Augustin Cavalier
4df505d911
This massively cuts down on lock contention in Add(), since insertions only acquire a write-lock in the case where a generation rolls over, same as Lookup() does. "git status" in buildtools, cold disk cache in a 4-core VM, seems about the same, maybe slightly slower (~0.5s seemed typical, out of 20-21s), while with a hot disk cache it's much faster: ~9.8s -> ~2.4s. Compile performance seemed about the same. Change-Id: Ia73f35fbbad3b3ac9ed783ea38cb8e2cb9818b5b Reviewed-on: https://review.haiku-os.org/c/haiku/+/9580 Tested-by: Commit checker robot <[email protected]> Reviewed-by: waddlesplash <[email protected]>
80 lines
2.1 KiB
C++
80 lines
2.1 KiB
C++
/*
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* Copyright 2025, Haiku, Inc. All rights reserved.
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* Distributed under the terms of the MIT License.
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*/
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#ifndef _KERNEL_UTIL_ATOMICS_HASH_TABLE_H
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#define _KERNEL_UTIL_ATOMICS_HASH_TABLE_H
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#include <util/OpenHashTable.h>
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#include <util/atomic.h>
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// AtomicsHashTable extends BOpenHashTable with some atomic operations.
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template<typename Definition, bool AutoExpand = true,
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bool CheckDuplicates = false>
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class AtomicsHashTable : public BOpenHashTable<Definition,
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AutoExpand, CheckDuplicates> {
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public:
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typedef BOpenHashTable<Definition, AutoExpand, CheckDuplicates> HashTable;
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typedef typename Definition::KeyType KeyType;
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typedef typename Definition::ValueType ValueType;
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AtomicsHashTable()
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: HashTable() {}
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AtomicsHashTable(const Definition& definition)
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: HashTable(definition) {}
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/*! \brief Inserts a value atomically.
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If there's another item with an identical key, the new value will not
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be inserted, and that value will be returned instead. If there's no
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other value with the same key, the passed value will be inserted,
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and NULL will be returned.
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The caller is responsible for ensuring that no Remove()s or Resize()s
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are invoked concurrently with this method.
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*/
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ValueType* InsertAtomic(ValueType* value)
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{
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KeyType key = HashTable::fDefinition.Key(value);
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size_t index = HashTable::fDefinition.Hash(value) & (HashTable::fTableSize - 1);
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HashTable::_Link(value) = NULL;
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ValueType** link = &HashTable::fTable[index];
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while (true) {
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ValueType* existing = atomic_pointer_get(link);
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if (existing == NULL) {
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existing = atomic_pointer_test_and_set(link, value, existing);
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if (existing == NULL) {
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size_t& count = HashTable::fItemCount;
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sizeof(size_t) == 4 ?
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atomic_add((int32*)&count, 1) :
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atomic_add64((int64*)&count, 1);
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return NULL;
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}
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}
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if (HashTable::fDefinition.Compare(key, existing))
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return existing;
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link = &HashTable::_Link(existing);
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}
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}
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bool ResizeIfNeeded()
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{
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size_t resizeNeeded = HashTable::ResizeNeeded();
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if (resizeNeeded == 0)
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return true;
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return HashTable::_Resize(resizeNeeded);
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}
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};
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#endif // _KERNEL_UTIL_ATOMICS_HASH_TABLE_H
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