Request for review: 6976350 G1: deal with fragmentation while copying objects during GC

[Tao Mao]

Thank you for looking at it, Jon.

Tao

On 5/29/13 7:45 PM, Jon Masamitsu wrote:
> Tao,
>
> These latest changes look good.
>
> Jon
>
> On 5/20/2013 5:11 PM, Tao Mao wrote:
>> Hi all,
>>
>> a new webrev
>> http://cr.openjdk.java.net/~tamao/6976350/webrev.04/
>>
>> diff:
>> (1) John Cuthbertson and I figured out the way to handle "retire an 
>> old buffer, allocate and set a new one" and it can possibly make the 
>> usage of allocation buffer a little more efficient.
>> (2) Make the assertion as John suggested and provide some harness 
>> (i.e. making retire() a virtual function) to cope with it.
>>
>> Thanks.
>> Tao
>>
>> On 5/15/13 10:58 PM, John Cuthbertson wrote:
>>> Hi Tao,
>>>
>>> This looks excellent. One minor question: does it make sense to 
>>> assert that each buffer has been retired? It might save a missed 
>>> call to PSS::retire_alloc_buffers. I'll leave the decision to you. 
>>> Ship it.
>>>
>>> JohnC
>>>
>>>
>>> On 5/14/2013 3:06 PM, Tao Mao wrote:
>>>> To the open list:
>>>>
>>>> new webrev:
>>>> http://cr.openjdk.java.net/~tamao/6976350/webrev.03/
>>>>
>>>> I took suggestion from many reviewers into consideration and came 
>>>> up with the current cleaner solution.
>>>>
>>>> Thank you.
>>>> Tao
>>>>
>>>>
>>>> On 5/14/13 2:26 PM, Jon Masamitsu wrote:
>>>>> What's the status of this review?
>>>>>
>>>>> The last mail I  could find in my mail boxes was a comment
>>>>> from Thomas.
>>>>>
>>>>> Jon
>>>>>
>>>>> On 1/28/13 12:21 PM, Tao Mao wrote:
>>>>>> 6976350 G1: deal with fragmentation while copying objects during GC
>>>>>> https://jbs.oracle.com/bugs/browse/JDK-6976350
>>>>>>
>>>>>> webrev:
>>>>>> http://cr.openjdk.java.net/~tamao/6976350/webrev.00/
>>>>>>
>>>>>> changeset:
>>>>>> Basically, we want to reuse more of par-allocation buffers 
>>>>>> instead of retiring it immediately when it encounters an object 
>>>>>> larger than its remaining part.
>>>>>>
>>>>>> (1) instead of previously using one allocation buffer per GC 
>>>>>> purpose, we use N(=2) buffers per GC purpose and modify the 
>>>>>> corresponding code. The changeset would easily scale up to 
>>>>>> whatever N (though Tony Printezis suggests 2, or 3 may be good 
>>>>>> enough)
>>>>>>
>>>>>> *(2) Two places of cleanup: allocate_during_gc_slow() is removed 
>>>>>> due to its never being called.
>>>>>>                                               access modifier 
>>>>>> (public) before trim_queue() is redundant.
>>>>>>
>>>>>>
>>>>>
>>>
>