diff --git a/read-cache.c b/read-cache.c
index 47915e4bc2800f..2bf3c98d5532fe 100644
--- a/read-cache.c
+++ b/read-cache.c
@@ -1701,7 +1701,10 @@ static int read_index_extension(struct index_state *istate,
 {
 	switch (CACHE_EXT(ext)) {
 	case CACHE_EXT_TREE:
+		trace2_region_enter("index", "read/extension/cache_tree", NULL);
 		istate->cache_tree = cache_tree_read(data, sz);
+		trace2_data_intmax("index", NULL, "read/extension/cache_tree/bytes", (intmax_t)sz);
+		trace2_region_leave("index", "read/extension/cache_tree", NULL);
 		break;
 	case CACHE_EXT_RESOLVE_UNDO:
 		istate->resolve_undo = resolve_undo_read(data, sz);
@@ -1957,6 +1960,17 @@ static void *load_index_extensions(void *_data)
 	return NULL;
 }
 
+static void *load_index_extensions_threadproc(void *_data)
+{
+	void *result;
+
+	trace2_thread_start("load_index_extensions");
+	result = load_index_extensions(_data);
+	trace2_thread_exit();
+
+	return result;
+}
+
 /*
  * A helper function that will load the specified range of cache entries
  * from the memory mapped file and add them to the given index.
@@ -2032,12 +2046,17 @@ static void *load_cache_entries_thread(void *_data)
 	struct load_cache_entries_thread_data *p = _data;
 	int i;
 
+	trace2_thread_start("load_cache_entries");
+
 	/* iterate across all ieot blocks assigned to this thread */
 	for (i = p->ieot_start; i < p->ieot_start + p->ieot_blocks; i++) {
 		p->consumed += load_cache_entry_block(p->istate, p->ce_mem_pool,
 			p->offset, p->ieot->entries[i].nr, p->mmap, p->ieot->entries[i].offset, NULL);
 		p->offset += p->ieot->entries[i].nr;
 	}
+
+	trace2_thread_exit();
+
 	return NULL;
 }
 
@@ -2187,7 +2206,7 @@ int do_read_index(struct index_state *istate, const char *path, int must_exist)
 			int err;
 
 			p.src_offset = extension_offset;
-			err = pthread_create(&p.pthread, NULL, load_index_extensions, &p);
+			err = pthread_create(&p.pthread, NULL, load_index_extensions_threadproc, &p);
 			if (err)
 				die(_("unable to create load_index_extensions thread: %s"), strerror(err));
 
@@ -2935,9 +2954,13 @@ static int do_write_index(struct index_state *istate, struct tempfile *tempfile,
 	if (!strip_extensions && !drop_cache_tree && istate->cache_tree) {
 		struct strbuf sb = STRBUF_INIT;
 
+		trace2_region_enter("index", "write/extension/cache_tree", NULL);
 		cache_tree_write(&sb, istate->cache_tree);
 		err = write_index_ext_header(&c, &eoie_c, newfd, CACHE_EXT_TREE, sb.len) < 0
 			|| ce_write(&c, newfd, sb.buf, sb.len) < 0;
+		trace2_data_intmax("index", NULL, "write/extension/cache_tree/bytes", (intmax_t)sb.len);
+		trace2_region_leave("index", "write/extension/cache_tree", NULL);
+
 		strbuf_release(&sb);
 		if (err)
 			return -1;