RFR (L): 8149374: Replace C1-specific collection classes with universal collection classes

[Mikael Gerdin]

Hi Filipp

On 2016-04-01 16:27, Filipp Zhinkin wrote:
> Hi Mikael,
>
> On Thu, Mar 31, 2016 at 7:25 PM, Mikael Gerdin <mikael.gerdin at oracle.com> wrote:
>> Hi,
>>
>> I like the cleanup, can't we also remove CHeapArray in arrays.hpp?
>
> Sure! I've missed that it is not used at all.

Great!

>
>>
>> As for the CMS change, I would prefer this instead (untested!):
>> http://cr.openjdk.java.net/~mgerdin/pss-array/webrev/
>
> Thanks, your implementation looks much better.
> If you don't mind I'll incorporate it into my change.

Go ahead, that was my intention.

>
> Also, it seems like in ParNewGeneration::collect we have to create
> ResourceMark before ParScanThreadStateSet, right?

There is a ResourceMark in the caller so I don't think it's needed.
The old version of the code used resource allocation as well and was 
fine so I don't think there is a need to introduce another ResourceMark.


/Mikael

>
> Thanks,
> Filipp.
>
>>
>> /Mikael
>>
>>
>> On 2016-03-31 17:14, Vladimir Kozlov wrote:
>>>
>>> Hi Filipp,
>>>
>>> Yes, this looks better. CCing to hotspot-dev for Runtime and GC groups
>>> to look on.
>>>
>>> Thanks,
>>> Vladimir
>>>
>>> On 3/31/16 8:08 AM, Filipp Zhinkin wrote:
>>>>
>>>> Hi Vladimir,
>>>>
>>>> thank you for looking at this change.
>>>>
>>>> On Wed, Mar 30, 2016 at 1:18 AM, Vladimir Kozlov
>>>> <vladimir.kozlov at oracle.com> wrote:
>>>>>
>>>>> Nice clean up but I don't see any source code removed. What benefits
>>>>> we have
>>>>> then?
>>>>> I understand that we don't generate subclasses for ResourceArray and use
>>>>> GrowableArray. But it will not save space I think.
>>>>> What prevents us to remove ResourceArray at all?
>>>>
>>>>
>>>> CMS's ParScanThreadStateSet is inherited from ResourceArray,
>>>> so it should be updated before removing ResourceArray:
>>>>
>>>> http://cr.openjdk.java.net/~fzhinkin/8149374/webrev.01/
>>>>
>>>>>
>>>>> On 3/11/16 3:42 AM, Filipp Zhinkin wrote:
>>>>>>
>>>>>>
>>>>>> Hi all,
>>>>>>
>>>>>> please review a fix for JDK-8149374:
>>>>>>
>>>>>> Webrev: http://cr.openjdk.java.net/~fzhinkin/8149374/webrev.00/
>>>>>> Bug: https://bugs.openjdk.java.net/browse/JDK-8149374
>>>>>> Testing done: hotspot_all tests + CTW
>>>>>>
>>>>>> I've replaced all usages of collections defined via define_array and
>>>>>> define_stack macros with GrowableArray.
>>>>>>
>>>>>> There are good and bad news regarding performance impact of that
>>>>>> change.
>>>>>> Unfortunately, C1 compilation time for CTW-scenario w/ release bits
>>>>>> increased from 51.07±0.28s to 52.99±0.23s (it's about 3.5%).
>>>>>
>>>>>
>>>>>
>>>>> It is acceptable regression I think. I don't think we should optimize
>>>>> and
>>>>> make more complex GrowableArray just to save 0.5% of performance for C2.
>>>>
>>>>
>>>> As long as GrowableArray is used in different Hotspot's subsystems it
>>>> may be beneficial to optimize it,
>>>> but I've executed SPECjvm2008's startup.* benchmarks and there were no
>>>> significant difference.
>>>>
>>>> If ~3% regression is OK for C1 then I'm fine with leaving
>>>> GrowableArray's initialization
>>>> in its current state unless there will be other reasons to speed it up.
>>>>
>>>> Thanks,
>>>> Filipp.
>>>>
>>>>>
>>>>> Thanks,
>>>>> Vladimir
>>>>>
>>>>>
>>>>>>
>>>>>> Such difference caused by eager initialization of GrowableArray's
>>>>>> backing array elements [1]. I can imagine when we actually need to
>>>>>> force
>>>>>> initialization and de-initialization during array's
>>>>>> growing/destruction, but for some types like c++ primitive types or
>>>>>> pointers such initialization does not make much sense, because
>>>>>> GrowableArray is not allowing to access an element which was not
>>>>>> explicitly placed inside of it. And as long as GrowableArray most
>>>>>> widely used to store pointers we're simply wasting the time with
>>>>>> initialization.
>>>>>>
>>>>>> I've measured CTW time with following workaround which implements
>>>>>> initialization for numeric types and pointers as no-op and C1
>>>>>> compilation time returned back to values that were measured before
>>>>>> original change (51.06±0.24s):
>>>>>>
>>>>>>
>>>>>> http://cr.openjdk.java.net/~fzhinkin/growableArrayInitialization/webrev/
>>>>>>
>>>>>>
>>>>>> I've also measured C2 compilation time and it dropped down by a few
>>>>>> seconds too: 1138±9s w/o GrowableArray's change and 1132±5s w/ it.
>>>>>>
>>>>>> Summing up: I guess we should avoid GrowableArray's backing array
>>>>>> initialization for some types, don't we?
>>>>>>
>>>>>> Best regards,
>>>>>> Filipp
>>>>>>
>>>>>> [1]
>>>>>>
>>>>>> http://hg.openjdk.java.net/jdk9/hs-comp/hotspot/file/323b8370b0f6/src/share/vm/utilities/growableArray.hpp#l165
>>>>>>
>>>>>>
>>>>>
>>