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// Copyright 2017 Yahoo Holdings. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
#pragma once
#include <cstddef>
#include <vector>
namespace vespalib::datastore {
/**
* Config specifying layout and buffer allocation strategy for an array store.
*/
class ArrayStoreConfig
{
public:
/**
* Specification of buffer allocation strategy for arrays of a given size.
*/
struct AllocSpec {
// Minimum number of arrays to allocate in a buffer.
size_t minArraysInBuffer;
// Maximum number of arrays to allocate in a buffer.
size_t maxArraysInBuffer;
// Number of arrays needed before allocating a new buffer instead of just resizing the first one.
size_t numArraysForNewBuffer;
// Grow factor used when allocating a new buffer.
float allocGrowFactor;
AllocSpec(size_t minArraysInBuffer_,
size_t maxArraysInBuffer_,
size_t numArraysForNewBuffer_,
float allocGrowFactor_)
: minArraysInBuffer(minArraysInBuffer_),
maxArraysInBuffer(maxArraysInBuffer_),
numArraysForNewBuffer(numArraysForNewBuffer_),
allocGrowFactor(allocGrowFactor_) {}
};
using AllocSpecVector = std::vector<AllocSpec>;
private:
AllocSpecVector _allocSpecs;
bool _enable_free_lists;
/**
* Setup an array store with arrays of size [1-(allocSpecs.size()-1)] allocated in buffers and
* larger arrays are heap allocated. The allocation spec for a given array size is found in the given vector.
* Allocation spec for large arrays is located at position 0.
*/
ArrayStoreConfig(const AllocSpecVector &allocSpecs);
public:
/**
* Setup an array store with arrays of size [1-maxSmallArraySize] allocated in buffers
* with the given default allocation spec. Larger arrays are heap allocated.
*/
ArrayStoreConfig(size_t maxSmallArraySize, const AllocSpec &defaultSpec);
size_t maxSmallArraySize() const { return _allocSpecs.size() - 1; }
const AllocSpec &specForSize(size_t arraySize) const;
ArrayStoreConfig& enable_free_lists(bool enable) & noexcept {
_enable_free_lists = enable;
return *this;
}
ArrayStoreConfig&& enable_free_lists(bool enable) && noexcept {
_enable_free_lists = enable;
return std::move(*this);
}
[[nodiscard]] bool enable_free_lists() const noexcept { return _enable_free_lists; }
/**
* Generate a config that is optimized for the given memory huge page size.
*/
static ArrayStoreConfig optimizeForHugePage(size_t maxSmallArraySize,
size_t hugePageSize,
size_t smallPageSize,
size_t entrySize,
size_t maxEntryRefOffset,
size_t minNumArraysForNewBuffer,
float allocGrowFactor);
};
}
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