jvm load too many classes

[Rémi Forax]

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
> 303
>
> $ grep Loaded hw.verbose.jdk6u21 | wc -l
> 323
>
> $ grep Loaded hw.verbose.jdk7 | wc -l
> 329

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.

Rémi

>
>
>> 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 <mandy.chung at oracle.com>:
>>> 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
>>>
>>>
>

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