RFR: 8058963: CollectorPolicy::satisfy_failed_metadata_allocation can avoid some safepoints

[Bengt Rutisson]

On 2014-09-26 16:45, Erik Helin wrote:
> Hi Bengt,
>
> On 2014-09-26 12:49, Bengt Rutisson wrote:
>>
>> Hi Erik,
>>
>> The change looks good.
>
> thanks!
>
> On 2014-09-26 12:49, Bengt Rutisson wrote:
>> One minor thing is that Metaspace::expand_and_allocate() and
>> Metaspace::allocate() have different exposure even though they are both
>> supposed to be internal to Metaspace. It would be nice to treat them the
>> same way. Talked to Erik and we think that keeping the friend
>> declaration of CollectorPolicy makes sense and in that case we can move
>> expand_and_allocate() from being public to being private.
>
> Good idea, I've uploaded new webrevs:
> - full: http://cr.openjdk.java.net/~ehelin/8058963/webrev.01/
> - inc: http://cr.openjdk.java.net/~ehelin/8058963/webrev.00-01/

Looks good.

Bengt



>
> Thanks,
> Erik
>
>> Thanks,
>> Bengt
>>
>>
>> On 2014-09-23 17:15, Erik Helin wrote:
>>> Hi all,
>>>
>>> this small change enables us to skip two possible safepoints in
>>> CollectorPolicy::satisfy_failed_metadata_allocation:
>>>
>>> 1. When a thread continues a loop after having been stalled due to a
>>> GC_locker initiated Full GC.
>>> 2. When the VM_CollectForMetadata VM operation's prologue fails
>>> because a full GC has already been run just prior to the
>>> CollectForMetadata VM operation.
>>>
>>> The way this is done is simply by trying to allocate at the start of
>>> the loop. This way, whenever we loop around and a full GC has
>>> happened, the allocation request might be satisfied and we can do an
>>> early return.
>>>
>>> Webrev:
>>> http://cr.openjdk.java.net/~ehelin/8058963/webrev.00/
>>>
>>> Bug:
>>> https://bugs.openjdk.java.net/browse/JDK-8058963
>>>
>>> Testing:
>>> - JPRT
>>> - Aurora:
>>>   - Kitchensink
>>>   - Weblogic+Medrec
>>>   - runThese
>>>   - vm.quick, regression, gc, compiler, runtime, parallel class 
>>> loading,
>>>     metaspace, oom
>>>   - JTReg tests
>>>
>>> Thanks,
>>> Erik
>>