Osvaldo Doederlein wrote:
I wonder if these numbers have some variation per platform?
Yes, there are some platform-dependent classes and so some loaded
classes are different on different platform.
For me (on
Windows; 32-bit JDKs), the results of this test (java -verbose:class |
grep Loaded | wc -l) are:
1.5.0_22: 239
1.6.0_21: 274
1.7.0-ea-b103: 403
I ran the helloworld. The number of loaded classes running different jdk
versions are fairly close. What test case did you use?
$ grep Loaded hw.verbose.jdk5u22 | wc -l
303
$ grep Loaded hw.verbose.jdk6u21 | wc -l
323
$ grep Loaded hw.verbose.jdk7 | wc -l
329
The diff from 1.5 to 1.6 is not bad, but JDK7 seems right now to be a
heavy regression... FWIW for such a simple test. For one thing, these
core-boot classes all come off the CDS file so their classloading
effort is relatively very small, and the delta will certainly be much
smaller for even the smallest real-world app.
Right. -verbose:class prints out all loaded classes regardless of
coming from CDS archive or not. The number of loaded classes is one
metric to the startup while class loading time + clinit time are
other important metrics. So these loaded classes has small impact
to the startup time especially with CDS is enabled.
Mandy
A+
Osvaldo
2010/7/30 Mandy Chung <[email protected]>:
Yongqiang Yang wrote:
hi,
I just type command "java" under openjdk1.6, then the jvm will load
308 classes, including java/launcher/LauncherHelp,
java/util/ResourceBundle,
java/util/Currency,
java/util/Locale,
java/net/URL
When I use jdk1.5, the jvm just load about 180 classes, not
including the classes above.
Could someone figure out something wrong?
New features and bug fixes in a new release could lead to more classes get
loaded at startup. We have done some work to lazily load classes if
appropriate (see CR 6798873: Reduce the number of classes loaded and class
dependencies).
Mandy
