weaselab/versioned-map
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Prevent unnecessary rotations

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This commit is contained in:
Andrew Noyes
2024-05-14 10:26:40 -07:00
parent 9834b2e811
commit b3ad250f41
1 changed files with 12 additions and 9 deletions
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21
VersionedMap.cpp
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@@ -690,8 +690,9 @@ struct __attribute__((__visibility__("hidden"))) VersionedMap::Impl {
template <std::memory_order kOrder, class T>
void search(Key key, T root, int64_t version, Finger &finger) const {
finger.clear();
// Prevent integer promotion etc
static_assert(std::is_same_v<T, uint32_t>);
finger.clear();
if (root == 0) {
return;
}
@@ -746,7 +747,7 @@ struct __attribute__((__visibility__("hidden"))) VersionedMap::Impl {
finger.copyTo(copy);
move<std::memory_order_relaxed>(copy, latestVersion, true);
if (copy.searchPathSize() == 0) {
rangeVersion = -1;
rangeVersion = -1; // Sentinel for "no mutation ending here"
} else {
rangeVersion = mm.base[copy.backNode()].entry->rangeVersion;
}
@@ -757,8 +758,8 @@ struct __attribute__((__visibility__("hidden"))) VersionedMap::Impl {
} else {
rangeVersion = latestVersion;
if (inserted) {
val = {nullptr, -1};
pointVersion = -1;
val = {nullptr, -1}; // Sentinel for "no point mutation here"
pointVersion = -1; // Sentinel for "no point mutation here"
} else {
auto *entry = mm.base[finger.backNode()].entry;
val = {entry->getVal(), entry->valLen};
@@ -767,8 +768,9 @@ struct __attribute__((__visibility__("hidden"))) VersionedMap::Impl {
}
// Prepare new node
uint32_t node =
newNode(pointVersion, rangeVersion, key.p, key.len, val->p, val->len);
uint32_t node = newNode(
pointVersion, rangeVersion, key.p, key.len, val->p, val->len,
inserted ? random.next() : mm.base[finger.backNode()].entry->priority);
if (!inserted) {
auto &n = mm.base[node];
n.pointer[0] = child<std::memory_order_relaxed>(finger.backNode(), false,
@@ -881,15 +883,16 @@ struct __attribute__((__visibility__("hidden"))) VersionedMap::Impl {
}
uint32_t newNode(int64_t version, int64_t rangeVersion, const uint8_t *key,
int keyLen, const uint8_t *val, int valLen) {
int keyLen, const uint8_t *val, int valLen,
uint32_t priority) {
auto result = mm.allocate();
auto &node = mm.base[result];
node.updateVersion = version;
node.pointer[0] = 0;
node.pointer[1] = 0;
node.updated.store(false, std::memory_order_relaxed);
node.entry = Entry::make(version, rangeVersion, key, keyLen, val, valLen,
random.next());
node.entry =
Entry::make(version, rangeVersion, key, keyLen, val, valLen, priority);
return result;
}