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#pragma once
#include "defs.h"
#include "queue_chunk.h"
template <typename T, ui32 Size = 512, ui32 ConcurrencyFactor = 1, typename TChunk = TQueueChunk<T, Size>>
class TUnorderedCache : TNonCopyable {
static_assert(std::is_integral<T>::value || std::is_pointer<T>::value, "expect std::is_integral<T>::value || std::is_pointer<T>::value");
public:
static constexpr ui32 Concurrency = ConcurrencyFactor * 4;
private:
struct TReadSlot {
TChunk* volatile ReadFrom;
volatile ui32 ReadPosition;
char Padding[64 - sizeof(TChunk*) - sizeof(ui32)]; // 1 slot per cache line
};
struct TWriteSlot {
TChunk* volatile WriteTo;
volatile ui32 WritePosition;
char Padding[64 - sizeof(TChunk*) - sizeof(ui32)]; // 1 slot per cache line
};
static_assert(sizeof(TReadSlot) == 64, "expect sizeof(TReadSlot) == 64");
static_assert(sizeof(TWriteSlot) == 64, "expect sizeof(TWriteSlot) == 64");
private:
TReadSlot ReadSlots[Concurrency];
TWriteSlot WriteSlots[Concurrency];
static_assert(sizeof(TChunk*) == sizeof(TAtomic), "expect sizeof(TChunk*) == sizeof(TAtomic)");
private:
struct TLockedWriter {
TWriteSlot* Slot;
TChunk* WriteTo;
TLockedWriter()
: Slot(nullptr)
, WriteTo(nullptr)
{ }
TLockedWriter(TWriteSlot* slot, TChunk* writeTo)
: Slot(slot)
, WriteTo(writeTo)
{ }
~TLockedWriter() noexcept {
Drop();
}
void Drop() {
if (Slot) {
AtomicStore(&Slot->WriteTo, WriteTo);
Slot = nullptr;
}
}
TLockedWriter(const TLockedWriter&) = delete;
TLockedWriter& operator=(const TLockedWriter&) = delete;
TLockedWriter(TLockedWriter&& rhs)
: Slot(rhs.Slot)
, WriteTo(rhs.WriteTo)
{
rhs.Slot = nullptr;
}
TLockedWriter& operator=(TLockedWriter&& rhs) {
if (Y_LIKELY(this != &rhs)) {
Drop();
Slot = rhs.Slot;
WriteTo = rhs.WriteTo;
rhs.Slot = nullptr;
}
return *this;
}
};
private:
TLockedWriter LockWriter(ui64 writerRotation) {
ui32 cycle = 0;
for (;;) {
TWriteSlot* slot = &WriteSlots[writerRotation % Concurrency];
if (AtomicLoad(&slot->WriteTo) != nullptr) {
if (TChunk* writeTo = AtomicSwap(&slot->WriteTo, nullptr)) {
return TLockedWriter(slot, writeTo);
}
}
++writerRotation;
// Do a spinlock pause after a full cycle
if (++cycle == Concurrency) {
SpinLockPause();
cycle = 0;
}
}
}
void WriteOne(TLockedWriter& lock, T x) {
Y_DEBUG_ABORT_UNLESS(x != 0);
const ui32 pos = AtomicLoad(&lock.Slot->WritePosition);
if (pos != TChunk::EntriesCount) {
AtomicStore(&lock.Slot->WritePosition, pos + 1);
AtomicStore(&lock.WriteTo->Entries[pos], x);
} else {
TChunk* next = new TChunk();
AtomicStore(&next->Entries[0], x);
AtomicStore(&lock.Slot->WritePosition, 1u);
AtomicStore(&lock.WriteTo->Next, next);
lock.WriteTo = next;
}
}
public:
TUnorderedCache() {
for (ui32 i = 0; i < Concurrency; ++i) {
ReadSlots[i].ReadFrom = new TChunk();
ReadSlots[i].ReadPosition = 0;
WriteSlots[i].WriteTo = ReadSlots[i].ReadFrom;
WriteSlots[i].WritePosition = 0;
}
}
~TUnorderedCache() {
Y_ABORT_UNLESS(!Pop(0));
for (ui64 i = 0; i < Concurrency; ++i) {
if (ReadSlots[i].ReadFrom) {
delete ReadSlots[i].ReadFrom;
ReadSlots[i].ReadFrom = nullptr;
}
WriteSlots[i].WriteTo = nullptr;
}
}
T Pop(ui64 readerRotation) noexcept {
ui64 readerIndex = readerRotation;
const ui64 endIndex = readerIndex + Concurrency;
for (; readerIndex != endIndex; ++readerIndex) {
TReadSlot* slot = &ReadSlots[readerIndex % Concurrency];
if (AtomicLoad(&slot->ReadFrom) != nullptr) {
if (TChunk* readFrom = AtomicSwap(&slot->ReadFrom, nullptr)) {
const ui32 pos = AtomicLoad(&slot->ReadPosition);
if (pos != TChunk::EntriesCount) {
if (T ret = AtomicLoad(&readFrom->Entries[pos])) {
AtomicStore(&slot->ReadPosition, pos + 1);
AtomicStore(&slot->ReadFrom, readFrom); // release lock with same chunk
return ret; // found, return
} else {
AtomicStore(&slot->ReadFrom, readFrom); // release lock with same chunk
}
} else if (TChunk* next = AtomicLoad(&readFrom->Next)) {
if (T ret = AtomicLoad(&next->Entries[0])) {
AtomicStore(&slot->ReadPosition, 1u);
AtomicStore(&slot->ReadFrom, next); // release lock with next chunk
delete readFrom;
return ret;
} else {
AtomicStore(&slot->ReadPosition, 0u);
AtomicStore(&slot->ReadFrom, next); // release lock with new chunk
delete readFrom;
}
} else {
// nothing in old chunk and no next chunk, just release lock with old chunk
AtomicStore(&slot->ReadFrom, readFrom);
}
}
}
}
return 0; // got nothing after full cycle, return
}
void Push(T x, ui64 writerRotation) {
TLockedWriter lock = LockWriter(writerRotation);
WriteOne(lock, x);
}
void PushBulk(T* x, ui32 xcount, ui64 writerRotation) {
for (;;) {
// Fill no more then one queue chunk per round
const ui32 xround = Min(xcount, (ui32)TChunk::EntriesCount);
{
TLockedWriter lock = LockWriter(writerRotation++);
for (T* end = x + xround; x != end; ++x)
WriteOne(lock, *x);
}
if (xcount <= TChunk::EntriesCount)
break;
xcount -= TChunk::EntriesCount;
}
}
};
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