RFR: 7133138 Improve io performance around timezone lookups

Seán Coffey sean.coffey at oracle.com
Tue Feb 21 18:19:38 UTC 2012

I've worked with Masayoshi on this issue. Hoping to push to JDK8 and 
backport to 7u and a jdk6 once baked for a while.

Some windows boxes were showing performance issues when attempting to 
iterate through all available timezones available in the JRE. Changes 
made here should reduce the amount of file stat calls made on 
jre/lib/zi/* files.  Tweaks are made to the alias table also to reduce 
number of aliases that require lookup.

All TZ regression tests run without issue. I've seen a 20-30% speed up 
on iteration of timezones on windows as a result. Unix doesn't appear to 
suffer as badly from such a file IO hit.



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