weaselab/conflict-set
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maybeDecreaseCapacity policy was too strong

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We can allow larger capacities and still pay for the key bytes
This commit is contained in:
Andrew Noyes
2024-03-13 14:00:01 -07:00
parent c2606cd26a
commit 12540b8713
1 changed files with 4 additions and 3 deletions
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7
ConflictSet.cpp
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@@ -292,9 +292,10 @@ static_assert(kNode3Surplus >= kMinNodeSurplus);
static_assert(kBytesPerKey - sizeof(Node0) >= kMinNodeSurplus); static_assert(kBytesPerKey - sizeof(Node0) >= kMinNodeSurplus);
// setOldestVersion will additionally try to maintain this property: // setOldestVersion will additionally try to maintain this property:
// `max(children, 1) * length >= capacity` // `(children + entryPresent) * length >= capacity`
// //
// Which should give us the budget to pay for the key bytes // Which should give us the budget to pay for the key bytes. (children +
// entryPresent) is a lower bound on how many keys these bytes are a prefix of
template <class T, int64_t kMemoryBound = (1 << 20)> template <class T, int64_t kMemoryBound = (1 << 20)>
struct BoundedFreeListAllocator { struct BoundedFreeListAllocator {
@@ -910,7 +911,7 @@ void makeCapacityAtLeast(Node *&self, int capacity, NodeAllocators *allocators,
void maybeDecreaseCapacity(Node *&self, NodeAllocators *allocators, void maybeDecreaseCapacity(Node *&self, NodeAllocators *allocators,
ConflictSet::Impl *impl) { ConflictSet::Impl *impl) {
const int maxCapacity = const int maxCapacity =
std::max<int>(self->numChildren, 1) * self->partialKeyLen; (self->numChildren + int(self->entryPresent)) * self->partialKeyLen;
if (self->partialKeyCapacity <= maxCapacity) { if (self->partialKeyCapacity <= maxCapacity) {
return; return;
} }