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chore: remove duplicate code from dash and simplify #2765

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merged 1 commit into from
Mar 29, 2024
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chore: remove duplicate code from dash and simplify #2765

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36 changes: 12 additions & 24 deletions src/core/dash.h
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Original file line number Diff line number Diff line change
Expand Up @@ -34,33 +34,21 @@ class DashTable : public detail::DashTableBase {
DashTable(const DashTable&) = delete;
DashTable& operator=(const DashTable&) = delete;

struct SegmentPolicy {
static constexpr unsigned NUM_SLOTS = Policy::kSlotNum;
static constexpr unsigned BUCKET_CNT = Policy::kBucketNum;
static constexpr unsigned STASH_BUCKET_NUM = Policy::kStashBucketNum;
static constexpr bool USE_VERSION = Policy::kUseVersion;
};

using Base = detail::DashTableBase;
using SegmentType = detail::Segment<_Key, _Value, SegmentPolicy>;
using SegmentType = detail::Segment<_Key, _Value, Policy>;
using SegmentIterator = typename SegmentType::Iterator;

public:
using Key_t = _Key;
using Value_t = _Value;
using Segment_t = SegmentType;

//! Number of "official" buckets that are used to position a key. In other words, does not include
//! stash buckets.
static constexpr unsigned kLogicalBucketNum = Policy::kBucketNum;

//! Total number of buckets in a segment (including stash).
static constexpr unsigned kPhysicalBucketNum = SegmentType::kTotalBuckets;
static constexpr unsigned kBucketWidth = Policy::kSlotNum;
static constexpr double kTaxAmount = SegmentType::kTaxSize;
static constexpr size_t kSegBytes = sizeof(SegmentType);
static constexpr size_t kSegCapacity = SegmentType::capacity();
static constexpr bool kUseVersion = Policy::kUseVersion;
static constexpr size_t kSlotNum = SegmentType::kSlotNum;
static constexpr size_t kBucketNum = SegmentType::kBucketNum;

// if IsSingleBucket is true - iterates only over a single bucket.
template <bool IsConst, bool IsSingleBucket = false> class Iterator;
Expand Down Expand Up @@ -556,11 +544,11 @@ void DashTable<_Key, _Value, Policy>::CVCUponInsert(uint64_t ver_threshold, cons
return;
}

static_assert(kPhysicalBucketNum < 0xFF, "");
static_assert(SegmentType::kTotalBuckets < 0xFF, "");

// Segment is full, we need to return the whole segment, because it can be split
// and its entries can be reshuffled into different buckets.
for (uint8_t i = 0; i < kPhysicalBucketNum; ++i) {
for (uint8_t i = 0; i < SegmentType::kTotalBuckets; ++i) {
if (target->GetVersion(i) < ver_threshold && !target->GetBucket(i).IsEmpty()) {
cb(bucket_iterator{this, seg_id, i});
}
Expand Down Expand Up @@ -646,8 +634,8 @@ bool DashTable<_Key, _Value, Policy>::ShiftRight(bucket_iterator it) {
typename Segment_t::Hash_t hash_val = 0;
auto& bucket = seg->GetBucket(it.bucket_id_);

if (bucket.GetBusy() & (1 << (kBucketWidth - 1))) {
it.slot_id_ = kBucketWidth - 1;
if (bucket.GetBusy() & (1 << (kSlotNum - 1))) {
it.slot_id_ = kSlotNum - 1;
hash_val = DoHash(it->first);
policy_.DestroyKey(it->first);
policy_.DestroyValue(it->second);
Expand Down Expand Up @@ -800,7 +788,7 @@ auto DashTable<_Key, _Value, Policy>::InsertInternal(U&& key, V&& value, Evictio

for (unsigned i = 0; i < Policy::kStashBucketNum; ++i) {
hotspot.probes.by_type.stash_buckets[i] =
bucket_iterator{this, target_seg_id, uint8_t(kLogicalBucketNum + i), 0};
bucket_iterator{this, target_seg_id, uint8_t(Policy::kBucketNum + i), 0};
}
hotspot.num_buckets = HotspotBuckets::kNumBuckets;

Expand Down Expand Up @@ -910,7 +898,7 @@ auto DashTable<_Key, _Value, Policy>::TraverseBySegmentOrder(Cursor curs, Cb&& c
s->TraverseBucket(bid, std::move(dt_cb));

++bid;
if (bid == kPhysicalBucketNum) {
if (bid == SegmentType::kTotalBuckets) {
sid = NextSeg(sid);
bid = 0;
if (sid >= segment_.size()) {
Expand All @@ -924,15 +912,15 @@ auto DashTable<_Key, _Value, Policy>::TraverseBySegmentOrder(Cursor curs, Cb&& c
template <typename _Key, typename _Value, typename Policy>
auto DashTable<_Key, _Value, Policy>::GetRandomCursor(absl::BitGen* bitgen) -> Cursor {
uint32_t sid = absl::Uniform<uint32_t>(*bitgen, 0, segment_.size());
uint8_t bid = absl::Uniform<uint8_t>(*bitgen, 0, kLogicalBucketNum);
uint8_t bid = absl::Uniform<uint8_t>(*bitgen, 0, Policy::kBucketNum);

return Cursor{global_depth_, sid, bid};
}

template <typename _Key, typename _Value, typename Policy>
template <typename Cb>
auto DashTable<_Key, _Value, Policy>::Traverse(Cursor curs, Cb&& cb) -> Cursor {
if (curs.bucket_id() >= kLogicalBucketNum) // sanity.
if (curs.bucket_id() >= Policy::kBucketNum) // sanity.
return 0;

uint32_t sid = curs.segment_id(global_depth_);
Expand All @@ -955,7 +943,7 @@ auto DashTable<_Key, _Value, Policy>::Traverse(Cursor curs, Cb&& cb) -> Cursor {
sid = 0;
++bid;

if (bid >= kLogicalBucketNum)
if (bid >= Policy::kBucketNum)
return 0; // "End of traversal" cursor.
}
} while (!fetched);
Expand Down
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