accelerate-1.4.0.0: cbits/tracy/public/client/tracy_concurrentqueue.h
// Provides a C++11 implementation of a multi-producer, multi-consumer lock-free queue.
// An overview, including benchmark results, is provided here:
// http://moodycamel.com/blog/2014/a-fast-general-purpose-lock-free-queue-for-c++
// The full design is also described in excruciating detail at:
// http://moodycamel.com/blog/2014/detailed-design-of-a-lock-free-queue
// Simplified BSD license:
// Copyright (c) 2013-2016, Cameron Desrochers.
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without modification,
// are permitted provided that the following conditions are met:
//
// - Redistributions of source code must retain the above copyright notice, this list of
// conditions and the following disclaimer.
// - Redistributions in binary form must reproduce the above copyright notice, this list of
// conditions and the following disclaimer in the documentation and/or other materials
// provided with the distribution.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
// MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
// THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
// OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
// HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR
// TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
// EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#pragma once
#include "../common/TracyAlloc.hpp"
#include "../common/TracyForceInline.hpp"
#include "../common/TracySystem.hpp"
#if defined(__GNUC__)
// Disable -Wconversion warnings (spuriously triggered when Traits::size_t and
// Traits::index_t are set to < 32 bits, causing integer promotion, causing warnings
// upon assigning any computed values)
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wconversion"
#endif
#if defined(__APPLE__)
#include "TargetConditionals.h"
#endif
#include <atomic> // Requires C++11. Sorry VS2010.
#include <cassert>
#include <cstddef> // for max_align_t
#include <cstdint>
#include <cstdlib>
#include <type_traits>
#include <algorithm>
#include <utility>
#include <limits>
#include <climits> // for CHAR_BIT
#include <array>
#include <thread> // partly for __WINPTHREADS_VERSION if on MinGW-w64 w/ POSIX threading
namespace tracy
{
// Compiler-specific likely/unlikely hints
namespace moodycamel { namespace details {
#if defined(__GNUC__)
inline bool cqLikely(bool x) { return __builtin_expect((x), true); }
inline bool cqUnlikely(bool x) { return __builtin_expect((x), false); }
#else
inline bool cqLikely(bool x) { return x; }
inline bool cqUnlikely(bool x) { return x; }
#endif
} }
namespace
{
// to avoid MSVC warning 4127: conditional expression is constant
template <bool>
struct compile_time_condition
{
static const bool value = false;
};
template <>
struct compile_time_condition<true>
{
static const bool value = true;
};
}
namespace moodycamel {
namespace details {
template<typename T>
struct const_numeric_max {
static_assert(std::is_integral<T>::value, "const_numeric_max can only be used with integers");
static const T value = std::numeric_limits<T>::is_signed
? (static_cast<T>(1) << (sizeof(T) * CHAR_BIT - 1)) - static_cast<T>(1)
: static_cast<T>(-1);
};
#if defined(__GLIBCXX__)
typedef ::max_align_t std_max_align_t; // libstdc++ forgot to add it to std:: for a while
#else
typedef std::max_align_t std_max_align_t; // Others (e.g. MSVC) insist it can *only* be accessed via std::
#endif
// Some platforms have incorrectly set max_align_t to a type with <8 bytes alignment even while supporting
// 8-byte aligned scalar values (*cough* 32-bit iOS). Work around this with our own union. See issue #64.
typedef union {
std_max_align_t x;
long long y;
void* z;
} max_align_t;
}
// Default traits for the ConcurrentQueue. To change some of the
// traits without re-implementing all of them, inherit from this
// struct and shadow the declarations you wish to be different;
// since the traits are used as a template type parameter, the
// shadowed declarations will be used where defined, and the defaults
// otherwise.
struct ConcurrentQueueDefaultTraits
{
// General-purpose size type. std::size_t is strongly recommended.
typedef std::size_t size_t;
// The type used for the enqueue and dequeue indices. Must be at least as
// large as size_t. Should be significantly larger than the number of elements
// you expect to hold at once, especially if you have a high turnover rate;
// for example, on 32-bit x86, if you expect to have over a hundred million
// elements or pump several million elements through your queue in a very
// short space of time, using a 32-bit type *may* trigger a race condition.
// A 64-bit int type is recommended in that case, and in practice will
// prevent a race condition no matter the usage of the queue. Note that
// whether the queue is lock-free with a 64-int type depends on the whether
// std::atomic<std::uint64_t> is lock-free, which is platform-specific.
typedef std::size_t index_t;
// Internally, all elements are enqueued and dequeued from multi-element
// blocks; this is the smallest controllable unit. If you expect few elements
// but many producers, a smaller block size should be favoured. For few producers
// and/or many elements, a larger block size is preferred. A sane default
// is provided. Must be a power of 2.
static const size_t BLOCK_SIZE = 64*1024;
// For explicit producers (i.e. when using a producer token), the block is
// checked for being empty by iterating through a list of flags, one per element.
// For large block sizes, this is too inefficient, and switching to an atomic
// counter-based approach is faster. The switch is made for block sizes strictly
// larger than this threshold.
static const size_t EXPLICIT_BLOCK_EMPTY_COUNTER_THRESHOLD = 32;
// How many full blocks can be expected for a single explicit producer? This should
// reflect that number's maximum for optimal performance. Must be a power of 2.
static const size_t EXPLICIT_INITIAL_INDEX_SIZE = 32;
// Controls the number of items that an explicit consumer (i.e. one with a token)
// must consume before it causes all consumers to rotate and move on to the next
// internal queue.
static const std::uint32_t EXPLICIT_CONSUMER_CONSUMPTION_QUOTA_BEFORE_ROTATE = 256;
// The maximum number of elements (inclusive) that can be enqueued to a sub-queue.
// Enqueue operations that would cause this limit to be surpassed will fail. Note
// that this limit is enforced at the block level (for performance reasons), i.e.
// it's rounded up to the nearest block size.
static const size_t MAX_SUBQUEUE_SIZE = details::const_numeric_max<size_t>::value;
// Memory allocation can be customized if needed.
// malloc should return nullptr on failure, and handle alignment like std::malloc.
#if defined(malloc) || defined(free)
// Gah, this is 2015, stop defining macros that break standard code already!
// Work around malloc/free being special macros:
static inline void* WORKAROUND_malloc(size_t size) { return malloc(size); }
static inline void WORKAROUND_free(void* ptr) { return free(ptr); }
static inline void* (malloc)(size_t size) { return WORKAROUND_malloc(size); }
static inline void (free)(void* ptr) { return WORKAROUND_free(ptr); }
#else
static inline void* malloc(size_t size) { return tracy::tracy_malloc(size); }
static inline void free(void* ptr) { return tracy::tracy_free(ptr); }
#endif
};
// When producing or consuming many elements, the most efficient way is to:
// 1) Use one of the bulk-operation methods of the queue with a token
// 2) Failing that, use the bulk-operation methods without a token
// 3) Failing that, create a token and use that with the single-item methods
// 4) Failing that, use the single-parameter methods of the queue
// Having said that, don't create tokens willy-nilly -- ideally there should be
// a maximum of one token per thread (of each kind).
struct ProducerToken;
struct ConsumerToken;
template<typename T, typename Traits> class ConcurrentQueue;
namespace details
{
struct ConcurrentQueueProducerTypelessBase
{
ConcurrentQueueProducerTypelessBase* next;
std::atomic<bool> inactive;
ProducerToken* token;
uint32_t threadId;
ConcurrentQueueProducerTypelessBase()
: next(nullptr), inactive(false), token(nullptr), threadId(0)
{
}
};
template<typename T>
static inline bool circular_less_than(T a, T b)
{
static_assert(std::is_integral<T>::value && !std::numeric_limits<T>::is_signed, "circular_less_than is intended to be used only with unsigned integer types");
return static_cast<T>(a - b) > static_cast<T>(static_cast<T>(1) << (static_cast<T>(sizeof(T) * CHAR_BIT - 1)));
// Note: extra parens around rhs of operator<< is MSVC bug: https://developercommunity2.visualstudio.com/t/C4554-triggers-when-both-lhs-and-rhs-is/10034931
// silencing the bug requires #pragma warning(disable: 4554) around the calling code and has no effect when done here.
}
template<typename U>
static inline char* align_for(char* ptr)
{
const std::size_t alignment = std::alignment_of<U>::value;
return ptr + (alignment - (reinterpret_cast<std::uintptr_t>(ptr) % alignment)) % alignment;
}
template<typename T>
static inline T ceil_to_pow_2(T x)
{
static_assert(std::is_integral<T>::value && !std::numeric_limits<T>::is_signed, "ceil_to_pow_2 is intended to be used only with unsigned integer types");
// Adapted from http://graphics.stanford.edu/~seander/bithacks.html#RoundUpPowerOf2
--x;
x |= x >> 1;
x |= x >> 2;
x |= x >> 4;
for (std::size_t i = 1; i < sizeof(T); i <<= 1) {
x |= x >> (i << 3);
}
++x;
return x;
}
template<typename T>
static inline void swap_relaxed(std::atomic<T>& left, std::atomic<T>& right)
{
T temp = std::move(left.load(std::memory_order_relaxed));
left.store(std::move(right.load(std::memory_order_relaxed)), std::memory_order_relaxed);
right.store(std::move(temp), std::memory_order_relaxed);
}
template<typename T>
static inline T const& nomove(T const& x)
{
return x;
}
template<bool Enable>
struct nomove_if
{
template<typename T>
static inline T const& eval(T const& x)
{
return x;
}
};
template<>
struct nomove_if<false>
{
template<typename U>
static inline auto eval(U&& x)
-> decltype(std::forward<U>(x))
{
return std::forward<U>(x);
}
};
template<typename It>
static inline auto deref_noexcept(It& it) noexcept -> decltype(*it)
{
return *it;
}
#if defined(__clang__) || !defined(__GNUC__) || __GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 8)
template<typename T> struct is_trivially_destructible : std::is_trivially_destructible<T> { };
#else
template<typename T> struct is_trivially_destructible : std::has_trivial_destructor<T> { };
#endif
template<typename T> struct static_is_lock_free_num { enum { value = 0 }; };
template<> struct static_is_lock_free_num<signed char> { enum { value = ATOMIC_CHAR_LOCK_FREE }; };
template<> struct static_is_lock_free_num<short> { enum { value = ATOMIC_SHORT_LOCK_FREE }; };
template<> struct static_is_lock_free_num<int> { enum { value = ATOMIC_INT_LOCK_FREE }; };
template<> struct static_is_lock_free_num<long> { enum { value = ATOMIC_LONG_LOCK_FREE }; };
template<> struct static_is_lock_free_num<long long> { enum { value = ATOMIC_LLONG_LOCK_FREE }; };
template<typename T> struct static_is_lock_free : static_is_lock_free_num<typename std::make_signed<T>::type> { };
template<> struct static_is_lock_free<bool> { enum { value = ATOMIC_BOOL_LOCK_FREE }; };
template<typename U> struct static_is_lock_free<U*> { enum { value = ATOMIC_POINTER_LOCK_FREE }; };
}
struct ProducerToken
{
template<typename T, typename Traits>
explicit ProducerToken(ConcurrentQueue<T, Traits>& queue);
ProducerToken(ProducerToken&& other) noexcept
: producer(other.producer)
{
other.producer = nullptr;
if (producer != nullptr) {
producer->token = this;
}
}
inline ProducerToken& operator=(ProducerToken&& other) noexcept
{
swap(other);
return *this;
}
void swap(ProducerToken& other) noexcept
{
std::swap(producer, other.producer);
if (producer != nullptr) {
producer->token = this;
}
if (other.producer != nullptr) {
other.producer->token = &other;
}
}
// A token is always valid unless:
// 1) Memory allocation failed during construction
// 2) It was moved via the move constructor
// (Note: assignment does a swap, leaving both potentially valid)
// 3) The associated queue was destroyed
// Note that if valid() returns true, that only indicates
// that the token is valid for use with a specific queue,
// but not which one; that's up to the user to track.
inline bool valid() const { return producer != nullptr; }
~ProducerToken()
{
if (producer != nullptr) {
producer->token = nullptr;
producer->inactive.store(true, std::memory_order_release);
}
}
// Disable copying and assignment
ProducerToken(ProducerToken const&) = delete;
ProducerToken& operator=(ProducerToken const&) = delete;
private:
template<typename T, typename Traits> friend class ConcurrentQueue;
protected:
details::ConcurrentQueueProducerTypelessBase* producer;
};
struct ConsumerToken
{
template<typename T, typename Traits>
explicit ConsumerToken(ConcurrentQueue<T, Traits>& q);
ConsumerToken(ConsumerToken&& other) noexcept
: initialOffset(other.initialOffset), lastKnownGlobalOffset(other.lastKnownGlobalOffset), itemsConsumedFromCurrent(other.itemsConsumedFromCurrent), currentProducer(other.currentProducer), desiredProducer(other.desiredProducer)
{
}
inline ConsumerToken& operator=(ConsumerToken&& other) noexcept
{
swap(other);
return *this;
}
void swap(ConsumerToken& other) noexcept
{
std::swap(initialOffset, other.initialOffset);
std::swap(lastKnownGlobalOffset, other.lastKnownGlobalOffset);
std::swap(itemsConsumedFromCurrent, other.itemsConsumedFromCurrent);
std::swap(currentProducer, other.currentProducer);
std::swap(desiredProducer, other.desiredProducer);
}
// Disable copying and assignment
ConsumerToken(ConsumerToken const&) = delete;
ConsumerToken& operator=(ConsumerToken const&) = delete;
private:
template<typename T, typename Traits> friend class ConcurrentQueue;
private: // but shared with ConcurrentQueue
std::uint32_t initialOffset;
std::uint32_t lastKnownGlobalOffset;
std::uint32_t itemsConsumedFromCurrent;
details::ConcurrentQueueProducerTypelessBase* currentProducer;
details::ConcurrentQueueProducerTypelessBase* desiredProducer;
};
template<typename T, typename Traits = ConcurrentQueueDefaultTraits>
class ConcurrentQueue
{
public:
struct ExplicitProducer;
typedef moodycamel::ProducerToken producer_token_t;
typedef moodycamel::ConsumerToken consumer_token_t;
typedef typename Traits::index_t index_t;
typedef typename Traits::size_t size_t;
static const size_t BLOCK_SIZE = static_cast<size_t>(Traits::BLOCK_SIZE);
static const size_t EXPLICIT_BLOCK_EMPTY_COUNTER_THRESHOLD = static_cast<size_t>(Traits::EXPLICIT_BLOCK_EMPTY_COUNTER_THRESHOLD);
static const size_t EXPLICIT_INITIAL_INDEX_SIZE = static_cast<size_t>(Traits::EXPLICIT_INITIAL_INDEX_SIZE);
static const std::uint32_t EXPLICIT_CONSUMER_CONSUMPTION_QUOTA_BEFORE_ROTATE = static_cast<std::uint32_t>(Traits::EXPLICIT_CONSUMER_CONSUMPTION_QUOTA_BEFORE_ROTATE);
#ifdef _MSC_VER
#pragma warning(push)
#pragma warning(disable: 4307) // + integral constant overflow (that's what the ternary expression is for!)
#pragma warning(disable: 4309) // static_cast: Truncation of constant value
#endif
static const size_t MAX_SUBQUEUE_SIZE = (details::const_numeric_max<size_t>::value - static_cast<size_t>(Traits::MAX_SUBQUEUE_SIZE) < BLOCK_SIZE) ? details::const_numeric_max<size_t>::value : ((static_cast<size_t>(Traits::MAX_SUBQUEUE_SIZE) + (BLOCK_SIZE - 1)) / BLOCK_SIZE * BLOCK_SIZE);
#ifdef _MSC_VER
#pragma warning(pop)
#endif
static_assert(!std::numeric_limits<size_t>::is_signed && std::is_integral<size_t>::value, "Traits::size_t must be an unsigned integral type");
static_assert(!std::numeric_limits<index_t>::is_signed && std::is_integral<index_t>::value, "Traits::index_t must be an unsigned integral type");
static_assert(sizeof(index_t) >= sizeof(size_t), "Traits::index_t must be at least as wide as Traits::size_t");
static_assert((BLOCK_SIZE > 1) && !(BLOCK_SIZE & (BLOCK_SIZE - 1)), "Traits::BLOCK_SIZE must be a power of 2 (and at least 2)");
static_assert((EXPLICIT_BLOCK_EMPTY_COUNTER_THRESHOLD > 1) && !(EXPLICIT_BLOCK_EMPTY_COUNTER_THRESHOLD & (EXPLICIT_BLOCK_EMPTY_COUNTER_THRESHOLD - 1)), "Traits::EXPLICIT_BLOCK_EMPTY_COUNTER_THRESHOLD must be a power of 2 (and greater than 1)");
static_assert((EXPLICIT_INITIAL_INDEX_SIZE > 1) && !(EXPLICIT_INITIAL_INDEX_SIZE & (EXPLICIT_INITIAL_INDEX_SIZE - 1)), "Traits::EXPLICIT_INITIAL_INDEX_SIZE must be a power of 2 (and greater than 1)");
public:
// Creates a queue with at least `capacity` element slots; note that the
// actual number of elements that can be inserted without additional memory
// allocation depends on the number of producers and the block size (e.g. if
// the block size is equal to `capacity`, only a single block will be allocated
// up-front, which means only a single producer will be able to enqueue elements
// without an extra allocation -- blocks aren't shared between producers).
// This method is not thread safe -- it is up to the user to ensure that the
// queue is fully constructed before it starts being used by other threads (this
// includes making the memory effects of construction visible, possibly with a
// memory barrier).
explicit ConcurrentQueue(size_t capacity = 6 * BLOCK_SIZE)
: producerListTail(nullptr),
producerCount(0),
initialBlockPoolIndex(0),
nextExplicitConsumerId(0),
globalExplicitConsumerOffset(0)
{
populate_initial_block_list(capacity / BLOCK_SIZE + ((capacity & (BLOCK_SIZE - 1)) == 0 ? 0 : 1));
}
// Computes the correct amount of pre-allocated blocks for you based
// on the minimum number of elements you want available at any given
// time, and the maximum concurrent number of each type of producer.
ConcurrentQueue(size_t minCapacity, size_t maxExplicitProducers)
: producerListTail(nullptr),
producerCount(0),
initialBlockPoolIndex(0),
nextExplicitConsumerId(0),
globalExplicitConsumerOffset(0)
{
size_t blocks = (((minCapacity + BLOCK_SIZE - 1) / BLOCK_SIZE) - 1) * (maxExplicitProducers + 1) + 2 * (maxExplicitProducers);
populate_initial_block_list(blocks);
}
// Note: The queue should not be accessed concurrently while it's
// being deleted. It's up to the user to synchronize this.
// This method is not thread safe.
~ConcurrentQueue()
{
// Destroy producers
auto ptr = producerListTail.load(std::memory_order_relaxed);
while (ptr != nullptr) {
auto next = ptr->next_prod();
if (ptr->token != nullptr) {
ptr->token->producer = nullptr;
}
destroy(ptr);
ptr = next;
}
// Destroy global free list
auto block = freeList.head_unsafe();
while (block != nullptr) {
auto next = block->freeListNext.load(std::memory_order_relaxed);
if (block->dynamicallyAllocated) {
destroy(block);
}
block = next;
}
// Destroy initial free list
destroy_array(initialBlockPool, initialBlockPoolSize);
}
// Disable copying and copy assignment
ConcurrentQueue(ConcurrentQueue const&) = delete;
ConcurrentQueue(ConcurrentQueue&& other) = delete;
ConcurrentQueue& operator=(ConcurrentQueue const&) = delete;
ConcurrentQueue& operator=(ConcurrentQueue&& other) = delete;
public:
tracy_force_inline T* enqueue_begin(producer_token_t const& token, index_t& currentTailIndex)
{
return static_cast<ExplicitProducer*>(token.producer)->ConcurrentQueue::ExplicitProducer::enqueue_begin(currentTailIndex);
}
template<class NotifyThread, class ProcessData>
size_t try_dequeue_bulk_single(consumer_token_t& token, NotifyThread notifyThread, ProcessData processData )
{
if (token.desiredProducer == nullptr || token.lastKnownGlobalOffset != globalExplicitConsumerOffset.load(std::memory_order_relaxed)) {
if (!update_current_producer_after_rotation(token)) {
return 0;
}
}
size_t count = static_cast<ProducerBase*>(token.currentProducer)->dequeue_bulk(notifyThread, processData);
token.itemsConsumedFromCurrent += static_cast<std::uint32_t>(count);
auto tail = producerListTail.load(std::memory_order_acquire);
auto ptr = static_cast<ProducerBase*>(token.currentProducer)->next_prod();
if (ptr == nullptr) {
ptr = tail;
}
if( count == 0 )
{
while (ptr != static_cast<ProducerBase*>(token.currentProducer)) {
auto dequeued = ptr->dequeue_bulk(notifyThread, processData);
if (dequeued != 0) {
token.currentProducer = ptr;
token.itemsConsumedFromCurrent = static_cast<std::uint32_t>(dequeued);
return dequeued;
}
ptr = ptr->next_prod();
if (ptr == nullptr) {
ptr = tail;
}
}
return 0;
}
else
{
token.currentProducer = ptr;
token.itemsConsumedFromCurrent = 0;
return count;
}
}
// Returns an estimate of the total number of elements currently in the queue. This
// estimate is only accurate if the queue has completely stabilized before it is called
// (i.e. all enqueue and dequeue operations have completed and their memory effects are
// visible on the calling thread, and no further operations start while this method is
// being called).
// Thread-safe.
size_t size_approx() const
{
size_t size = 0;
for (auto ptr = producerListTail.load(std::memory_order_acquire); ptr != nullptr; ptr = ptr->next_prod()) {
size += ptr->size_approx();
}
return size;
}
// Returns true if the underlying atomic variables used by
// the queue are lock-free (they should be on most platforms).
// Thread-safe.
static bool is_lock_free()
{
return
details::static_is_lock_free<bool>::value == 2 &&
details::static_is_lock_free<size_t>::value == 2 &&
details::static_is_lock_free<std::uint32_t>::value == 2 &&
details::static_is_lock_free<index_t>::value == 2 &&
details::static_is_lock_free<void*>::value == 2;
}
private:
friend struct ProducerToken;
friend struct ConsumerToken;
friend struct ExplicitProducer;
///////////////////////////////
// Queue methods
///////////////////////////////
inline bool update_current_producer_after_rotation(consumer_token_t& token)
{
// Ah, there's been a rotation, figure out where we should be!
auto tail = producerListTail.load(std::memory_order_acquire);
if (token.desiredProducer == nullptr && tail == nullptr) {
return false;
}
auto prodCount = producerCount.load(std::memory_order_relaxed);
auto globalOffset = globalExplicitConsumerOffset.load(std::memory_order_relaxed);
if (details::cqUnlikely(token.desiredProducer == nullptr)) {
// Aha, first time we're dequeueing anything.
// Figure out our local position
// Note: offset is from start, not end, but we're traversing from end -- subtract from count first
std::uint32_t offset = prodCount - 1 - (token.initialOffset % prodCount);
token.desiredProducer = tail;
for (std::uint32_t i = 0; i != offset; ++i) {
token.desiredProducer = static_cast<ProducerBase*>(token.desiredProducer)->next_prod();
if (token.desiredProducer == nullptr) {
token.desiredProducer = tail;
}
}
}
std::uint32_t delta = globalOffset - token.lastKnownGlobalOffset;
if (delta >= prodCount) {
delta = delta % prodCount;
}
for (std::uint32_t i = 0; i != delta; ++i) {
token.desiredProducer = static_cast<ProducerBase*>(token.desiredProducer)->next_prod();
if (token.desiredProducer == nullptr) {
token.desiredProducer = tail;
}
}
token.lastKnownGlobalOffset = globalOffset;
token.currentProducer = token.desiredProducer;
token.itemsConsumedFromCurrent = 0;
return true;
}
///////////////////////////
// Free list
///////////////////////////
template <typename N>
struct FreeListNode
{
FreeListNode() : freeListRefs(0), freeListNext(nullptr) { }
std::atomic<std::uint32_t> freeListRefs;
std::atomic<N*> freeListNext;
};
// A simple CAS-based lock-free free list. Not the fastest thing in the world under heavy contention, but
// simple and correct (assuming nodes are never freed until after the free list is destroyed), and fairly
// speedy under low contention.
template<typename N> // N must inherit FreeListNode or have the same fields (and initialization of them)
struct FreeList
{
FreeList() : freeListHead(nullptr) { }
FreeList(FreeList&& other) : freeListHead(other.freeListHead.load(std::memory_order_relaxed)) { other.freeListHead.store(nullptr, std::memory_order_relaxed); }
void swap(FreeList& other) { details::swap_relaxed(freeListHead, other.freeListHead); }
FreeList(FreeList const&) = delete;
FreeList& operator=(FreeList const&) = delete;
inline void add(N* node)
{
// We know that the should-be-on-freelist bit is 0 at this point, so it's safe to
// set it using a fetch_add
if (node->freeListRefs.fetch_add(SHOULD_BE_ON_FREELIST, std::memory_order_acq_rel) == 0) {
// Oh look! We were the last ones referencing this node, and we know
// we want to add it to the free list, so let's do it!
add_knowing_refcount_is_zero(node);
}
}
inline N* try_get()
{
auto head = freeListHead.load(std::memory_order_acquire);
while (head != nullptr) {
auto prevHead = head;
auto refs = head->freeListRefs.load(std::memory_order_relaxed);
if ((refs & REFS_MASK) == 0 || !head->freeListRefs.compare_exchange_strong(refs, refs + 1, std::memory_order_acquire, std::memory_order_relaxed)) {
head = freeListHead.load(std::memory_order_acquire);
continue;
}
// Good, reference count has been incremented (it wasn't at zero), which means we can read the
// next and not worry about it changing between now and the time we do the CAS
auto next = head->freeListNext.load(std::memory_order_relaxed);
if (freeListHead.compare_exchange_strong(head, next, std::memory_order_acquire, std::memory_order_relaxed)) {
// Yay, got the node. This means it was on the list, which means shouldBeOnFreeList must be false no
// matter the refcount (because nobody else knows it's been taken off yet, it can't have been put back on).
assert((head->freeListRefs.load(std::memory_order_relaxed) & SHOULD_BE_ON_FREELIST) == 0);
// Decrease refcount twice, once for our ref, and once for the list's ref
head->freeListRefs.fetch_sub(2, std::memory_order_release);
return head;
}
// OK, the head must have changed on us, but we still need to decrease the refcount we increased.
// Note that we don't need to release any memory effects, but we do need to ensure that the reference
// count decrement happens-after the CAS on the head.
refs = prevHead->freeListRefs.fetch_sub(1, std::memory_order_acq_rel);
if (refs == SHOULD_BE_ON_FREELIST + 1) {
add_knowing_refcount_is_zero(prevHead);
}
}
return nullptr;
}
// Useful for traversing the list when there's no contention (e.g. to destroy remaining nodes)
N* head_unsafe() const { return freeListHead.load(std::memory_order_relaxed); }
private:
inline void add_knowing_refcount_is_zero(N* node)
{
// Since the refcount is zero, and nobody can increase it once it's zero (except us, and we run
// only one copy of this method per node at a time, i.e. the single thread case), then we know
// we can safely change the next pointer of the node; however, once the refcount is back above
// zero, then other threads could increase it (happens under heavy contention, when the refcount
// goes to zero in between a load and a refcount increment of a node in try_get, then back up to
// something non-zero, then the refcount increment is done by the other thread) -- so, if the CAS
// to add the node to the actual list fails, decrease the refcount and leave the add operation to
// the next thread who puts the refcount back at zero (which could be us, hence the loop).
auto head = freeListHead.load(std::memory_order_relaxed);
while (true) {
node->freeListNext.store(head, std::memory_order_relaxed);
node->freeListRefs.store(1, std::memory_order_release);
if (!freeListHead.compare_exchange_strong(head, node, std::memory_order_release, std::memory_order_relaxed)) {
// Hmm, the add failed, but we can only try again when the refcount goes back to zero
if (node->freeListRefs.fetch_add(SHOULD_BE_ON_FREELIST - 1, std::memory_order_release) == 1) {
continue;
}
}
return;
}
}
private:
// Implemented like a stack, but where node order doesn't matter (nodes are inserted out of order under contention)
std::atomic<N*> freeListHead;
static const std::uint32_t REFS_MASK = 0x7FFFFFFF;
static const std::uint32_t SHOULD_BE_ON_FREELIST = 0x80000000;
};
///////////////////////////
// Block
///////////////////////////
struct Block
{
Block()
: next(nullptr), elementsCompletelyDequeued(0), freeListRefs(0), freeListNext(nullptr), shouldBeOnFreeList(false), dynamicallyAllocated(true)
{
}
inline bool is_empty() const
{
if (compile_time_condition<BLOCK_SIZE <= EXPLICIT_BLOCK_EMPTY_COUNTER_THRESHOLD>::value) {
// Check flags
for (size_t i = 0; i < BLOCK_SIZE; ++i) {
if (!emptyFlags[i].load(std::memory_order_relaxed)) {
return false;
}
}
// Aha, empty; make sure we have all other memory effects that happened before the empty flags were set
std::atomic_thread_fence(std::memory_order_acquire);
return true;
}
else {
// Check counter
if (elementsCompletelyDequeued.load(std::memory_order_relaxed) == BLOCK_SIZE) {
std::atomic_thread_fence(std::memory_order_acquire);
return true;
}
assert(elementsCompletelyDequeued.load(std::memory_order_relaxed) <= BLOCK_SIZE);
return false;
}
}
// Returns true if the block is now empty (does not apply in explicit context)
inline bool set_empty(index_t i)
{
if (BLOCK_SIZE <= EXPLICIT_BLOCK_EMPTY_COUNTER_THRESHOLD) {
// Set flag
assert(!emptyFlags[BLOCK_SIZE - 1 - static_cast<size_t>(i & static_cast<index_t>(BLOCK_SIZE - 1))].load(std::memory_order_relaxed));
emptyFlags[BLOCK_SIZE - 1 - static_cast<size_t>(i & static_cast<index_t>(BLOCK_SIZE - 1))].store(true, std::memory_order_release);
return false;
}
else {
// Increment counter
auto prevVal = elementsCompletelyDequeued.fetch_add(1, std::memory_order_release);
assert(prevVal < BLOCK_SIZE);
return prevVal == BLOCK_SIZE - 1;
}
}
// Sets multiple contiguous item statuses to 'empty' (assumes no wrapping and count > 0).
// Returns true if the block is now empty (does not apply in explicit context).
inline bool set_many_empty(index_t i, size_t count)
{
if (compile_time_condition<BLOCK_SIZE <= EXPLICIT_BLOCK_EMPTY_COUNTER_THRESHOLD>::value) {
// Set flags
std::atomic_thread_fence(std::memory_order_release);
i = BLOCK_SIZE - 1 - static_cast<size_t>(i & static_cast<index_t>(BLOCK_SIZE - 1)) - count + 1;
for (size_t j = 0; j != count; ++j) {
assert(!emptyFlags[i + j].load(std::memory_order_relaxed));
emptyFlags[i + j].store(true, std::memory_order_relaxed);
}
return false;
}
else {
// Increment counter
auto prevVal = elementsCompletelyDequeued.fetch_add(count, std::memory_order_release);
assert(prevVal + count <= BLOCK_SIZE);
return prevVal + count == BLOCK_SIZE;
}
}
inline void set_all_empty()
{
if (BLOCK_SIZE <= EXPLICIT_BLOCK_EMPTY_COUNTER_THRESHOLD) {
// Set all flags
for (size_t i = 0; i != BLOCK_SIZE; ++i) {
emptyFlags[i].store(true, std::memory_order_relaxed);
}
}
else {
// Reset counter
elementsCompletelyDequeued.store(BLOCK_SIZE, std::memory_order_relaxed);
}
}
inline void reset_empty()
{
if (compile_time_condition<BLOCK_SIZE <= EXPLICIT_BLOCK_EMPTY_COUNTER_THRESHOLD>::value) {
// Reset flags
for (size_t i = 0; i != BLOCK_SIZE; ++i) {
emptyFlags[i].store(false, std::memory_order_relaxed);
}
}
else {
// Reset counter
elementsCompletelyDequeued.store(0, std::memory_order_relaxed);
}
}
inline T* operator[](index_t idx) noexcept { return static_cast<T*>(static_cast<void*>(elements)) + static_cast<size_t>(idx & static_cast<index_t>(BLOCK_SIZE - 1)); }
inline T const* operator[](index_t idx) const noexcept { return static_cast<T const*>(static_cast<void const*>(elements)) + static_cast<size_t>(idx & static_cast<index_t>(BLOCK_SIZE - 1)); }
private:
// IMPORTANT: This must be the first member in Block, so that if T depends on the alignment of
// addresses returned by malloc, that alignment will be preserved. Apparently clang actually
// generates code that uses this assumption for AVX instructions in some cases. Ideally, we
// should also align Block to the alignment of T in case it's higher than malloc's 16-byte
// alignment, but this is hard to do in a cross-platform way. Assert for this case:
static_assert(std::alignment_of<T>::value <= std::alignment_of<details::max_align_t>::value, "The queue does not support super-aligned types at this time");
// Additionally, we need the alignment of Block itself to be a multiple of max_align_t since
// otherwise the appropriate padding will not be added at the end of Block in order to make
// arrays of Blocks all be properly aligned (not just the first one). We use a union to force
// this.
union {
char elements[sizeof(T) * BLOCK_SIZE];
details::max_align_t dummy;
};
public:
Block* next;
std::atomic<size_t> elementsCompletelyDequeued;
std::atomic<bool> emptyFlags[BLOCK_SIZE <= EXPLICIT_BLOCK_EMPTY_COUNTER_THRESHOLD ? BLOCK_SIZE : 1];
public:
std::atomic<std::uint32_t> freeListRefs;
std::atomic<Block*> freeListNext;
std::atomic<bool> shouldBeOnFreeList;
bool dynamicallyAllocated; // Perhaps a better name for this would be 'isNotPartOfInitialBlockPool'
};
static_assert(std::alignment_of<Block>::value >= std::alignment_of<details::max_align_t>::value, "Internal error: Blocks must be at least as aligned as the type they are wrapping");
///////////////////////////
// Producer base
///////////////////////////
struct ProducerBase : public details::ConcurrentQueueProducerTypelessBase
{
ProducerBase(ConcurrentQueue* parent_) :
tailIndex(0),
headIndex(0),
dequeueOptimisticCount(0),
dequeueOvercommit(0),
tailBlock(nullptr),
parent(parent_)
{
}
virtual ~ProducerBase() { };
template<class NotifyThread, class ProcessData>
inline size_t dequeue_bulk(NotifyThread notifyThread, ProcessData processData)
{
return static_cast<ExplicitProducer*>(this)->dequeue_bulk(notifyThread, processData);
}
inline ProducerBase* next_prod() const { return static_cast<ProducerBase*>(next); }
inline size_t size_approx() const
{
auto tail = tailIndex.load(std::memory_order_relaxed);
auto head = headIndex.load(std::memory_order_relaxed);
return details::circular_less_than(head, tail) ? static_cast<size_t>(tail - head) : 0;
}
inline index_t getTail() const { return tailIndex.load(std::memory_order_relaxed); }
protected:
std::atomic<index_t> tailIndex; // Where to enqueue to next
std::atomic<index_t> headIndex; // Where to dequeue from next
std::atomic<index_t> dequeueOptimisticCount;
std::atomic<index_t> dequeueOvercommit;
Block* tailBlock;
public:
ConcurrentQueue* parent;
};
public:
///////////////////////////
// Explicit queue
///////////////////////////
struct ExplicitProducer : public ProducerBase
{
explicit ExplicitProducer(ConcurrentQueue* _parent) :
ProducerBase(_parent),
blockIndex(nullptr),
pr_blockIndexSlotsUsed(0),
pr_blockIndexSize(EXPLICIT_INITIAL_INDEX_SIZE >> 1),
pr_blockIndexFront(0),
pr_blockIndexEntries(nullptr),
pr_blockIndexRaw(nullptr)
{
size_t poolBasedIndexSize = details::ceil_to_pow_2(_parent->initialBlockPoolSize) >> 1;
if (poolBasedIndexSize > pr_blockIndexSize) {
pr_blockIndexSize = poolBasedIndexSize;
}
new_block_index(0); // This creates an index with double the number of current entries, i.e. EXPLICIT_INITIAL_INDEX_SIZE
}
~ExplicitProducer()
{
// Destruct any elements not yet dequeued.
// Since we're in the destructor, we can assume all elements
// are either completely dequeued or completely not (no halfways).
if (this->tailBlock != nullptr) { // Note this means there must be a block index too
// First find the block that's partially dequeued, if any
Block* halfDequeuedBlock = nullptr;
if ((this->headIndex.load(std::memory_order_relaxed) & static_cast<index_t>(BLOCK_SIZE - 1)) != 0) {
// The head's not on a block boundary, meaning a block somewhere is partially dequeued
// (or the head block is the tail block and was fully dequeued, but the head/tail are still not on a boundary)
size_t i = (pr_blockIndexFront - pr_blockIndexSlotsUsed) & (pr_blockIndexSize - 1);
while (details::circular_less_than<index_t>(pr_blockIndexEntries[i].base + BLOCK_SIZE, this->headIndex.load(std::memory_order_relaxed))) {
i = (i + 1) & (pr_blockIndexSize - 1);
}
assert(details::circular_less_than<index_t>(pr_blockIndexEntries[i].base, this->headIndex.load(std::memory_order_relaxed)));
halfDequeuedBlock = pr_blockIndexEntries[i].block;
}
// Start at the head block (note the first line in the loop gives us the head from the tail on the first iteration)
auto block = this->tailBlock;
do {
block = block->next;
if (block->ConcurrentQueue::Block::is_empty()) {
continue;
}
size_t i = 0; // Offset into block
if (block == halfDequeuedBlock) {
i = static_cast<size_t>(this->headIndex.load(std::memory_order_relaxed) & static_cast<index_t>(BLOCK_SIZE - 1));
}
// Walk through all the items in the block; if this is the tail block, we need to stop when we reach the tail index
auto lastValidIndex = (this->tailIndex.load(std::memory_order_relaxed) & static_cast<index_t>(BLOCK_SIZE - 1)) == 0 ? BLOCK_SIZE : static_cast<size_t>(this->tailIndex.load(std::memory_order_relaxed) & static_cast<index_t>(BLOCK_SIZE - 1));
while (i != BLOCK_SIZE && (block != this->tailBlock || i != lastValidIndex)) {
(*block)[i++]->~T();
}
} while (block != this->tailBlock);
}
// Destroy all blocks that we own
if (this->tailBlock != nullptr) {
auto block = this->tailBlock;
do {
auto nextBlock = block->next;
if (block->dynamicallyAllocated) {
destroy(block);
}
else {
this->parent->add_block_to_free_list(block);
}
block = nextBlock;
} while (block != this->tailBlock);
}
// Destroy the block indices
auto header = static_cast<BlockIndexHeader*>(pr_blockIndexRaw);
while (header != nullptr) {
auto prev = static_cast<BlockIndexHeader*>(header->prev);
header->~BlockIndexHeader();
(Traits::free)(header);
header = prev;
}
}
inline void enqueue_begin_alloc(index_t currentTailIndex)
{
// We reached the end of a block, start a new one
if (this->tailBlock != nullptr && this->tailBlock->next->ConcurrentQueue::Block::is_empty()) {
// We can re-use the block ahead of us, it's empty!
this->tailBlock = this->tailBlock->next;
this->tailBlock->ConcurrentQueue::Block::reset_empty();
// We'll put the block on the block index (guaranteed to be room since we're conceptually removing the
// last block from it first -- except instead of removing then adding, we can just overwrite).
// Note that there must be a valid block index here, since even if allocation failed in the ctor,
// it would have been re-attempted when adding the first block to the queue; since there is such
// a block, a block index must have been successfully allocated.
}
else {
// We're going to need a new block; check that the block index has room
if (pr_blockIndexRaw == nullptr || pr_blockIndexSlotsUsed == pr_blockIndexSize) {
// Hmm, the circular block index is already full -- we'll need
// to allocate a new index. Note pr_blockIndexRaw can only be nullptr if
// the initial allocation failed in the constructor.
new_block_index(pr_blockIndexSlotsUsed);
}
// Insert a new block in the circular linked list
auto newBlock = this->parent->ConcurrentQueue::requisition_block();
newBlock->ConcurrentQueue::Block::reset_empty();
if (this->tailBlock == nullptr) {
newBlock->next = newBlock;
}
else {
newBlock->next = this->tailBlock->next;
this->tailBlock->next = newBlock;
}
this->tailBlock = newBlock;
++pr_blockIndexSlotsUsed;
}
// Add block to block index
auto& entry = blockIndex.load(std::memory_order_relaxed)->entries[pr_blockIndexFront];
entry.base = currentTailIndex;
entry.block = this->tailBlock;
blockIndex.load(std::memory_order_relaxed)->front.store(pr_blockIndexFront, std::memory_order_release);
pr_blockIndexFront = (pr_blockIndexFront + 1) & (pr_blockIndexSize - 1);
}
tracy_force_inline T* enqueue_begin(index_t& currentTailIndex)
{
currentTailIndex = this->tailIndex.load(std::memory_order_relaxed);
if (details::cqUnlikely((currentTailIndex & static_cast<index_t>(BLOCK_SIZE - 1)) == 0)) {
this->enqueue_begin_alloc(currentTailIndex);
}
return (*this->tailBlock)[currentTailIndex];
}
tracy_force_inline std::atomic<index_t>& get_tail_index()
{
return this->tailIndex;
}
template<class NotifyThread, class ProcessData>
size_t dequeue_bulk(NotifyThread notifyThread, ProcessData processData)
{
auto tail = this->tailIndex.load(std::memory_order_relaxed);
auto overcommit = this->dequeueOvercommit.load(std::memory_order_relaxed);
auto desiredCount = static_cast<size_t>(tail - (this->dequeueOptimisticCount.load(std::memory_order_relaxed) - overcommit));
if (details::circular_less_than<size_t>(0, desiredCount)) {
desiredCount = desiredCount < 8192 ? desiredCount : 8192;
std::atomic_thread_fence(std::memory_order_acquire);
auto myDequeueCount = this->dequeueOptimisticCount.fetch_add(desiredCount, std::memory_order_relaxed);
assert(overcommit <= myDequeueCount);
tail = this->tailIndex.load(std::memory_order_acquire);
auto actualCount = static_cast<size_t>(tail - (myDequeueCount - overcommit));
if (details::circular_less_than<size_t>(0, actualCount)) {
actualCount = desiredCount < actualCount ? desiredCount : actualCount;
if (actualCount < desiredCount) {
this->dequeueOvercommit.fetch_add(desiredCount - actualCount, std::memory_order_release);
}
// Get the first index. Note that since there's guaranteed to be at least actualCount elements, this
// will never exceed tail.
auto firstIndex = this->headIndex.fetch_add(actualCount, std::memory_order_acq_rel);
// Determine which block the first element is in
auto localBlockIndex = blockIndex.load(std::memory_order_acquire);
auto localBlockIndexHead = localBlockIndex->front.load(std::memory_order_acquire);
auto headBase = localBlockIndex->entries[localBlockIndexHead].base;
auto firstBlockBaseIndex = firstIndex & ~static_cast<index_t>(BLOCK_SIZE - 1);
auto offset = static_cast<size_t>(static_cast<typename std::make_signed<index_t>::type>(firstBlockBaseIndex - headBase) / BLOCK_SIZE);
auto indexIndex = (localBlockIndexHead + offset) & (localBlockIndex->size - 1);
notifyThread( this->threadId );
// Iterate the blocks and dequeue
auto index = firstIndex;
do {
auto firstIndexInBlock = index;
auto endIndex = (index & ~static_cast<index_t>(BLOCK_SIZE - 1)) + static_cast<index_t>(BLOCK_SIZE);
endIndex = details::circular_less_than<index_t>(firstIndex + static_cast<index_t>(actualCount), endIndex) ? firstIndex + static_cast<index_t>(actualCount) : endIndex;
auto block = localBlockIndex->entries[indexIndex].block;
const auto sz = endIndex - index;
processData( (*block)[index], sz );
index += sz;
block->ConcurrentQueue::Block::set_many_empty(firstIndexInBlock, static_cast<size_t>(endIndex - firstIndexInBlock));
indexIndex = (indexIndex + 1) & (localBlockIndex->size - 1);
} while (index != firstIndex + actualCount);
return actualCount;
}
else {
// Wasn't anything to dequeue after all; make the effective dequeue count eventually consistent
this->dequeueOvercommit.fetch_add(desiredCount, std::memory_order_release);
}
}
return 0;
}
private:
struct BlockIndexEntry
{
index_t base;
Block* block;
};
struct BlockIndexHeader
{
size_t size;
std::atomic<size_t> front; // Current slot (not next, like pr_blockIndexFront)
BlockIndexEntry* entries;
void* prev;
};
bool new_block_index(size_t numberOfFilledSlotsToExpose)
{
auto prevBlockSizeMask = pr_blockIndexSize - 1;
// Create the new block
pr_blockIndexSize <<= 1;
auto newRawPtr = static_cast<char*>((Traits::malloc)(sizeof(BlockIndexHeader) + std::alignment_of<BlockIndexEntry>::value - 1 + sizeof(BlockIndexEntry) * pr_blockIndexSize));
if (newRawPtr == nullptr) {
pr_blockIndexSize >>= 1; // Reset to allow graceful retry
return false;
}
auto newBlockIndexEntries = reinterpret_cast<BlockIndexEntry*>(details::align_for<BlockIndexEntry>(newRawPtr + sizeof(BlockIndexHeader)));
// Copy in all the old indices, if any
size_t j = 0;
if (pr_blockIndexSlotsUsed != 0) {
auto i = (pr_blockIndexFront - pr_blockIndexSlotsUsed) & prevBlockSizeMask;
do {
newBlockIndexEntries[j++] = pr_blockIndexEntries[i];
i = (i + 1) & prevBlockSizeMask;
} while (i != pr_blockIndexFront);
}
// Update everything
auto header = new (newRawPtr) BlockIndexHeader;
header->size = pr_blockIndexSize;
header->front.store(numberOfFilledSlotsToExpose - 1, std::memory_order_relaxed);
header->entries = newBlockIndexEntries;
header->prev = pr_blockIndexRaw; // we link the new block to the old one so we can free it later
pr_blockIndexFront = j;
pr_blockIndexEntries = newBlockIndexEntries;
pr_blockIndexRaw = newRawPtr;
blockIndex.store(header, std::memory_order_release);
return true;
}
private:
std::atomic<BlockIndexHeader*> blockIndex;
// To be used by producer only -- consumer must use the ones in referenced by blockIndex
size_t pr_blockIndexSlotsUsed;
size_t pr_blockIndexSize;
size_t pr_blockIndexFront; // Next slot (not current)
BlockIndexEntry* pr_blockIndexEntries;
void* pr_blockIndexRaw;
};
ExplicitProducer* get_explicit_producer(producer_token_t const& token)
{
return static_cast<ExplicitProducer*>(token.producer);
}
private:
//////////////////////////////////
// Block pool manipulation
//////////////////////////////////
void populate_initial_block_list(size_t blockCount)
{
initialBlockPoolSize = blockCount;
if (initialBlockPoolSize == 0) {
initialBlockPool = nullptr;
return;
}
initialBlockPool = create_array<Block>(blockCount);
if (initialBlockPool == nullptr) {
initialBlockPoolSize = 0;
}
for (size_t i = 0; i < initialBlockPoolSize; ++i) {
initialBlockPool[i].dynamicallyAllocated = false;
}
}
inline Block* try_get_block_from_initial_pool()
{
if (initialBlockPoolIndex.load(std::memory_order_relaxed) >= initialBlockPoolSize) {
return nullptr;
}
auto index = initialBlockPoolIndex.fetch_add(1, std::memory_order_relaxed);
return index < initialBlockPoolSize ? (initialBlockPool + index) : nullptr;
}
inline void add_block_to_free_list(Block* block)
{
freeList.add(block);
}
inline void add_blocks_to_free_list(Block* block)
{
while (block != nullptr) {
auto next = block->next;
add_block_to_free_list(block);
block = next;
}
}
inline Block* try_get_block_from_free_list()
{
return freeList.try_get();
}
// Gets a free block from one of the memory pools, or allocates a new one (if applicable)
Block* requisition_block()
{
auto block = try_get_block_from_initial_pool();
if (block != nullptr) {
return block;
}
block = try_get_block_from_free_list();
if (block != nullptr) {
return block;
}
return create<Block>();
}
//////////////////////////////////
// Producer list manipulation
//////////////////////////////////
ProducerBase* recycle_or_create_producer()
{
bool recycled;
return recycle_or_create_producer(recycled);
}
ProducerBase* recycle_or_create_producer(bool& recycled)
{
// Try to re-use one first
for (auto ptr = producerListTail.load(std::memory_order_acquire); ptr != nullptr; ptr = ptr->next_prod()) {
if (ptr->inactive.load(std::memory_order_relaxed)) {
if( ptr->size_approx() == 0 )
{
bool expected = true;
if (ptr->inactive.compare_exchange_strong(expected, /* desired */ false, std::memory_order_acquire, std::memory_order_relaxed)) {
// We caught one! It's been marked as activated, the caller can have it
recycled = true;
return ptr;
}
}
}
}
recycled = false;
return add_producer(static_cast<ProducerBase*>(create<ExplicitProducer>(this)));
}
ProducerBase* add_producer(ProducerBase* producer)
{
// Handle failed memory allocation
if (producer == nullptr) {
return nullptr;
}
producerCount.fetch_add(1, std::memory_order_relaxed);
// Add it to the lock-free list
auto prevTail = producerListTail.load(std::memory_order_relaxed);
do {
producer->next = prevTail;
} while (!producerListTail.compare_exchange_weak(prevTail, producer, std::memory_order_release, std::memory_order_relaxed));
return producer;
}
void reown_producers()
{
// After another instance is moved-into/swapped-with this one, all the
// producers we stole still think their parents are the other queue.
// So fix them up!
for (auto ptr = producerListTail.load(std::memory_order_relaxed); ptr != nullptr; ptr = ptr->next_prod()) {
ptr->parent = this;
}
}
//////////////////////////////////
// Utility functions
//////////////////////////////////
template<typename U>
static inline U* create_array(size_t count)
{
assert(count > 0);
return static_cast<U*>((Traits::malloc)(sizeof(U) * count));
}
template<typename U>
static inline void destroy_array(U* p, size_t count)
{
((void)count);
if (p != nullptr) {
assert(count > 0);
(Traits::free)(p);
}
}
template<typename U>
static inline U* create()
{
auto p = (Traits::malloc)(sizeof(U));
return new (p) U;
}
template<typename U, typename A1>
static inline U* create(A1&& a1)
{
auto p = (Traits::malloc)(sizeof(U));
return new (p) U(std::forward<A1>(a1));
}
template<typename U>
static inline void destroy(U* p)
{
if (p != nullptr) {
p->~U();
}
(Traits::free)(p);
}
private:
std::atomic<ProducerBase*> producerListTail;
std::atomic<std::uint32_t> producerCount;
std::atomic<size_t> initialBlockPoolIndex;
Block* initialBlockPool;
size_t initialBlockPoolSize;
FreeList<Block> freeList;
std::atomic<std::uint32_t> nextExplicitConsumerId;
std::atomic<std::uint32_t> globalExplicitConsumerOffset;
};
template<typename T, typename Traits>
ProducerToken::ProducerToken(ConcurrentQueue<T, Traits>& queue)
: producer(queue.recycle_or_create_producer())
{
if (producer != nullptr) {
producer->token = this;
producer->threadId = detail::GetThreadHandleImpl();
}
}
template<typename T, typename Traits>
ConsumerToken::ConsumerToken(ConcurrentQueue<T, Traits>& queue)
: itemsConsumedFromCurrent(0), currentProducer(nullptr), desiredProducer(nullptr)
{
initialOffset = queue.nextExplicitConsumerId.fetch_add(1, std::memory_order_release);
lastKnownGlobalOffset = static_cast<std::uint32_t>(-1);
}
template<typename T, typename Traits>
inline void swap(ConcurrentQueue<T, Traits>& a, ConcurrentQueue<T, Traits>& b) noexcept
{
a.swap(b);
}
inline void swap(ProducerToken& a, ProducerToken& b) noexcept
{
a.swap(b);
}
inline void swap(ConsumerToken& a, ConsumerToken& b) noexcept
{
a.swap(b);
}
}
} /* namespace tracy */
#if defined(__GNUC__)
#pragma GCC diagnostic pop
#endif