weaselab/conflict-set
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WIP my understanding of the memory bound induction was wrong

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Andrew Noyes
2024-03-12 15:44:25 -07:00
parent aefb83dbc6
commit 75c304bbe7
1 changed files with 37 additions and 28 deletions
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63
ConflictSet.cpp
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@@ -261,17 +261,20 @@ struct Node256 : Node {
// Bound memory usage following the analysis in the ART paper
constexpr int kBytesPerKey = 121;
constexpr int kMinChildrenNode4 = 1;
constexpr int kBytesPerKey = 120;
constexpr int kMinChildrenNode4 = 2;
constexpr int kMinChildrenNode16 = 5;
constexpr int kMinChildrenNode48 = 17;
constexpr int kMinChildrenNode256 = 49;
static_assert(sizeof(Node256) < kMinChildrenNode256 * kBytesPerKey);
static_assert(sizeof(Node48) < kMinChildrenNode48 * kBytesPerKey);
static_assert(sizeof(Node16) < kMinChildrenNode16 * kBytesPerKey);
static_assert(sizeof(Node4) < kMinChildrenNode4 * kBytesPerKey);
static_assert(sizeof(Node0) < kBytesPerKey);
static_assert(sizeof(Node256) + kBytesPerKey <=
kMinChildrenNode256 * kBytesPerKey);
static_assert(sizeof(Node48) + kBytesPerKey <=
kMinChildrenNode48 * kBytesPerKey);
static_assert(sizeof(Node16) + kBytesPerKey <=
kMinChildrenNode16 * kBytesPerKey);
static_assert(sizeof(Node4) + kBytesPerKey <= kMinChildrenNode4 * kBytesPerKey);
static_assert(sizeof(Node0) <= kBytesPerKey);
// setOldestVersion will additionally try to maintain this property:
// `max(children, 1) * length >= capacity`
@@ -736,21 +739,14 @@ Node *nextLogical(Node *node) {
return node;
}
// Fix larger-than-desired capacities. Does not return nodes to freelists,
// since that wouldn't actually reclaim the memory used for partial key
// capacity.
void maybeDecreaseCapacity(Node *&self, NodeAllocators *allocators,
// Invalidates `self`, replacing it with a node of at least capacity.
// Does not return nodes to freelists.
void makeCapacityAtLeast(Node *&self, int capacity, NodeAllocators *allocators,
ConflictSet::Impl *impl) {
const int maxCapacity =
std::max<int>(self->numChildren, 1) * self->partialKeyLen;
if (self->partialKeyCapacity <= maxCapacity) {
return;
}
switch (self->type) {
case Type::Node0: {
auto *self0 = (Node0 *)self;
auto *newSelf = allocators->node0.allocate(maxCapacity);
auto *newSelf = allocators->node0.allocate(capacity);
memcpy((char *)newSelf + kNodeCopyBegin, (char *)self + kNodeCopyBegin,
kNodeCopySize);
memcpy(newSelf->partialKey(), self0->partialKey(), self->partialKeyLen);
@@ -760,7 +756,7 @@ void maybeDecreaseCapacity(Node *&self, NodeAllocators *allocators,
} break;
case Type::Node4: {
auto *self4 = (Node4 *)self;
auto *newSelf = allocators->node4.allocate(maxCapacity);
auto *newSelf = allocators->node4.allocate(capacity);
memcpy((char *)newSelf + kNodeCopyBegin, (char *)self + kNodeCopyBegin,
kNodeCopySize);
memcpy(newSelf->partialKey(), self4->partialKey(), self->partialKeyLen);
@@ -776,7 +772,7 @@ void maybeDecreaseCapacity(Node *&self, NodeAllocators *allocators,
} break;
case Type::Node16: {
auto *self16 = (Node16 *)self;
auto *newSelf = allocators->node16.allocate(maxCapacity);
auto *newSelf = allocators->node16.allocate(capacity);
memcpy((char *)newSelf + kNodeCopyBegin, (char *)self + kNodeCopyBegin,
kNodeCopySize);
memcpy(newSelf->partialKey(), self16->partialKey(), self->partialKeyLen);
@@ -792,7 +788,7 @@ void maybeDecreaseCapacity(Node *&self, NodeAllocators *allocators,
} break;
case Type::Node48: {
auto *self48 = (Node48 *)self;
auto *newSelf = allocators->node48.allocate(maxCapacity);
auto *newSelf = allocators->node48.allocate(capacity);
memcpy((char *)newSelf + kNodeCopyBegin, (char *)self + kNodeCopyBegin,
kNodeCopySize);
memcpy(newSelf->partialKey(), self48->partialKey(), self->partialKeyLen);
@@ -812,7 +808,7 @@ void maybeDecreaseCapacity(Node *&self, NodeAllocators *allocators,
} break;
case Type::Node256: {
auto *self256 = (Node256 *)self;
auto *newSelf = allocators->node256.allocate(maxCapacity);
auto *newSelf = allocators->node256.allocate(capacity);
memcpy((char *)newSelf + kNodeCopyBegin, (char *)self + kNodeCopyBegin,
kNodeCopySize);
memcpy(newSelf->partialKey(), self256->partialKey(), self->partialKeyLen);
@@ -827,6 +823,19 @@ void maybeDecreaseCapacity(Node *&self, NodeAllocators *allocators,
}
}
// Fix larger-than-desired capacities. Does not return nodes to freelists,
// since that wouldn't actually reclaim the memory used for partial key
// capacity.
void maybeDecreaseCapacity(Node *&self, NodeAllocators *allocators,
ConflictSet::Impl *impl) {
const int maxCapacity =
std::max<int>(self->numChildren, 1) * self->partialKeyLen;
if (self->partialKeyCapacity <= maxCapacity) {
return;
}
makeCapacityAtLeast(self, maxCapacity, allocators, impl);
}
// TODO fuse into erase child so we don't need to repeat branches on type
void maybeDownsize(Node *self, NodeAllocators *allocators,
ConflictSet::Impl *impl, Node *&dontInvalidate) {
@@ -885,7 +894,7 @@ void maybeDownsize(Node *self, NodeAllocators *allocators,
}
} break;
case Type::Node16:
if (self->numChildren < kMinChildrenNode16) {
if (self->numChildren + int(self->entryPresent) < kMinChildrenNode16) {
auto *self16 = (Node16 *)self;
auto *newSelf = allocators->node4.allocate(self->partialKeyLen);
memcpy((char *)newSelf + kNodeCopyBegin, (char *)self + kNodeCopyBegin,
@@ -902,7 +911,7 @@ void maybeDownsize(Node *self, NodeAllocators *allocators,
}
break;
case Type::Node48:
if (self->numChildren < kMinChildrenNode48) {
if (self->numChildren + int(self->entryPresent) < kMinChildrenNode48) {
auto *self48 = (Node48 *)self;
auto *newSelf = allocators->node16.allocate(self->partialKeyLen);
memcpy((char *)newSelf + kNodeCopyBegin, (char *)self + kNodeCopyBegin,
@@ -915,7 +924,7 @@ void maybeDownsize(Node *self, NodeAllocators *allocators,
// Suppress a false positive -Waggressive-loop-optimizations warning
// in gcc. `assume` doesn't work for some reason.
if (!(i < 16)) {
__builtin_unreachable();
__builtin_unreachable(); // GCOVR_EXCL_LINE
}
newSelf->index[i] = c;
newSelf->children[i] = self48->children[self48->index[c]];
@@ -929,7 +938,7 @@ void maybeDownsize(Node *self, NodeAllocators *allocators,
}
break;
case Type::Node256:
if (self->numChildren < kMinChildrenNode256) {
if (self->numChildren + int(self->entryPresent) < kMinChildrenNode256) {
auto *self256 = (Node256 *)self;
auto *newSelf = allocators->node48.allocate(self->partialKeyLen);
memcpy((char *)newSelf + kNodeCopyBegin, (char *)self + kNodeCopyBegin,
@@ -2500,7 +2509,7 @@ Iterator firstGeq(Node *n, std::string_view key) {
minNumChildren = kMinChildrenNode256;
break;
}
if (node->numChildren < minNumChildren) {
if (node->numChildren + int(node->entryPresent) < minNumChildren) {
fprintf(stderr,
"%s has %d children, which is less than the minimum required %d\n",
getSearchPathPrintable(node).c_str(), node->numChildren,