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

[Stefan Karlsson]

Hi Coleen,

On 2014-05-13 02:19, 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 fixing this.

I looked at the version at:
http://cr.openjdk.java.net/~coleenp/8038212_3

Could you explain why you added the storestore here? Shouldn't it be 
placed after the node has been initialized but before it is linked into 
the list?

*** 1219,1228 ****
--- 1237,1248 ----
     if (virtual_space_list() == NULL) {
         set_virtual_space_list(new_entry);
     } else {
       current_virtual_space()->set_next(new_entry);
     }
+   // ensure lock-free iteration sees fully initialized node
+   OrderAccess::storestore();
     set_current_virtual_space(new_entry);
     inc_reserved_words(new_entry->reserved_words());
     inc_committed_words(new_entry->committed_words());
     inc_virtual_space_count();
   #ifdef ASSERT


Otherwise, this looks good.

thanks,
StefanK
>
> Marcus L. tested it with nashorn tests.
>
> Thanks,
> Coleen