RFR: JDK-8298138: Shenandoah: HdrSeq asserts "sub-bucket index (512) overflow for value ( 1.00)"

[Roman Kennke]

On Tue, 6 Dec 2022 03:46:12 GMT, Y. Srinivas Ramakrishna <ysr at openjdk.org> wrote:

> JBS link: https://bugs.openjdk.org/browse/JDK-8298138
> - Fixed a boundary condition that was triggering an assert.
> - Added a simple-minded gtest for HdrSeq, which allows one to exercise the asserting code in a debug build.
> - Tested with: `CONF=slowdebug make run-test TEST="gtest:BasicShenandoahNumberSeqTest"`

Hi Ramki,
The change looks good. I have a few minor comments.

src/hotspot/share/gc/shenandoah/shenandoahNumberSeq.hpp line 58:

> 56: // It has very low memory requirements, and is thread-safe. When accuracy
> 57: // is not needed, it is preferred over HdrSeq.
> 58: class BinaryMagnitudeSeq : public CHeapObj<mtInternal> {

What is the relevance of this change? Also, if it *is* necessary, then it should be mtGC.

test/hotspot/gtest/gc/shenandoah/test_shenandoahNumberSeq.cpp line 2:

> 1: /*
> 2:  * Copyright (c) 2016, 2017, Oracle and/or its affiliates. All rights reserved.

The copyright should be 2022.

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Changes requested by rkennke (Reviewer).

PR: https://git.openjdk.org/jdk/pull/11524