JDK-8212220 increased the default timeout to 300 seconds/5 minutes
in order to get back to the total timeout value of 20 minutes when the
default timeout factor 4 is in use. The frequency has been reduced back
to being rare (like when the default timeout factor was 10).

Since 2018.10.24, we have seen a total of 3 failures in the jdk/jdk CI
testing: 10.31, 11.06, and 11.09. The longest of those timeouts was
24 minutes 28 seconds.

$ hg diff
diff -r b915bd68d907 test/hotspot/jtreg/vmTestbase/metaspace/stressDictionary/StressDictionary.java
--- a/test/hotspot/jtreg/vmTestbase/metaspace/stressDictionary/StressDictionary.java Fri Nov 09 13:28:16 2018 -0500
+++ b/test/hotspot/jtreg/vmTestbase/metaspace/stressDictionary/StressDictionary.java Fri Nov 09 14:48:27 2018 -0500
@@ -29,7 +29,7 @@
  *
  * @library /vmTestbase /test/lib
  * @run driver jdk.test.lib.FileInstaller . .
- * @run main/othervm/timeout=300 metaspace.stressDictionary.StressDictionary -stressTime 30
+ * @run main/othervm/timeout=420 metaspace.stressDictionary.StressDictionary -stressTime 30
  */
 
 package metaspace.stressDictionary;


With a default timeout of 420 seconds and a default timeout factor
of 4, we'll have a total timeout value of 28 minutes.