[PATCH v3 1/5] perf lock: Add bpf maps for owner stack tracing

[Chun-Tse Shao]

Add a struct and few bpf maps in order to tracing owner stack.
`struct owner_tracing_data`: Contains owner's pid, stack id, timestamp for
  when the owner acquires lock, and the count of lock waiters.
`stack_buf`: Percpu buffer for retrieving owner stacktrace.
`owner_stacks`: For tracing owner stacktrace to customized owner stack id.
`owner_data`: For tracing lock_address to `struct owner_tracing_data` in
  bpf program.
`owner_stat`: For reporting owner stacktrace in usermode.

Signed-off-by: Chun-Tse Shao <ctshao@xxxxxxxxxx>
---
 tools/perf/util/bpf_lock_contention.c         | 16 +++++--
 .../perf/util/bpf_skel/lock_contention.bpf.c  | 42 ++++++++++++++++---
 tools/perf/util/bpf_skel/lock_data.h          |  7 ++++
 3 files changed, 57 insertions(+), 8 deletions(-)

diff --git a/tools/perf/util/bpf_lock_contention.c b/tools/perf/util/bpf_lock_contention.c
index fc8666222399..795e2374facc 100644
--- a/tools/perf/util/bpf_lock_contention.c
+++ b/tools/perf/util/bpf_lock_contention.c
@@ -131,9 +131,19 @@ int lock_contention_prepare(struct lock_contention *con)
 	else
 		bpf_map__set_max_entries(skel->maps.task_data, 1);
 
-	if (con->save_callstack)
-		bpf_map__set_max_entries(skel->maps.stacks, con->map_nr_entries);
-	else
+	if (con->save_callstack) {
+		bpf_map__set_max_entries(skel->maps.stacks,
+					 con->map_nr_entries);
+		if (con->owner) {
+			bpf_map__set_value_size(skel->maps.stack_buf, con->max_stack * sizeof(u64));
+			bpf_map__set_key_size(skel->maps.owner_stacks,
+						con->max_stack * sizeof(u64));
+			bpf_map__set_max_entries(skel->maps.owner_stacks, con->map_nr_entries);
+			bpf_map__set_max_entries(skel->maps.owner_data, con->map_nr_entries);
+			bpf_map__set_max_entries(skel->maps.owner_stat, con->map_nr_entries);
+			skel->rodata->max_stack = con->max_stack;
+		}
+	} else
 		bpf_map__set_max_entries(skel->maps.stacks, 1);
 
 	if (target__has_cpu(target)) {
diff --git a/tools/perf/util/bpf_skel/lock_contention.bpf.c b/tools/perf/util/bpf_skel/lock_contention.bpf.c
index 6533ea9b044c..b4961dd86222 100644
--- a/tools/perf/util/bpf_skel/lock_contention.bpf.c
+++ b/tools/perf/util/bpf_skel/lock_contention.bpf.c
@@ -19,13 +19,37 @@
 #define LCB_F_PERCPU	(1U << 4)
 #define LCB_F_MUTEX	(1U << 5)
 
-/* callstack storage  */
+ /* buffer for owner stacktrace */
 struct {
-	__uint(type, BPF_MAP_TYPE_STACK_TRACE);
+	__uint(type, BPF_MAP_TYPE_PERCPU_ARRAY);
 	__uint(key_size, sizeof(__u32));
 	__uint(value_size, sizeof(__u64));
-	__uint(max_entries, MAX_ENTRIES);
-} stacks SEC(".maps");
+	__uint(max_entries, 1);
+} stack_buf SEC(".maps");
+
+/* a map for tracing owner stacktrace to owner stack id */
+struct {
+	__uint(type, BPF_MAP_TYPE_HASH);
+	__uint(key_size, sizeof(__u64)); // owner stacktrace
+	__uint(value_size, sizeof(__u64)); // owner stack id
+	__uint(max_entries, 1);
+} owner_stacks SEC(".maps");
+
+/* a map for tracing lock address to owner data */
+struct {
+	__uint(type, BPF_MAP_TYPE_HASH);
+	__uint(key_size, sizeof(__u64)); // lock address
+	__uint(value_size, sizeof(struct owner_tracing_data));
+	__uint(max_entries, 1);
+} owner_data SEC(".maps");
+
+/* a map for contention_key (stores owner stack id) to contention data */
+struct {
+	__uint(type, BPF_MAP_TYPE_HASH);
+	__uint(key_size, sizeof(struct contention_key));
+	__uint(value_size, sizeof(struct contention_data));
+	__uint(max_entries, 1);
+} owner_stat SEC(".maps");
 
 /* maintain timestamp at the beginning of contention */
 struct {
@@ -43,6 +67,14 @@ struct {
 	__uint(max_entries, 1);
 } tstamp_cpu SEC(".maps");
 
+/* callstack storage  */
+struct {
+	__uint(type, BPF_MAP_TYPE_STACK_TRACE);
+	__uint(key_size, sizeof(__u32));
+	__uint(value_size, sizeof(__u64));
+	__uint(max_entries, MAX_ENTRIES);
+} stacks SEC(".maps");
+
 /* actual lock contention statistics */
 struct {
 	__uint(type, BPF_MAP_TYPE_HASH);
@@ -143,6 +175,7 @@ const volatile int needs_callstack;
 const volatile int stack_skip;
 const volatile int lock_owner;
 const volatile int use_cgroup_v2;
+const volatile int max_stack;
 
 /* determine the key of lock stat */
 const volatile int aggr_mode;
@@ -466,7 +499,6 @@ int contention_end(u64 *ctx)
 			return 0;
 		need_delete = true;
 	}
-
 	duration = bpf_ktime_get_ns() - pelem->timestamp;
 	if ((__s64)duration < 0) {
 		__sync_fetch_and_add(&time_fail, 1);
diff --git a/tools/perf/util/bpf_skel/lock_data.h b/tools/perf/util/bpf_skel/lock_data.h
index c15f734d7fc4..15f5743bd409 100644
--- a/tools/perf/util/bpf_skel/lock_data.h
+++ b/tools/perf/util/bpf_skel/lock_data.h
@@ -3,6 +3,13 @@
 #ifndef UTIL_BPF_SKEL_LOCK_DATA_H
 #define UTIL_BPF_SKEL_LOCK_DATA_H
 
+struct owner_tracing_data {
+	u32 pid; // Who has the lock.
+	u32 count; // How many waiters for this lock.
+	u64 timestamp; // The time while the owner acquires lock and contention is going on.
+	s32 stack_id; // Identifier for `owner_stat`, which stores as value in `owner_stacks`
+};
+
 struct tstamp_data {
 	u64 timestamp;
 	u64 lock;
-- 
2.48.1.262.g85cc9f2d1e-goog