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Subject[PATCH 2/4] perf record: add HEADER_BRANCH_STACK tag
Date
This patch adds a new feature bit, namely,
HEADER_BRANCH_STACK. When present, it indicates
that sample records may contain branch stack.

This could be useful to a viewer to switch to
branch mode without having to parse all the
samples or without a specific cmdline option.

This will be used in a subsequent patch to
enhance perf report with branch stacks.

Signed-off-by: Stephane Eranian <eranian@google.com>
---
tools/perf/builtin-record.c | 3 +++
tools/perf/util/header.c | 13 +++++++++++++
tools/perf/util/header.h | 2 +-
3 files changed, 17 insertions(+), 1 deletions(-)
diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index a7c53a9..be4e1ee 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -473,6 +473,9 @@ static int __cmd_record(struct perf_record *rec, int argc, const char **argv)
if (!have_tracepoints(&evsel_list->entries))
perf_header__clear_feat(&session->header, HEADER_TRACE_INFO);

+ if (!rec->opts.branch_stack)
+ perf_header__clear_feat(&session->header, HEADER_BRANCH_STACK);
+
if (!rec->file_new) {
err = perf_session__read_header(session, output);
if (err < 0)
diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
index c851495..0d9b6da 100644
--- a/tools/perf/util/header.c
+++ b/tools/perf/util/header.c
@@ -1023,6 +1023,12 @@ static int write_cpuid(int fd, struct perf_header *h __used,
return do_write_string(fd, buffer);
}

+static int write_branch_stack(int fd __used, struct perf_header *h __used,
+ struct perf_evlist *evlist __used)
+{
+ return 0;
+}
+
static void print_hostname(struct perf_header *ph, int fd, FILE *fp)
{
char *str = do_read_string(fd, ph);
@@ -1315,6 +1321,12 @@ static void print_cpuid(struct perf_header *ph, int fd, FILE *fp)
free(str);
}

+static void print_branch_stack(struct perf_header *ph __used, int fd __used,
+ FILE *fp)
+{
+ fprintf(fp, "# contains samples with branch stack\n");
+}
+
static int __event_process_build_id(struct build_id_event *bev,
char *filename,
struct perf_session *session)
@@ -1519,6 +1531,7 @@ static const struct feature_ops feat_ops[HEADER_LAST_FEATURE] = {
FEAT_OPA(HEADER_CMDLINE, cmdline),
FEAT_OPF(HEADER_CPU_TOPOLOGY, cpu_topology),
FEAT_OPF(HEADER_NUMA_TOPOLOGY, numa_topology),
+ FEAT_OPA(HEADER_BRANCH_STACK, branch_stack),
};

struct header_print_data {
diff --git a/tools/perf/util/header.h b/tools/perf/util/header.h
index e68f617..21a6be0 100644
--- a/tools/perf/util/header.h
+++ b/tools/perf/util/header.h
@@ -27,7 +27,7 @@ enum {
HEADER_EVENT_DESC,
HEADER_CPU_TOPOLOGY,
HEADER_NUMA_TOPOLOGY,
-
+ HEADER_BRANCH_STACK,
HEADER_LAST_FEATURE,
HEADER_FEAT_BITS = 256,
};
--
1.7.4.1


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