[9] RFR (XS): 8151623: Zap freed Metaspace chunks in non-product binaries

[Dean Long]

On 3/10/2016 1:15 PM, Vladimir Ivanov wrote:
> Thanks, Dean.
>
> Updated version:
>   http://cr.openjdk.java.net/~vlivanov/8151623/webrev.01
>

Still good.

> On 3/10/16 10:43 PM, Dean Long wrote:
>> This looks good.  I was experimenting with a similar change.  The
>> comment nearby saying
>> "Do not mangle freed Metachunks" made me wonder if it was safe. Could
>> you update the
> Good catch, fixed. Unless there's something useful stored after the 
> header in a free chunk, it should be safe.
>
>> comment if this is indeed safe?  Also, is there a Zap<something> flag we
>> can use to turn
>> this off and on?
> Do you suggest a non-product or a diagnostic flag (to be able to turn 
> it on in product binaries)?
>

I thought there was a Zap flag for metadata, but maybe not.  I don't 
know if it's worth the trouble to add a new flag.

dl

> Best regards,
> Vladimir Ivanov
>
>> On 3/10/2016 10:55 AM, Vladimir Ivanov wrote:
>>> http://cr.openjdk.java.net/~vlivanov/8151623/webrev.00
>>> https://bugs.openjdk.java.net/browse/JDK-8151623
>>>
>>> Zap freed Metaspace chunks in non-product binaries to catch stray
>>> accesses to unloaded classes.
>>>
>>> Testing: JPRT, RBT (in progress): hotspot/test:hotspot_all,
>>> jdk/test:tier1 & tier2, vm.parallel_class_loading.testlist,
>>> vm.gc.testlist, BigApps w/ fastdebug binaries.
>>>
>>> Thanks!
>>>
>>> Best regards,
>>> Vladimir Ivanov
>>