Delay map cleanup in bpf (#682)

* delay map cleanup in bpf

* add changelog entry

CHANGELOG.md

@@ -20,6 +20,7 @@ OpenTelemetry Go Automatic Instrumentation adheres to [Semantic Versioning](http
 - Clean up warn in otelglobal `SetStatus()` when grabbing the status code. ([#675](https://github.com/open-telemetry/opentelemetry-go-instrumentation/pull/675))
 - Reset `proc` offset after a failed iteration. ([#681](https://github.com/open-telemetry/opentelemetry-go-instrumentation/pull/681))
 - Avoid using runtime.NumCPU to get the number of CPUs on the system before remote mmap ([#680](https://github.com/open-telemetry/opentelemetry-go-instrumentation/pull/680))
+- Cleanup eBPF maps only when we stop using the memory ([#682](https://github.com/open-telemetry/opentelemetry-go-instrumentation/pull/682))
 
 ## [v0.10.1-alpha] - 2024-01-10
 

internal/pkg/instrumentation/bpf/go.opentelemetry.io/otel/traceglobal/bpf/probe.bpf.c

@@ -120,12 +120,11 @@ int uprobe_Start_Returns(struct pt_regs *ctx) {
     if (span_name == NULL) {
         return 0;
     }
-    bpf_map_delete_elem(&span_name_by_context, &key);
 
     u32 zero_span_key = 0;
     struct otel_span_t *zero_span = bpf_map_lookup_elem(&otel_span_storage_map, &zero_span_key);
     if (zero_span == NULL) {
-        return 0;
+        goto done;
     }
 
     u32 otel_span_key = 1;
@@ -134,7 +133,7 @@ int uprobe_Start_Returns(struct pt_regs *ctx) {
     // Get a pointer to the zeroed span
     struct otel_span_t *otel_span = bpf_map_lookup_elem(&otel_span_storage_map, &otel_span_key);
     if (otel_span == NULL) {
-        return 0;
+        goto done;
     }
 
     otel_span->start_time = bpf_ktime_get_ns();
@@ -156,6 +155,9 @@ int uprobe_Start_Returns(struct pt_regs *ctx) {
 
     bpf_map_update_elem(&active_spans_by_span_ptr, &span_ptr_val, otel_span, 0);
     start_tracking_span(ret_context_ptr_val, &otel_span->sc);
+
+done:
+    bpf_map_delete_elem(&span_name_by_context, &key);
     return 0;
 }
 
@@ -253,9 +255,10 @@ int uprobe_End(struct pt_regs *ctx) {
         return 0;
     }
     span->end_time = bpf_ktime_get_ns();
-    bpf_map_delete_elem(&active_spans_by_span_ptr, &non_recording_span_ptr);
     stop_tracking_span(&span->sc, &span->psc);
 
     bpf_perf_event_output(ctx, &events, BPF_F_CURRENT_CPU, span, sizeof(*span));
+
+    bpf_map_delete_elem(&active_spans_by_span_ptr, &non_recording_span_ptr);
     return 0;
 }

internal/pkg/instrumentation/bpf/google.golang.org/grpc/client/bpf/probe.bpf.c

@@ -140,7 +140,6 @@ int uprobe_LoopyWriter_HeaderHandler(struct pt_regs *ctx)
         return 0;
     }
 
-    bpf_map_delete_elem(&streamid_to_span_contexts, &stream_id);
     struct go_slice slice = {};
     struct go_slice_user_ptr slice_user_ptr = {};
     slice_user_ptr.array = (void *)(headerFrame_ptr + (headerFrame_hf_pos));
@@ -157,7 +156,7 @@ int uprobe_LoopyWriter_HeaderHandler(struct pt_regs *ctx)
     struct go_string key_str = write_user_go_string(tp_key, sizeof(tp_key));
     if (key_str.len == 0) {
         bpf_printk("key write failed, aborting ebpf probe");
-        return 0;
+        goto done;
     }
 
     // Write headers
@@ -166,12 +165,15 @@ int uprobe_LoopyWriter_HeaderHandler(struct pt_regs *ctx)
     struct go_string val_str = write_user_go_string(val, sizeof(val));
     if (val_str.len == 0) {
         bpf_printk("val write failed, aborting ebpf probe");
-        return 0;
+        goto done;
     }
     struct hpack_header_field hf = {};
     hf.name = key_str;
     hf.value = val_str;
     append_item_to_slice(&slice, &hf, sizeof(hf), &slice_user_ptr);
+done:
+    bpf_map_delete_elem(&streamid_to_span_contexts, &stream_id);
+
     return 0;
 }
 

internal/pkg/instrumentation/bpf/net/http/client/bpf/probe.bpf.c

@@ -236,7 +236,6 @@ int uprobe_Transport_roundTrip_Returns(struct pt_regs *ctx) {
         bpf_printk("probe_Transport_roundTrip_Returns: entry_state is NULL");
         return 0;
     }
-    bpf_map_delete_elem(&http_events, &key);
 
     if (is_register_abi()) {
         // Getting the returned response
@@ -249,5 +248,7 @@ int uprobe_Transport_roundTrip_Returns(struct pt_regs *ctx) {
 
     bpf_perf_event_output(ctx, &events, BPF_F_CURRENT_CPU, http_req_span, sizeof(*http_req_span));
     stop_tracking_span(&http_req_span->sc, &http_req_span->psc);
+
+    bpf_map_delete_elem(&http_events, &key);
     return 0;
 }