[PATCH 44/91] perf thread-stack: Add thread_stack__br_sample_late()

Arnaldo Carvalho de Melo
2020-05-06T15:25:28Z

From: Adrian Hunter <adrian.hunter@intel.com>

Add a thread stack function to create a branch stack for hardware events
where the sample records get created some time after the event occurred.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Link: http://lore.kernel.org/lkml/20200429150751.12570-7-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
tools/perf/util/thread-stack.c | 104 +++++++++++++++++++++++++++++++++
tools/perf/util/thread-stack.h | 3 +
2 files changed, 107 insertions(+)

diff --git a/tools/perf/util/thread-stack.c b/tools/perf/util/thread-stack.c
index 79698831b4b9..1b992bbba4e8 100644
--- a/tools/perf/util/thread-stack.c
+++ b/tools/perf/util/thread-stack.c
@@ -645,6 +645,110 @@ void thread_stack__br_sample(struct thread *thread, int cpu,
}
}

+/* Start of user space branch entries */
+static bool us_start(struct branch_entry *be, u64 kernel_start, bool *start)
+{
+ if (!*start)
+ *start = be->to && be->to < kernel_start;
+
+ return *start;
+}
+
+/*
+ * Start of branch entries after the ip fell in between 2 branches, or user
+ * space branch entries.
+ */
+static bool ks_start(struct branch_entry *be, u64 sample_ip, u64 kernel_start,
+ bool *start, struct branch_entry *nb)
+{
+ if (!*start) {
+ *start = (nb && sample_ip >= be->to && sample_ip <= nb->from) ||
+ be->from < kernel_start ||
+ (be->to && be->to < kernel_start);
+ }
+
+ return *start;
+}
+
+/*
+ * Hardware sample records, created some time after the event occurred, need to
+ * have subsequent addresses removed from the branch stack.
+ */
+void thread_stack__br_sample_late(struct thread *thread, int cpu,
+ struct branch_stack *dst, unsigned int sz,
+ u64 ip, u64 kernel_start)
+{
+ struct thread_stack *ts = thread__stack(thread, cpu);
+ struct branch_entry *d, *s, *spos, *ssz;
+ struct branch_stack *src;
+ unsigned int nr = 0;
+ bool start = false;
+
+ dst->nr = 0;
+
+ if (!ts)
+ return;
+
+ src = ts->br_stack_rb;
+ if (!src->nr)
+ return;
+
+ spos = &src->entries[ts->br_stack_pos];
+ ssz = &src->entries[ts->br_stack_sz];
+
+ d = &dst->entries[0];
+ s = spos;
+
+ if (ip < kernel_start) {
+ /*
+ * User space sample: start copying branch entries when the
+ * branch is in user space.
+ */
+ for (s = spos; s < ssz && nr < sz; s++) {
+ if (us_start(s, kernel_start, &start)) {
+ *d++ = *s;
+ nr += 1;
+ }
+ }
+
+ if (src->nr >= ts->br_stack_sz) {
+ for (s = &src->entries[0]; s < spos && nr < sz; s++) {
+ if (us_start(s, kernel_start, &start)) {
+ *d++ = *s;
+ nr += 1;
+ }
+ }
+ }
+ } else {
+ struct branch_entry *nb = NULL;
+
+ /*
+ * Kernel space sample: start copying branch entries when the ip
+ * falls in between 2 branches (or the branch is in user space
+ * because then the start must have been missed).
+ */
+ for (s = spos; s < ssz && nr < sz; s++) {
+ if (ks_start(s, ip, kernel_start, &start, nb)) {
+ *d++ = *s;
+ nr += 1;
+ }
+ nb = s;
+ }
+
+ if (src->nr >= ts->br_stack_sz) {
+ for (s = &src->entries[0]; s < spos && nr < sz; s++) {
+ if (ks_start(s, ip, kernel_start, &start, nb)) {
+ *d++ = *s;
+ nr += 1;
+ }
+ nb = s;
+ }
+ }
+ }
+
+ dst->nr = nr;
+}
+
struct call_return_processor *
call_return_processor__new(int (*process)(struct call_return *cr, u64 *parent_db_id, void *data),
void *data)
diff --git a/tools/perf/util/thread-stack.h b/tools/perf/util/thread-stack.h
index c279a0cbbdd0..3bc47a42af8e 100644
--- a/tools/perf/util/thread-stack.h
+++ b/tools/perf/util/thread-stack.h
@@ -91,6 +91,9 @@ void thread_stack__sample_late(struct thread *thread, int cpu,
u64 kernel_start);
void thread_stack__br_sample(struct thread *thread, int cpu,
struct branch_stack *dst, unsigned int sz);
+void thread_stack__br_sample_late(struct thread *thread, int cpu,
+ struct branch_stack *dst, unsigned int sz,
+ u64 sample_ip, u64 kernel_start);
int thread_stack__flush(struct thread *thread);
void thread_stack__free(struct thread *thread);
size_t thread_stack__depth(struct thread *thread, int cpu);
--
2.21.1