> ### Motivation and proposal
> Hi, heap dump brings about pauses for application's execution(STW), this is a 
> well-known pain. JDK-8252842 have added parallel support to heapdump in an 
> attempt to alleviate this issue. However, all concurrent threads 
> competitively write heap data to the same file, and more memory is required 
> to maintain the concurrent buffer queue. In experiments, we did not feel a 
> significant performance improvement from that.
> 
> The minor-pause solution, which is presented in this PR, is a two-stage 
> segmented heap dump:
> 
> 1. Stage One(STW): Concurrent threads directly write data to multiple heap 
> files.
> 2. Stage Two(Non-STW): Merge multiple heap files into one complete heap dump 
> file.
> 
> Now concurrent worker threads are not required to maintain a buffer queue, 
> which would result in more memory overhead, nor do they need to compete for 
> locks. The changes in the overall design are as follows:
> 
> ![image](https://github.com/openjdk/jdk/assets/5010047/86d2717d-c621-446f-98c2-cce761ec8db5)
> <p align="center">Fig1. Before</p>
> 
> ![image](https://github.com/openjdk/jdk/assets/5010047/c912c516-83b6-4343-a2e8-5d5bdb99cb87)
> <p align="center">Fig1. After this patch</p>
> 
> ### Performance evaluation
> | memory | numOfThread | STW         | Total      | Compression |
> | --- | --------- | -------------- | ------------ | -------- |
> | 8g | 1 thread | 15.612 secs | 15.612 secs | N |
> | 8g | 32 thread |  2.5617250 secs | 14.498 secs | N |
> | 8g | 32 thread | 2.3084878 secs | 3.198 secs | Compress1 |
> | 8g | 32 thread | 10.9355128 secs | 21.882 secs | Compress2 |
> | 8g | 96 thread | 2.6790452 secs | 14.012 secs | N |
> | 8g | 96 thread | 2.3044796 secs | 3.589 secs | Compress1 |
> | 8g | 96 thread | 9.7585151 secs | 20.219 secs| Compress2 |
> | 16g | 1 thread | 26.278 secs | 26.278 secs | N |
> | 16g | 32 thread |  5.2313740 secs | 26.417 secs | N |
> | 16g | 32 thread | 5.6946983 secs | 6.538 secs | Compress1 |
> | 16g | 32 thread | 21.8211105 secs | 41.133 secs | Compress2 |
> | 16g | 96 thread | 6.2445556 secs | 27.141 secs | N |
> | 16g | 96 thread | 4.6007096 secs | 6.259 secs | Compress1 |
> | 16g | 96 thread | 19.2965783 secs |  39.007 secs | Compress2 |
> | 32g | 1 thread | 48.149 secs | 48.149 secs | N |
> | 32g | 32 thread | 10.7734677 secs | 61.643 secs | N |
> | 32g | 32 thread | 10.1642097 secs | 10.903 secs | Compress1 |
> | 32g | 32 thread | 43.8407607 secs | 88.152 secs | Compress2 |
> | 32g | 96 thread | 13.1522042 secs | 61.432 secs | N |
> | 32g | 96 thread | 9.0954641 secs | 9.885 secs | C...

Yi Yang has updated the pull request incrementally with one additional commit 
since the last revision:

  memory leak

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/13667/files
  - new: https://git.openjdk.org/jdk/pull/13667/files/ecab3116..2012b5ca

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=13667&range=13
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=13667&range=12-13

  Stats: 52 lines in 1 file changed: 22 ins; 13 del; 17 mod
  Patch: https://git.openjdk.org/jdk/pull/13667.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13667/head:pull/13667

PR: https://git.openjdk.org/jdk/pull/13667

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