[PATCH 5/6] perf lock contention: Support lock addr/name filtering for BPF

Namhyung Kim
2022-12-19T20:18:02Z

Likewise, add addr_filter BPF hash map and check it with the lock
address.

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

Total time: 0.169 [sec]
contended total wait max wait avg wait type caller

18 174.09 us 25.31 us 9.67 us rwlock:W do_exit+0x36d
5 32.34 us 10.87 us 6.47 us rwlock:R do_wait+0x8b
4 15.41 us 4.73 us 3.85 us rwlock:W release_task+0x6e

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
---
tools/perf/util/bpf_lock_contention.c | 42 ++++++++++++++++++-
.../perf/util/bpf_skel/lock_contention.bpf.c | 17 ++++++++
2 files changed, 58 insertions(+), 1 deletion(-)

diff --git a/tools/perf/util/bpf_lock_contention.c b/tools/perf/util/bpf_lock_contention.c
index b8590b82ad3d..4a95c0ebcb3c 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, ntypes = 1;
+ int ncpus = 1, ntasks = 1, ntypes = 1, naddrs = 1;
struct evlist *evlist = con->evlist;
struct target *target = con->target;

@@ -49,9 +49,39 @@ int lock_contention_prepare(struct lock_contention *con)
if (con->filters->nr_types)
ntypes = con->filters->nr_types;

+ /* resolve lock name filters to addr */
+ if (con->filters->nr_syms) {
+ struct symbol *sym;
+ struct map *kmap;
+ unsigned long *addrs;
+
+ for (i = 0; i < con->filters->nr_syms; i++) {
+ sym = machine__find_kernel_symbol_by_name(con->machine,
+ con->filters->syms[i],
+ &kmap);
+ if (sym == NULL) {
+ pr_warning("ignore unknown symbol: %s\n",
+ con->filters->syms[i]);
+ continue;
+ }
+
+ addrs = realloc(con->filters->addrs,
+ (con->filters->nr_addrs + 1) * sizeof(*addrs));
+ if (addrs == NULL) {
+ pr_warning("memory allocation failure\n");
+ continue;
+ }
+
+ addrs[con->filters->nr_addrs++] = kmap->unmap_ip(kmap, sym->start);
+ con->filters->addrs = addrs;
+ }
+ naddrs = con->filters->nr_addrs;
+ }
+
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);
+ bpf_map__set_max_entries(skel->maps.addr_filter, naddrs);

if (lock_contention_bpf__load(skel) < 0) {
pr_err("Failed to load lock-contention BPF skeleton\n");
@@ -103,6 +133,16 @@ int lock_contention_prepare(struct lock_contention *con)
bpf_map_update_elem(fd, &con->filters->types[i], &val, BPF_ANY);
}

+ if (con->filters->nr_addrs) {
+ u8 val = 1;
+
+ skel->bss->has_addr = 1;
+ fd = bpf_map__fd(skel->maps.addr_filter);
+
+ for (i = 0; i < con->filters->nr_addrs; i++)
+ bpf_map_update_elem(fd, &con->filters->addrs[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 fb0128de7c00..ad0ca5d50557 100644
--- a/tools/perf/util/bpf_skel/lock_contention.bpf.c
+++ b/tools/perf/util/bpf_skel/lock_contention.bpf.c
@@ -69,11 +69,19 @@ struct {
__uint(max_entries, 1);
} type_filter SEC(".maps");

+struct {
+ __uint(type, BPF_MAP_TYPE_HASH);
+ __uint(key_size, sizeof(__u64));
+ __uint(value_size, sizeof(__u8));
+ __uint(max_entries, 1);
+} addr_filter SEC(".maps");
+
/* control flags */
int enabled;
int has_cpu;
int has_task;
int has_type;
+int has_addr;
int stack_skip;

/* determine the key of lock stat */
@@ -111,6 +119,15 @@ static inline int can_record(u64 *ctx)
return 0;
}

+ if (has_addr) {
+ __u8 *ok;
+ __u64 addr = ctx[0];
+
+ ok = bpf_map_lookup_elem(&addr_filter, &addr);
+ if (!ok)
+ return 0;
+ }
+
return 1;
}

--
2.39.0.314.g84b9a713c41-goog