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8374695: ZGC: Convert zTLABUsage to use Atomic<T>

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Reviewed-by: stefank, tschatzl
This commit is contained in:
Axel Boldt-Christmas 2026-01-27 10:26:29 +00:00
parent e0445c09f7
commit b1aea55205
2 changed files with 9 additions and 9 deletions
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11
src/hotspot/share/gc/z/zTLABUsage.cpp
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@ -1,5 +1,5 @@
/* /*
* Copyright (c) 2025, Oracle and/or its affiliates. All rights reserved. * Copyright (c) 2025, 2026, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
* *
* This code is free software; you can redistribute it and/or modify it * This code is free software; you can redistribute it and/or modify it
@ -23,24 +23,23 @@
#include "gc/z/zTLABUsage.hpp" #include "gc/z/zTLABUsage.hpp"
#include "logging/log.hpp" #include "logging/log.hpp"
#include "runtime/atomicAccess.hpp"
ZTLABUsage::ZTLABUsage() ZTLABUsage::ZTLABUsage()
: _used(0), : _used(0),
_used_history() {} _used_history() {}
void ZTLABUsage::increase_used(size_t size) { void ZTLABUsage::increase_used(size_t size) {
AtomicAccess::add(&_used, size, memory_order_relaxed); _used.add_then_fetch(size, memory_order_relaxed);
} }
void ZTLABUsage::decrease_used(size_t size) { void ZTLABUsage::decrease_used(size_t size) {
precond(size <= _used); precond(size <= _used.load_relaxed());
AtomicAccess::sub(&_used, size, memory_order_relaxed); _used.sub_then_fetch(size, memory_order_relaxed);
} }
void ZTLABUsage::reset() { void ZTLABUsage::reset() {
const size_t used = AtomicAccess::xchg(&_used, (size_t) 0); const size_t used = _used.exchange(0u);
// Avoid updates when nothing has been allocated since the last YC // Avoid updates when nothing has been allocated since the last YC
if (used == 0) { if (used == 0) {

7
src/hotspot/share/gc/z/zTLABUsage.hpp
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@ -1,5 +1,5 @@
/* /*
* Copyright (c) 2025, Oracle and/or its affiliates. All rights reserved. * Copyright (c) 2025, 2026, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
* *
* This code is free software; you can redistribute it and/or modify it * This code is free software; you can redistribute it and/or modify it
@ -24,6 +24,7 @@
#ifndef SHARE_GC_Z_ZTLABUSAGE_HPP #ifndef SHARE_GC_Z_ZTLABUSAGE_HPP
#define SHARE_GC_Z_ZTLABUSAGE_HPP #define SHARE_GC_Z_ZTLABUSAGE_HPP
#include "runtime/atomic.hpp"
#include "utilities/globalDefinitions.hpp" #include "utilities/globalDefinitions.hpp"
#include "utilities/numberSeq.hpp" #include "utilities/numberSeq.hpp"
@ -42,9 +43,9 @@
class ZTLABUsage { class ZTLABUsage {
private: private:
// Accounting TLAB used until the next GC cycle // Accounting TLAB used until the next GC cycle
volatile size_t _used; Atomic<size_t> _used;
// Sequence of historic used values // Sequence of historic used values
TruncatedSeq _used_history; TruncatedSeq _used_history;
public: public:
ZTLABUsage(); ZTLABUsage();