RFR (M) 8061651 - Interface to the Lookup Index Cache to improve URLClassPath search time

Jiangli Zhou jiangli.zhou at oracle.com
Tue Oct 21 21:04:43 UTC 2014

Hi Ioi,

Here are some comments from me:

In ClassLoader::setup_search_path, if canonicalize is true it's not 
necessary to allocate the 'path' and copy the 'class_path' to 'path'.

In free_array, is it possible to disable it only when PrintSharedSpaces 
is enabled, instead of disabling it for all?

Is verifying class name needed in 
Java_sun_misc_URLClassPath_knownToNotExist0? The class name will be 
verified when the class loader loads the class.

CanlookupCacheEnabled flag change during runtime? In getLookupCache() 
the flag is checked more than once.


On 10/21/2014 10:27 AM, Ioi Lam wrote:
> Please review this fix:
> http://cr.openjdk.java.net/~iklam/8061651-lookup-index-open-v1/
> Bug: Add an interface to the JVM's Class/Resource Lookup Index Cache 
> for improving sun.misc.URLClassPath search time
>     https://bugs.openjdk.java.net/browse/JDK-8061651
> Summary of fix:
>     Some J2EE environments have lots of JAR files in the
>     classpath. However, during run-time, most classes are loaded by
>     custom classloaders which delegate to the system loader. As a
>     result, each class loaded by a custom classloader will cause many
>     JAR search failures (in sun.misc.URLClassPath).
>     To limit the number of searches in URLClassPath, the 8uX HotSpot
>     VM is going to include a Class/Resource Lookup Index Cache that
>     records information about the class/resource entries in the JAR
>     files in the classpath. This can be used to improve
>     sun.misc.URLClassPath search time.
>     This is part 1 of the REF -- we are adding appropriate interfaces
>     in both the JDK code and the HotSpot code to access this cache.
>     URLClassPath.java is modified to use JNI to call into the HotSpot
>     JVM_XXX APIs to access the cache.
>     The implementation of this cache is done in part 2 of this RFE.
>     Note that this enhancement is for JDK 8uX only. In JDK9 and
>     beyond, we are considering an alternative implementation where the
>     cache is maintained in the core libs code, outside of HotSpot.
> Tests:
>     JPRT
>     Adhoc SQE tests
> Thanks
> - Ioi

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