Fix names in eBPF scripts

tools/tracing/timeline/README.md

@@ -19,7 +19,7 @@ Suite.
 Run the following command with a **normal** user (*not* as `root` or using `sudo`):
 
 ```shell
-./capture.py -e 47 -m /path/to/libmmtk_openjdk.so --no-root-nodes
+./capture.py -e 47 -m /path/to/libmmtk_openjdk.so --no-pinning-roots
 ```
 
 `-e 47` means we only capture one GC in every 47 GCs because otherwise it will have to print too
@@ -37,7 +37,7 @@ us an illusion of "all GCs are nursery GC" or "all GCs are full-heap GC".  This
 
 [aliasing effect]: https://en.wikipedia.org/wiki/Aliasing
 
-`--no-root-nodes` skips the `process_root_nodes` USDT which does not exist in `libmmtk_openjdk.so`.
+`--no-pinning-roots` skips the `process_pinning_roots` USDT which does not exist in `libmmtk_openjdk.so`.
 
 Replace `/path/to/libmmtk_openjdk.so` with the actual path to the `.so` that contains MMTk and its
 binding.
@@ -124,7 +124,7 @@ This means things are working properly.  Now re-run `./capture.py` again, but pi
 file.
 
 ```
-./capture.py -e 47 -m /path/to/libmmtk_openjdk.so --no-root-nodes > mybenchmark.log
+./capture.py -e 47 -m /path/to/libmmtk_openjdk.so --no-pinning-roots > mybenchmark.log
 ```
 
 Type the root password if prompted.

tools/tracing/timeline/capture.bt

@@ -18,6 +18,10 @@ END {
     system("rm $TMP_FILE");
 }
 
+// We only set up the harness_begin/harness_end probes when the -H option is set.
+// Some VM bindings don't implement harness_begin/harness_end, and those trace points don't exist.
+// The user will see error if they add the -H option.
+//////// BEGIN:HARNESS
 usdt:$MMTK:mmtk:harness_begin {
     if (@harness) {
         //begin collecting data at harness_begin (start of final iteration)
@@ -32,6 +36,7 @@ usdt:$MMTK:mmtk:harness_end {
         exit();
     }
 }
+//////// END:HARNESS
 
 usdt:$MMTK:mmtk:gc_start {
     // Close the "GC_REQUEST_WAIT" span opened at `gc_requested`, right before opening "GC".
@@ -102,13 +107,13 @@ usdt:$MMTK:mmtk:roots {
     printf("roots,meta,%d,%lu,%lu,%lu\n", tid, nsecs, arg0, arg1);
 }
 
-//////// BEGIN:PROCESS_ROOT_NODES
-usdt:$MMTK:mmtk:process_root_nodes {
+//////// BEGIN:PROCESS_PINNING_ROOTS
+usdt:$MMTK:mmtk:process_pinning_roots {
     if (@enable_print) {
-        printf("process_root_nodes,meta,%d,%lu,%lu,%lu\n", tid, nsecs, arg0, arg1);
+        printf("process_pinning_roots,meta,%d,%lu,%lu,%lu\n", tid, nsecs, arg0, arg1);
     }
 }
-//////// END:PROCESS_ROOT_NODES
+//////// END:PROCESS_PINNING_ROOTS
 
 usdt:$MMTK:mmtk:process_slots {
     if (@enable_print) {

tools/tracing/timeline/capture.py

@@ -31,8 +31,8 @@ def get_args():
                         help="Only capture every N-th GC"),
     parser.add_argument("-x", "--extra", metavar="S", type=str, action="append",
                         help="Append script S after 'capture.bt'.  Use this option multiple times to append multiple scripts."),
-    parser.add_argument("--no-root-nodes", action="store_true",
-                        help="Do not add 'process_root_nodes' probe." +
+    parser.add_argument("--no-pinning-roots", action="store_true",
+                        help="Do not add 'process_pinning_roots' probe." +
                         "  This USDT is conditionally generated by Rust generics, and may not exist in some VM bindings.")
     parser.add_argument("--enable-sweep-chunk-ms", action="store_true",
                         help="enable the 'sweep_chunk_ms' probe." +
@@ -77,12 +77,15 @@ def main():
         script_lines = script_path.read_text().splitlines()
         scripts_lines.extend(script_lines)
 
-    if args.no_root_nodes:
-        delete_lines_between(scripts_lines, "BEGIN:PROCESS_ROOT_NODES", "END:PROCESS_ROOT_NODES")
+    if args.no_pinning_roots:
+        delete_lines_between(scripts_lines, "BEGIN:PROCESS_PINNING_ROOTS", "END:PROCESS_PINNING_ROOTS")
 
     if not args.enable_sweep_chunk_ms:
         delete_lines_between(scripts_lines, "BEGIN:SWEEP_CHUNK_MS", "END:SWEEP_CHUNK_MS")
 
+    if not args.harness:
+        delete_lines_between(scripts_lines, "BEGIN:HARNESS", "END:HARNESS")
+
     merged_script = "\n".join(scripts_lines)
 
     template = Template(merged_script)

tools/tracing/timeline/visualize.py

@@ -249,7 +249,7 @@ def enrich_meta(self, name, tid, ts, gc, wp, args):
         # bpftrace may drop events.  Be conservative.
         if wp is not None:
             match name:
-                case "process_root_nodes":
+                case "process_pinning_roots":
                     wp["args"] |= {
                         "num_roots": int(args[0]),
                         "num_enqueued_nodes": int(args[1]),