jvm load too many classes
forax at univ-mlv.fr
Sat Jul 31 20:31:39 UTC 2010
Le 30/07/2010 21:59, Mandy Chung a écrit :
> 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
> $ grep Loaded hw.verbose.jdk6u21 | wc -l
> $ grep Loaded hw.verbose.jdk7 | wc -l
There is a big diff (at least on linux) if you just try to print the
help of the VM,
i.e pass no argument.
jdk1.6.0_21: 274 classes
jdk1.7.0b103: 364 classes
I join the diff.
Some classes of java.text.*, java.util.ResourceBundle* and
some classes related to locale and currency are loaded eagerly.
>> 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.
>> 2010/7/30 Mandy Chung <mandy.chung at oracle.com>:
>>> Yongqiang Yang wrote:
>>>> I just type command "java" under openjdk1.6, then the jvm will
>>>> 308 classes, including java/launcher/LauncherHelp,
>>>> 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
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