Process.warmup: precompute strings coderange

This both save time for when it will be eventually needed,
and avoid mutating heap pages after a potential fork.

Instrumenting some large Rails app, I've witnessed up to
58% of String instances having their coderange still unknown.

1 files changed, 5 insertions, 0 deletions

diff --git a/gc.c b/gc.c
index 3c9adf3b00..ca018b7ae1 100644
--- a/gc.c
+++ b/gc.c
@@ -9596,6 +9596,11 @@ gc_set_candidate_object_i(void *vstart, void *vend, size_t stride, void *data)
           case T_NONE:
           case T_ZOMBIE:
             break;
+          case T_STRING:
+            // precompute the string coderange. This both save time for when it will be
+            // eventually needed, and avoid mutating heap pages after a potential fork.
+            rb_enc_str_coderange(v);
+            // fall through
           default:
             if (!RVALUE_OLD_P(v) && !RVALUE_WB_UNPROTECTED(v)) {
                 RVALUE_AGE_SET_CANDIDATE(objspace, v);