[PATCH 3/6] perf lock contention: Support lock type filtering for BPF

Namhyung Kim
2022-12-19T20:17:46Z

Likewise, add type_filter BPF hash map and check it when user gave a
lock type filter.

$ sudo ./perf lock con -ab -Y rwlock -- ./perf bench sched messaging
# Running 'sched/messaging' benchmark:
# 20 sender and receiver processes per group
# 10 groups == 400 processes run

Total time: 0.203 [sec]
contended total wait max wait avg wait type caller

15 156.19 us 19.45 us 10.41 us rwlock:W do_exit+0x36d
1 11.12 us 11.12 us 11.12 us rwlock:R do_wait+0x8b
1 5.09 us 5.09 us 5.09 us rwlock:W release_task+0x6e

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
---
tools/perf/builtin-lock.c | 1 +
tools/perf/util/bpf_lock_contention.c | 15 ++++++++++++-
.../perf/util/bpf_skel/lock_contention.bpf.c | 21 +++++++++++++++++--
tools/perf/util/lock-contention.h | 1 +
4 files changed, 35 insertions(+), 3 deletions(-)

diff --git a/tools/perf/builtin-lock.c b/tools/perf/builtin-lock.c
index 49b4add53204..e4e785d3b4ec 100644
--- a/tools/perf/builtin-lock.c
+++ b/tools/perf/builtin-lock.c
@@ -1689,6 +1689,7 @@ static int __cmd_contention(int argc, const char **argv)
.map_nr_entries = bpf_map_entries,
.max_stack = max_stack_depth,
.stack_skip = stack_skip,
+ .filters = &filters,
};

session = perf_session__new(use_bpf ? NULL : &data, &eops);
diff --git a/tools/perf/util/bpf_lock_contention.c b/tools/perf/util/bpf_lock_contention.c
index 8e1b791dc58f..b8590b82ad3d 100644
--- a/tools/perf/util/bpf_lock_contention.c
+++ b/tools/perf/util/bpf_lock_contention.c
@@ -20,7 +20,7 @@ static struct lock_contention_bpf *skel;
int lock_contention_prepare(struct lock_contention *con)
{
int i, fd;
- int ncpus = 1, ntasks = 1;
+ int ncpus = 1, ntasks = 1, ntypes = 1;
struct evlist *evlist = con->evlist;
struct target *target = con->target;

@@ -46,9 +46,12 @@ int lock_contention_prepare(struct lock_contention *con)
ncpus = perf_cpu_map__nr(evlist->core.user_requested_cpus);
if (target__has_task(target))
ntasks = perf_thread_map__nr(evlist->core.threads);
+ if (con->filters->nr_types)
+ ntypes = con->filters->nr_types;

bpf_map__set_max_entries(skel->maps.cpu_filter, ncpus);
bpf_map__set_max_entries(skel->maps.task_filter, ntasks);
+ bpf_map__set_max_entries(skel->maps.type_filter, ntypes);

if (lock_contention_bpf__load(skel) < 0) {
pr_err("Failed to load lock-contention BPF skeleton\n");
@@ -90,6 +93,16 @@ int lock_contention_prepare(struct lock_contention *con)
bpf_map_update_elem(fd, &pid, &val, BPF_ANY);
}

+ if (con->filters->nr_types) {
+ u8 val = 1;
+
+ skel->bss->has_type = 1;
+ fd = bpf_map__fd(skel->maps.type_filter);
+
+ for (i = 0; i < con->filters->nr_types; i++)
+ bpf_map_update_elem(fd, &con->filters->types[i], &val, BPF_ANY);
+ }
+
/* these don't work well if in the rodata section */
skel->bss->stack_skip = con->stack_skip;
skel->bss->aggr_mode = con->aggr_mode;
diff --git a/tools/perf/util/bpf_skel/lock_contention.bpf.c b/tools/perf/util/bpf_skel/lock_contention.bpf.c
index 11b0fc7ee53b..fb0128de7c00 100644
--- a/tools/perf/util/bpf_skel/lock_contention.bpf.c
+++ b/tools/perf/util/bpf_skel/lock_contention.bpf.c
@@ -62,10 +62,18 @@ struct {
__uint(max_entries, 1);
} task_filter SEC(".maps");

+struct {
+ __uint(type, BPF_MAP_TYPE_HASH);
+ __uint(key_size, sizeof(__u32));
+ __uint(value_size, sizeof(__u8));
+ __uint(max_entries, 1);
+} type_filter SEC(".maps");
+
/* control flags */
int enabled;
int has_cpu;
int has_task;
+int has_type;
int stack_skip;

/* determine the key of lock stat */
@@ -74,7 +82,7 @@ int aggr_mode;
/* error stat */
int lost;

-static inline int can_record(void)
+static inline int can_record(u64 *ctx)
{
if (has_cpu) {
__u32 cpu = bpf_get_smp_processor_id();
@@ -94,6 +102,15 @@ static inline int can_record(void)
return 0;
}

+ if (has_type) {
+ __u8 *ok;
+ __u32 flags = (__u32)ctx[1];
+
+ ok = bpf_map_lookup_elem(&type_filter, &flags);
+ if (!ok)
+ return 0;
+ }
+
return 1;
}

@@ -116,7 +133,7 @@ int contention_begin(u64 *ctx)
__u32 pid;
struct tstamp_data *pelem;

- if (!enabled || !can_record())
+ if (!enabled || !can_record(ctx))
return 0;

pid = bpf_get_current_pid_tgid();
diff --git a/tools/perf/util/lock-contention.h b/tools/perf/util/lock-contention.h
index d5b75b222d8e..dc621386a16b 100644
--- a/tools/perf/util/lock-contention.h
+++ b/tools/perf/util/lock-contention.h
@@ -118,6 +118,7 @@ struct lock_contention {
struct target *target;
struct machine *machine;
struct hlist_head *result;
+ struct lock_filter *filters;
unsigned long map_nr_entries;
int lost;
int max_stack;
--
2.39.0.314.g84b9a713c41-goog