RFR: 8202634: Metaspace: simplify SpaceManager lists

[Thomas Stüfe]

(jdk-submit tests ok. SAP tests did not show anything attributable to
this patch.)

On Mon, May 7, 2018 at 5:29 PM, Thomas Stüfe <thomas.stuefe at gmail.com> 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.
>
> - Unfolded SpaceManager::initialize into Spacemanager constructor (I
> prefer initializing members in ctor init lists)
>
> - 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.
>
> Thank you,
>
> Thomas