RFR (M) 8061651 - Interface to the Lookup Index Cache to improve URLClassPath search time (round 3)

Ioi Lam ioi.lam at oracle.com
Tue Oct 28 04:38:34 UTC 2014

On 10/27/14, 7:04 PM, Mandy Chung wrote:
> On 10/27/2014 3:32 PM, Ioi Lam wrote:
>> Hi David, I have update the latest webrev at:
>> http://cr.openjdk.java.net/~iklam/8061651-lookup-index-open-v3/
> The update looks good.  Thanks.
>> This version also contains the JDK test case that Mandy requested:
>> http://cr.openjdk.java.net/~iklam/8061651-lookup-index-open-v3/jdk/test/sun/misc/URLClassPath/EnableLookupCache.java.html 
> What I request to add is a test setting the system property 
> (-Dsun.cds.enableSharedLookupCache=true) and continue to load class A 
> and B.  Removing line 44-58 should do it and also no need to set 
> -Dfoo.foo.bar.
Do you mean change the test to call 
System.setProperty("sun.cds.enableSharedLookupCache", "true")?

But we know that the property is checked only once, before any app 
classes are loaded. So calling System.setProperty in an application 
class won't test anything.
> It'd be good if you run this test and turn on the debug traces to make 
> sure that the application class loader and ext class loader will start 
> up with the lookup cache enabled and make up call to the VM.  As it 
> doesn't have the app cds archive, it will invalidate the cache right 
> away and continue the class lookup with null cache array.
In the latest code, if CDS is not available, lookupCacheEnabled will be 
set to false inside the static initializer of URLClassPath:

     private static volatile boolean lookupCacheEnabled

later, when the boot/ext/app loaders call into here:

     synchronized void initLookupCache(ClassLoader loader) {
         if ((lookupCacheURLs = getLookupCacheURLs(loader)) != null) {
             lookupCacheLoader = loader;
         } else {
             // This JVM instance does not support lookup cache.

their lookupCacheURLs[] fields will all be set to null. As a result, 
getLookupCacheForClassLoader and knownToNotExist0 will never be called.

I can add a DEBUG_LOOKUP_CACHE trace inside disableAllLookupCaches to 
print "lookup cache disabled", and check for that in the test. Is this OK?

- Ioi

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