Environment Information

• JRuby version: 9.2.20.1 (including latest 9.2.21.0-SNAPSHOT)
• Operating system: Windows 10

Expected Behavior

• Startup of jQAssistant/AsciidoctorJ which makes use of JRuby should be a matter of milliseconds or at most seconds

Actual Behavior

• The issue which had been fixed in JarCache checking for File.lastModified heavily slowing down startup #6730 re-appeared in virtualized, highly secured corporate Windows environments of a customer, startup again takes 5-8 minutes

Possible Solution

• The solution in JarCache checking for File.lastModified heavily slowing down startup #6730 was to reduce the amount of expensive File.lastModified calls in JarCache by introducing a grace-period of 500ms between checks (see https://github.com/jruby/jruby/blob/jruby-9.2/core/src/main/java/org/jruby/util/JarCache.java#L45). I verified that increasing the value to 750ms or 1s solves the issue again and I can provide an according PR. The question is if this value should be made configurable.