I noticed recently that the JDK8 JVM was very slow starting on systems where
the JRE is on a high-latency, remote file system. I tracked this down to the
reading of tzdb.dat. In java/time/zone/TzdbZoneRulesProvider.java and
sun/util/calendar/ZoneInfoFile.java the tzdb.dat file is read using a
DataInputStream directly over a FileInputStream. Consequently there ends up
being a large number of very small (often a single byte) read requests to the
underlying O/S file system. This can be fixed trivially by adding a
BufferedInputStream between the DataInputStream and the FileInputStream.
Thus this:
try (DataInputStream dis = new DataInputStream(
new FileInputStream(new File(libDir, "tzdb.dat")))) {
becomes:
try (DataInputStream dis = new DataInputStream(
new BufferedInputStream(
new FileInputStream(new File(libDir, "tzdb.dat")), 32000))) {
Tom Salter | Software Engineer | Java & Middleware Development
Unisys | 2476 Swedesford Road | Malvern, PA 19355 | 610-648-2568 |
N385-2568
