> This patch refines Parallel's sizing strategy to improve overall memory > management and performance. > > The young generation layout has been reconfigured from the previous > `eden-from/to` arrangement to a new `from/to-eden` order. This new layout > facilitates young generation resizing, since we perform resizing after a > successful young GC when all live objects are located at the beginning of the > young generation. Previously, resizing was often inhibited by live objects > residing in the middle of the young generation (from-space). The new layout > is illustrated in `parallelScavengeHeap.hpp`. > > `NumberSeq` is now used to track various runtime metrics, such as minor/major > GC pause durations, promoted/survived bytes after a young GC, highest old > generation usage, etc. This tracking primarily lives in `AdaptiveSizePolicy` > and its subclass `PSAdaptiveSizePolicy`. > > GC overhead checking, which was previously entangled with adaptive resizing > logic, has been extracted and is now largely encapsulated in > `ParallelScavengeHeap::is_gc_overhead_limit_reached`. > > ## Performance evaluation > > - SPECjvm2008-Compress shows ~8% improvement on Linux/AArch64 and Linux/x64 > (restoring the regression reported in > [JDK-8332485](https://bugs.openjdk.org/browse/JDK-8332485) and > [JDK-8338689](https://bugs.openjdk.org/browse/JDK-8338689)). > - Fixes the surprising behavior when using a non-default (smaller) value of > `GCTimeRatio` with Heapothesys/Hyperalloc, as discussed in [this > thread](https://mail.openjdk.org/pipermail/hotspot-gc-dev/2024-November/050146.html). > - Performance is mostly neutral across other tested benchmarks: **DaCapo**, > **SPECjbb2005**, **SPECjbb2015**, **SPECjvm2008**, and **CacheStress**. The > number of young-gc sometimes goes up a bit and the total heap-size decreases > a bit, because promotion-size-to-old-gen goes down with the more effective > eden/survivor-space resizing. > > PS: I have opportunistically set the obsolete/expired version to 25/26 for > now. I will update them accordingly before merging. > > Test: tier1-8
Albert Mingkun Yang has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains nine additional commits since the last revision: - Merge branch 'master' into pgc-size-policy - Merge branch 'master' into pgc-size-policy - review - Merge branch 'master' into pgc-size-policy - review - Merge branch 'master' into pgc-size-policy - review - Merge branch 'master' into pgc-size-policy - pgc-size-policy ------------- Changes: - all: https://git.openjdk.org/jdk/pull/25000/files - new: https://git.openjdk.org/jdk/pull/25000/files/320e590b..872b18bd Webrevs: - full: https://webrevs.openjdk.org/?repo=jdk&pr=25000&range=05 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=25000&range=04-05 Stats: 12205 lines in 260 files changed: 7807 ins; 3245 del; 1153 mod Patch: https://git.openjdk.org/jdk/pull/25000.diff Fetch: git fetch https://git.openjdk.org/jdk.git pull/25000/head:pull/25000 PR: https://git.openjdk.org/jdk/pull/25000
