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, 12 insertions, 0 deletions

diff --git a/test/ruby/test_process.rb b/test/ruby/test_process.rb
index 6ca16733bb..9846f5e2db 100644
--- a/test/ruby/test_process.rb
+++ b/test/ruby/test_process.rb
@@ -2709,4 +2709,16 @@ EOS
       assert_equal compact_count + 1, GC.stat(:compact_count)
     end;
   end
+
+  def test_warmup_precompute_string_coderange
+    assert_separately([], "#{<<~"begin;"}\n#{<<~'end;'}")
+    require 'objspace'
+    begin;
+      obj = "a" * 12
+      obj.force_encoding(Encoding::BINARY)
+      assert_include(ObjectSpace.dump(obj), '"coderange":"unknown"')
+      Process.warmup
+      assert_include(ObjectSpace.dump(obj), '"coderange":"7bit"')
+    end;
+  end
 end