	if (branch == NULL)
 		return NULL;
 
 	if (branch->cycles_hist == NULL) {
-		const size_t size = symbol__size(sym);
-
 		branch->cycles_hist = calloc(size, sizeof(struct cyc_hist));
+		if (!branch->cycles_hist)
+			return NULL;
+	}
+
+	if (br_cntr_nr && branch->br_cntr == NULL) {
+		branch->br_cntr = calloc(br_cntr_nr * size, sizeof(u64));
+		if (!branch->br_cntr)
+			return NULL;
 	}
 
-	return branch->cycles_hist;
+	return branch;
 }
 
 struct annotated_source *symbol__hists(struct symbol *sym, int nr_hists)
@@ -316,16 +324,44 @@ static int symbol__inc_addr_samples(struct map_symbol *ms,
 	return src ? __symbol__inc_addr_samples(ms, src, evsel->core.idx, addr, sample) : 0;
 }
 
-static int symbol__account_cycles(u64 addr, u64 start,
-				  struct symbol *sym, unsigned cycles)
+static int symbol__account_br_cntr(struct annotated_branch *branch,
+				   struct evsel *evsel,
+				   unsigned offset,
+				   u64 br_cntr)
+{
+	unsigned int br_cntr_nr = evsel__leader(evsel)->br_cntr_nr;
+	unsigned int base = evsel__leader(evsel)->br_cntr_idx;
+	unsigned int width = evsel__env(evsel)->br_cntr_width;
+	unsigned int off = offset * evsel->evlist->nr_br_cntr;
+	unsigned int i, mask = (1L << width) - 1;
+	u64 *branch_br_cntr = branch->br_cntr;
+
+	if (!br_cntr || !branch_br_cntr)
+		return 0;
+
+	for (i = 0; i < br_cntr_nr; i++) {
+		u64 cntr = (br_cntr >> i * width) & mask;
+
+		branch_br_cntr[off + i + base] += cntr;
+		if (cntr == mask)
+			branch_br_cntr[off + i + base] |= ANNOTATION__BR_CNTR_SATURATED_FLAG;
+	}
+
+	return 0;
+}
+
+static int symbol__account_cycles(u64 addr, u64 start, struct symbol *sym,
+				  unsigned cycles, struct evsel *evsel,
+				  u64 br_cntr)
 {
-	struct cyc_hist *cycles_hist;
+	struct annotated_branch *branch;
 	unsigned offset;
+	int ret;
 
 	if (sym == NULL)
 		return 0;
-	cycles_hist = symbol__cycles_hist(sym);
-	if (cycles_hist == NULL)
+	branch = symbol__find_branch_hist(sym, evsel->evlist->nr_br_cntr);
+	if (!branch)
 		return -ENOMEM;
 	if (addr < sym->start || addr >= sym->end)
 		return -ERANGE;
@@ -337,15 +373,22 @@ static int symbol__account_cycles(u64 addr, u64 start,
 			start = 0;
 	}
 	offset = addr - sym->start;
-	return __symbol__account_cycles(cycles_hist,
+	ret = __symbol__account_cycles(branch->cycles_hist,
 					start ? start - sym->start : 0,
 					offset, cycles,
 					!!start);
+
+	if (ret)
+		return ret;
+
+	return symbol__account_br_cntr(branch, evsel, offset, br_cntr);
 }
 
 int addr_map_symbol__account_cycles(struct addr_map_symbol *ams,
 				    struct addr_map_symbol *start,
-				    unsigned cycles)
+				    unsigned cycles,
+				    struct evsel *evsel,
+				    u64 br_cntr)
 {
 	u64 saddr = 0;
 	int err;
@@ -371,7 +414,7 @@ int addr_map_symbol__account_cycles(struct addr_map_symbol *ams,
 			start ? start->addr : 0,
 			ams->ms.sym ? ams->ms.sym->start + map__start(ams->ms.map) : 0,
 			saddr);
-	err = symbol__account_cycles(ams->al_addr, saddr, ams->ms.sym, cycles);
+	err = symbol__account_cycles(ams->al_addr, saddr, ams->ms.sym, cycles, evsel, br_cntr);
 	if (err)
 		pr_debug2("account_cycles failed %d\n", err);
 	return err;
@@ -412,6 +455,7 @@ static void annotated_branch__delete(struct annotated_branch *branch)
 {
 	if (branch) {
 		zfree(&branch->cycles_hist);
+		free(branch->br_cntr);
 		free(branch);
 	}
 }