RFR: 8202634: Metaspace: simplify SpaceManager lists

[Thomas Stüfe]

Hi Coleen,

thanks for the review!

..Thomas

On Tue, May 8, 2018 at 5:53 PM,  <coleen.phillimore at oracle.com> wrote:
>
> This change looks great.  Reviewed.
>
> On 5/7/18 11:29 AM, Thomas Stüfe wrote:
>>
>> Hi all,
>>
>> may I please have reviews for this small simplification.
>>
>> Bug: https://bugs.openjdk.java.net/browse/JDK-8202634
>> webrev:
>> http://cr.openjdk.java.net/~stuefe/webrevs/8202634-simplify-spacemanager/webrev.00/webrev/
>>
>> This replaces the four separate in-use-chunk-lists in SpaceManager
>> with a single one. The reasoning behind this is that we do not need to
>> keep the chunks sorted by chunk size, a single list containing all
>> chunks of all sizes in use by this SpaceManager is enough, and it
>> simplifies the coding.
>>
>> There is only one place where we really did use the former
>> by-chunktype lists - that is to count how many chunks per chunk type
>> there are.
>>
>> However, arguably that is better done with running counters, so this
>> is what I did. The added benefit is that in
>> SpaceManager::calc_chunk_size() we do not need to walk the lists
>> anymore to sum up chunks.
>>
>> Changes in detail:
>>
>> - removed the "ChunkIndex" argument in
>> ChunkManager::return_single_chunk() and
>> Chunkmanager::return_chunk_list() - that argument was unnecessary,
>> since the Metachunk we return knows its index.
>
>
> good.
>>
>>
>> - Unfolded SpaceManager::initialize into Spacemanager constructor (I
>> prefer initializing members in ctor init lists)
>
>
> I agree!
>>
>>
>> - replaces SpaceManager::sum_count_chunks_in_use() with running counters.
>>
>> - I dumbed down the logging inside ChunkManager::return_chunk_list()
>> somewhat. Should anyone miss the former details, I can reinstate it.
>
>
> I don't think we'll miss the implementation details in the logging. Knowing
> how much space is returned seems most useful.
>
> thanks,
> Coleen
>>
>>
>> Thank you,
>>
>> Thomas
>
>