RFR 8038212: Method::is_valid_method() check has performance regression impact for stackwalking

[Coleen Phillimore]

Hi Mikael,

On 5/13/14, 6:33 AM, Mikael Gerdin wrote:
> Hi Coleen,
>
> On Monday 12 May 2014 20.19.15 Coleen Phillimore wrote:
>> Summary: Only prune metaspace virtual spaces at safepoint so walking
>> them is safe outside a safepoint.
>>
>> Walking class loader data graph for contains is really slow for
>> applications like nashorn that has a lot of class loader data.
>>
>> Tested with nsk.quick.testlist, jtreg tests, and jck tests.  Also ran
>>
>> open webrev at http://cr.openjdk.java.net/~coleenp/8038212/
>> bug link https://bugs.openjdk.java.net/browse/JDK-8038212
> Thanks for taking care of this fix.
> I think the idea of deferring CLDG::purge to the next safepoint cleanup is
> sound.

Oh great!  I'm glad you agree.
>
> I like the removal of CLDG::contains since it makes more sense to ask
> Metaspace straight up.
>
> I have a small question about the test you added:
>
> 3798   static void test_contains() {
> 3799     // Test that all the methods in the CLDG are contained
> 3800     ClassLoaderDataGraph::methods_do(assert_contains);
> 3801   }
>
> Have we always allocated methods at this point in the VM startup?

I thought this ExecuteVMInternalTests (or whatever the option is called) 
is at shutdown?  I'll check.
> Should we also test CLDG::classes_do to make sure it works for the compressed
> class space?

I had that same thought this morning.  Yes, I'll add it.

Coleen

>
> /Mikael
>
>> Marcus L. tested it with nashorn tests.
>>
>> Thanks,
>> Coleen