Integrated: JDK-8306441: Two phase segmented heap dump

[Yi Yang]

On Wed, 26 Apr 2023 09:37:46 GMT, Yi Yang <yyang at openjdk.org> wrote:

> ### 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-phase segmented heap dump:
> 
> - Phase 1(STW): Concurrent threads directly write data to multiple heap files.
> - Phase 2(Non-STW): Merge multiple heap files into one complete heap dump file. This process can happen outside safepoint.
> 
> 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/5010047/77e4764a-62b5-4336-8b45-fc880ba14c4a)
> <p align="center">Fig1. Before</p>
> 
> ![image](https://github.com/openjdk/jdk/assets/5010047/931ab874-64d1-4337-ae32-3066eed809fc)
> <p align="center">Fig2. After this patch</p>
> 
> ### Performance evaluation
> | memory | numOfThread | CompressionMode | STW | Total |
> | -------| ----------- | --------------- | --- | ---- |
> | 8g | 1 T | N | 15.612 | 15.612 |
> | 8g | 32 T | N | 2.561725 | 14.498 |
> | 8g | 32 T | C1 | 2.3084878 | 14.198 |
> | 8g | 32 T | C2 | 10.9355128 | 21.882 |
> | 8g | 96 T | N | 2.6790452 | 14.012 |
> | 8g | 96 T | C1 | 2.3044796 | 3.589 |
> | 8g | 96 T | C2 | 9.7585151 | 20.219 |
> | 16g | 1 T | N | 26.278 | 26.278 |
> | 16g | 32 T | N | 5.231374 | 26.417 |
> | 16g | 32 T | C1 | 5.6946983 | 6.538 |
> | 16g | 32 T | C2 | 21.8211105 | 41.133 |
> | 16g | 96 T | N | 6.2445556 | 27.141 |
> | 16g | 96 T | C1 | 4.6007096 | 6.259 |
> | 16g | 96 T | C2 | 19.2965783 | 39.007 |
> | 32g | 1 T | N | 48.149 | 48.149 |
> | 32g | 32 T | N | 10.7734677 | 61.643 |
> | 32g | 32 T | C1 | 10.1642097 | 10.903 |
> | 32g | 32 T | C2 | 43.8407607 | 88.152 |
> | 32g | 96 T | N | 13.1522042 | 61.432 |
> | 32g | 96 T | C1 | 9.0954641 | 9.885 |
> | 32g | 96 T | C2 | 38.9900931 | 80.574 |
> | 64g | 1 T | N | 100.583 | 100.583 |
> | 64g | 32 T | N | 20.9233744 | 134.701 |
> | 64g | 32 T | C1 | 18.5023784 | 19.358 |
> | 64g | 32 T | C2 | 86.4748377 | 172.707 |
> | 64g | 96 T | N | 26.7374116 | 126.08 |
> | 64g | 96 T | C1 | 16.8101551 | 17.938 |
> | 64g | 96 T | C2 | 80.1626621 | 169.003 |
> | 128g | 1 T | ...

This pull request has now been integrated.

Changeset: 31a307f2
Author:    Yi Yang <yyang at openjdk.org>
URL:       https://git.openjdk.org/jdk/commit/31a307f2fbe7b99435f50e5404c2a95f07b9a77b
Stats:     1512 lines in 16 files changed: 453 ins; 934 del; 125 mod

8306441: Two phase segmented heap dump

Co-authored-by: Kevin Walls <kevinw at openjdk.org>
Reviewed-by: amenkov, kevinw

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

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