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

[Mandy Chung]

On 10/27/2014 9:38 PM, Ioi Lam wrote:
>
>> 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.

No, set it in the command-line (i.e. @run) is fine.

Removing line 44-58  should do it.

>> 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
>         = 
> "true".equals(VM.getSavedProperty("sun.cds.enableSharedLookupCache"));
>
> 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.
>             disableAllLookupCaches();
>         }
>     }
>
> their lookupCacheURLs[] fields will all be set to null. As a result, 
> getLookupCacheForClassLoader and knownToNotExist0 will never be called.
>

It will call getLookupCacheURLs.  It's just a sanity test and it's fine 
to call one but not all three.

> 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?

As long as A.test and B.test are invoked and finishes, it should be 
adequate.

Mandy