perf bpf-filter: Split per-task filter use case

If the target is a list of tasks, it can use a shared hash map for
filter expressions.  The key of the filter map is an integer index like
in an array.  A separate pid_hash map is added to get the index for the
filter map using the tgid.

For system-wide mode including per-cpu or per-user targets are handled
by the single entry map like before.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: KP Singh <kpsingh@kernel.org>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Song Liu <song@kernel.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: bpf@vger.kernel.org
Link: https://lore.kernel.org/r/20240703223035.2024586-4-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

2 files changed, 22 insertions, 0 deletions

diff --git a/tools/perf/util/bpf_skel/sample-filter.h b/tools/perf/util/bpf_skel/sample-filter.h
index bb6a1b91f1df..e666bfd5fbdd 100644
--- a/tools/perf/util/bpf_skel/sample-filter.h
+++ b/tools/perf/util/bpf_skel/sample-filter.h
@@ -2,6 +2,7 @@
 #define PERF_UTIL_BPF_SKEL_SAMPLE_FILTER_H
 
 #define MAX_FILTERS  64
+#define MAX_PIDS     (16 * 1024)
 
 /* supported filter operations */
 enum perf_bpf_filter_op {
diff --git a/tools/perf/util/bpf_skel/sample_filter.bpf.c b/tools/perf/util/bpf_skel/sample_filter.bpf.c
index 0d56e52b922c..c5273f06fa45 100644
--- a/tools/perf/util/bpf_skel/sample_filter.bpf.c
+++ b/tools/perf/util/bpf_skel/sample_filter.bpf.c
@@ -15,7 +15,16 @@ struct filters {
 	__uint(max_entries, 1);
 } filters SEC(".maps");
 
+/* tgid to filter index */
+struct pid_hash {
+	__uint(type, BPF_MAP_TYPE_HASH);
+	__type(key, int);
+	__type(value, int);
+	__uint(max_entries, 1);
+} pid_hash SEC(".maps");
+
 int dropped;
+volatile const int use_pid_hash;
 
 void *bpf_cast_to_kern_ctx(void *) __ksym;
 
@@ -184,6 +193,18 @@ int perf_sample_filter(void *ctx)
 	kctx = bpf_cast_to_kern_ctx(ctx);
 
 	k = 0;
+
+	if (use_pid_hash) {
+		int tgid = bpf_get_current_pid_tgid() >> 32;
+		int *idx;
+
+		idx = bpf_map_lookup_elem(&pid_hash, &tgid);
+		if (idx)
+			k = *idx;
+		else
+			goto drop;
+	}
+
 	entry = bpf_map_lookup_elem(&filters, &k);
 	if (entry == NULL)
 		goto drop;