Actual source code: segmentedmempool.hpp
1: #ifndef PETSC_SEGMENTEDMEMPOOL_HPP
2: #define PETSC_SEGMENTEDMEMPOOL_HPP
4: #include <petsc/private/deviceimpl.h>
6: #include <petsc/private/cpp/macros.hpp>
7: #include <petsc/private/cpp/type_traits.hpp>
8: #include <petsc/private/cpp/utility.hpp>
9: #include <petsc/private/cpp/register_finalize.hpp>
10: #include <petsc/private/cpp/memory.hpp>
12: #include <limits>
13: #include <deque>
14: #include <vector>
16: namespace Petsc
17: {
19: namespace device
20: {
22: template <typename T>
23: class StreamBase {
24: public:
25: using id_type = int;
26: using derived_type = T;
28: static const id_type INVALID_ID;
30: // needed so that dependent auto works, see veccupmimpl.h for a detailed discussion
31: template <typename U = T>
32: PETSC_NODISCARD auto get_stream() const noexcept PETSC_DECLTYPE_AUTO_RETURNS(static_cast<const U &>(*this).get_stream_());
34: PETSC_NODISCARD id_type get_id() const noexcept { return static_cast<const T &>(*this).get_id_(); }
36: template <typename E>
37: PetscErrorCode record_event(E &&event) const noexcept
38: {
39: return static_cast<const T &>(*this).record_event_(std::forward<E>(event));
40: }
42: template <typename E>
43: PetscErrorCode wait_for_event(E &&event) const noexcept
44: {
45: return static_cast<const T &>(*this).wait_for_(std::forward<E>(event));
46: }
48: protected:
49: constexpr StreamBase() noexcept = default;
51: struct default_event_type { };
52: using default_stream_type = std::nullptr_t;
54: PETSC_NODISCARD static constexpr default_stream_type get_stream_() noexcept { return nullptr; }
56: PETSC_NODISCARD static constexpr id_type get_id_() noexcept { return 0; }
58: template <typename U = T>
59: static constexpr PetscErrorCode record_event_(const typename U::event_type &) noexcept
60: {
61: return PETSC_SUCCESS;
62: }
64: template <typename U = T>
65: static constexpr PetscErrorCode wait_for_(const typename U::event_type &) noexcept
66: {
67: return PETSC_SUCCESS;
68: }
69: };
71: template <typename T>
72: const typename StreamBase<T>::id_type StreamBase<T>::INVALID_ID = -1;
74: struct DefaultStream : StreamBase<DefaultStream> {
75: using stream_type = typename StreamBase<DefaultStream>::default_stream_type;
76: using id_type = typename StreamBase<DefaultStream>::id_type;
77: using event_type = typename StreamBase<DefaultStream>::default_event_type;
78: };
80: } // namespace device
82: namespace memory
83: {
85: namespace impl
86: {
88: // ==========================================================================================
89: // MemoryChunk
90: //
91: // Represents a checked-out region of a MemoryBlock. Tracks the offset into the owning
92: // MemoryBlock and its size/capacity
93: // ==========================================================================================
95: template <typename EventType>
96: class MemoryChunk {
97: public:
98: using event_type = EventType;
99: using size_type = std::size_t;
101: MemoryChunk(size_type, size_type) noexcept;
102: explicit MemoryChunk(size_type) noexcept;
104: MemoryChunk(MemoryChunk &&) noexcept;
105: MemoryChunk &operator=(MemoryChunk &&) noexcept;
107: MemoryChunk(const MemoryChunk &) noexcept = delete;
108: MemoryChunk &operator=(const MemoryChunk &) noexcept = delete;
110: PETSC_NODISCARD size_type start() const noexcept { return start_; }
111: PETSC_NODISCARD size_type size() const noexcept { return size_; }
112: // REVIEW ME:
113: // make this an actual field, normally each chunk shrinks_to_fit() on begin claimed, but in
114: // theory only the last chunk needs to do this
115: PETSC_NODISCARD size_type capacity() const noexcept { return size_; }
116: PETSC_NODISCARD size_type total_offset() const noexcept { return start() + size(); }
118: template <typename U>
119: PetscErrorCode release(const device::StreamBase<U> *) noexcept;
120: template <typename U>
121: PetscErrorCode claim(const device::StreamBase<U> *, size_type, bool *, bool = false) noexcept;
122: template <typename U>
123: PETSC_NODISCARD bool can_claim(const device::StreamBase<U> *, size_type, bool) const noexcept;
124: PetscErrorCode resize(size_type) noexcept;
125: PETSC_NODISCARD bool contains(size_type) const noexcept;
127: private:
128: // clang-format off
129: event_type event_{}; // event recorded when the chunk was released
130: bool open_ = true; // is this chunk open?
131: // id of the last stream to use the chunk, populated on release
132: int stream_id_ = device::DefaultStream::INVALID_ID;
133: size_type size_ = 0; // size of the chunk
134: const size_type start_ = 0; // offset from the start of the owning block
135: // clang-format on
137: template <typename U>
138: PETSC_NODISCARD bool stream_compat_(const device::StreamBase<U> *) const noexcept;
139: };
141: // ==========================================================================================
142: // MemoryChunk - Private API
143: // ==========================================================================================
145: // asks and answers the question: can this stream claim this chunk without serializing?
146: template <typename E>
147: template <typename U>
148: inline bool MemoryChunk<E>::stream_compat_(const device::StreamBase<U> *strm) const noexcept
149: {
150: return (stream_id_ == strm->INVALID_ID) || (stream_id_ == strm->get_id());
151: }
153: // ==========================================================================================
154: // MemoryChunk - Public API
155: // ==========================================================================================
157: template <typename E>
158: inline MemoryChunk<E>::MemoryChunk(size_type start, size_type size) noexcept : size_(size), start_(start)
159: {
160: }
162: template <typename E>
163: inline MemoryChunk<E>::MemoryChunk(size_type size) noexcept : MemoryChunk(0, size)
164: {
165: }
167: template <typename E>
168: inline MemoryChunk<E>::MemoryChunk(MemoryChunk<E> &&other) noexcept :
169: event_(std::move(other.event_)), open_(util::exchange(other.open_, false)), stream_id_(util::exchange(other.stream_id_, device::DefaultStream::INVALID_ID)), size_(util::exchange(other.size_, 0)), start_(std::move(other.start_))
170: {
171: }
173: template <typename E>
174: inline MemoryChunk<E> &MemoryChunk<E>::operator=(MemoryChunk<E> &&other) noexcept
175: {
176: PetscFunctionBegin;
177: if (this != &other) {
178: event_ = std::move(other.event_);
179: open_ = util::exchange(other.open_, false);
180: stream_id_ = util::exchange(other.stream_id_, device::DefaultStream::INVALID_ID);
181: size_ = util::exchange(other.size_, 0);
182: start_ = std::move(other.start_);
183: }
184: PetscFunctionReturn(*this);
185: }
187: /*
188: MemoryChunk::release - release a chunk on a stream
190: Input Parameter:
191: . stream - the stream to release the chunk with
193: Notes:
194: Inserts a release operation on stream and records the state of stream at the time this
195: routine was called.
197: Future allocation requests which attempt to claim the chunk on the same stream may re-acquire
198: the chunk without serialization.
200: If another stream attempts to claim the chunk they must wait for the recorded event before
201: claiming the chunk.
202: */
203: template <typename E>
204: template <typename U>
205: inline PetscErrorCode MemoryChunk<E>::release(const device::StreamBase<U> *stream) noexcept
206: {
207: PetscFunctionBegin;
208: open_ = true;
209: stream_id_ = stream->get_id();
210: PetscCall(stream->record_event(event_));
211: PetscFunctionReturn(PETSC_SUCCESS);
212: }
214: /*
215: MemoryChunk::claim - attempt to claim a particular chunk
217: Input Parameters:
218: + stream - the stream on which to attempt to claim
219: . req_size - the requested size (in elements) to attempt to claim
220: - serialize - (optional, false) whether the claimant allows serialization
222: Output Parameter:
223: . success - true if the chunk was claimed, false otherwise
224: */
225: template <typename E>
226: template <typename U>
227: inline PetscErrorCode MemoryChunk<E>::claim(const device::StreamBase<U> *stream, size_type req_size, bool *success, bool serialize) noexcept
228: {
229: PetscFunctionBegin;
230: if ((*success = can_claim(stream, req_size, serialize))) {
231: if (serialize && !stream_compat_(stream)) PetscCall(stream->wait_for_event(event_));
232: PetscCall(resize(req_size));
233: open_ = false;
234: }
235: PetscFunctionReturn(PETSC_SUCCESS);
236: }
238: /*
239: MemoryChunk::can_claim - test whether a particular chunk can be claimed
241: Input Parameters:
242: + stream - the stream on which to attempt to claim
243: . req_size - the requested size (in elements) to attempt to claim
244: - serialize - whether the claimant allows serialization
246: Output:
247: . [return] - true if the chunk is claimable given the configuration, false otherwise
248: */
249: template <typename E>
250: template <typename U>
251: inline bool MemoryChunk<E>::can_claim(const device::StreamBase<U> *stream, size_type req_size, bool serialize) const noexcept
252: {
253: if (open_ && (req_size <= capacity())) {
254: // fully compatible
255: if (stream_compat_(stream)) return true;
256: // stream wasn't compatible, but could claim if we serialized
257: if (serialize) return true;
258: // incompatible stream and did not want to serialize
259: }
260: return false;
261: }
263: /*
264: MemoryChunk::resize - grow a chunk to new size
266: Input Parameter:
267: . newsize - the new size Requested
269: Notes:
270: newsize cannot be larger than capacity
271: */
272: template <typename E>
273: inline PetscErrorCode MemoryChunk<E>::resize(size_type newsize) noexcept
274: {
275: PetscFunctionBegin;
276: PetscAssert(newsize <= capacity(), PETSC_COMM_SELF, PETSC_ERR_ARG_SIZ, "New size %zu larger than capacity %zu", newsize, capacity());
277: size_ = newsize;
278: PetscFunctionReturn(PETSC_SUCCESS);
279: }
281: /*
282: MemoryChunk::contains - query whether a memory chunk contains a particular offset
284: Input Parameters:
285: . offset - The offset from the MemoryBlock start
287: Notes:
288: Returns true if the chunk contains the offset, false otherwise
289: */
290: template <typename E>
291: inline bool MemoryChunk<E>::contains(size_type offset) const noexcept
292: {
293: return (offset >= start()) && (offset < total_offset());
294: }
296: // ==========================================================================================
297: // MemoryBlock
298: //
299: // A "memory block" manager, which owns the pointer to a particular memory range. Retrieving
300: // and restoring a block is thread-safe (so may be used by multiple device streams).
301: // ==========================================================================================
303: template <typename T, typename AllocatorType, typename StreamType>
304: class MemoryBlock {
305: public:
306: using value_type = T;
307: using allocator_type = AllocatorType;
308: using stream_type = StreamType;
309: using event_type = typename stream_type::event_type;
310: using chunk_type = MemoryChunk<event_type>;
311: using size_type = typename chunk_type::size_type;
312: using chunk_list_type = std::vector<chunk_type>;
314: template <typename U>
315: MemoryBlock(allocator_type *, size_type, const device::StreamBase<U> *) noexcept;
317: ~MemoryBlock() noexcept(std::is_nothrow_destructible<chunk_list_type>::value);
319: MemoryBlock(MemoryBlock &&) noexcept;
320: MemoryBlock &operator=(MemoryBlock &&) noexcept;
322: // memory blocks are not copyable
323: MemoryBlock(const MemoryBlock &) = delete;
324: MemoryBlock &operator=(const MemoryBlock &) = delete;
326: /* --- actual functions --- */
327: PetscErrorCode try_allocate_chunk(size_type, T **, const stream_type *, bool *) noexcept;
328: PetscErrorCode try_deallocate_chunk(T **, const stream_type *, bool *) noexcept;
329: PetscErrorCode try_find_chunk(const T *, chunk_type **) noexcept;
330: PETSC_NODISCARD bool owns_pointer(const T *) const noexcept;
332: PETSC_NODISCARD size_type size() const noexcept { return size_; }
333: PETSC_NODISCARD size_type bytes() const noexcept { return sizeof(value_type) * size(); }
334: PETSC_NODISCARD size_type num_chunks() const noexcept { return chunks_.size(); }
336: private:
337: value_type *mem_{};
338: allocator_type *allocator_{};
339: size_type size_{};
340: chunk_list_type chunks_{};
342: PetscErrorCode clear_(const stream_type *) noexcept;
343: };
345: // ==========================================================================================
346: // MemoryBlock - Private API
347: // ==========================================================================================
349: // clear the memory block, called from destructors and move assignment/construction
350: template <typename T, typename A, typename S>
351: PetscErrorCode MemoryBlock<T, A, S>::clear_(const stream_type *stream) noexcept
352: {
353: PetscFunctionBegin;
354: if (PetscLikely(mem_)) {
355: PetscCall(allocator_->deallocate(mem_, stream));
356: mem_ = nullptr;
357: }
358: size_ = 0;
359: PetscCallCXX(chunks_.clear());
360: PetscFunctionReturn(PETSC_SUCCESS);
361: }
363: // ==========================================================================================
364: // MemoryBlock - Public API
365: // ==========================================================================================
367: // default constructor, allocates memory immediately
368: template <typename T, typename A, typename S>
369: template <typename U>
370: MemoryBlock<T, A, S>::MemoryBlock(allocator_type *alloc, size_type s, const device::StreamBase<U> *stream) noexcept : allocator_(alloc), size_(s)
371: {
372: PetscFunctionBegin;
373: PetscCallAbort(PETSC_COMM_SELF, alloc->allocate(&mem_, s, stream));
374: PetscAssertAbort(mem_, PETSC_COMM_SELF, PETSC_ERR_MEM, "Failed to allocate memory block of size %zu", s);
375: PetscFunctionReturnVoid();
376: }
378: template <typename T, typename A, typename S>
379: MemoryBlock<T, A, S>::~MemoryBlock() noexcept(std::is_nothrow_destructible<chunk_list_type>::value)
380: {
381: stream_type stream;
383: PetscFunctionBegin;
384: PetscCallAbort(PETSC_COMM_SELF, clear_(&stream));
385: PetscFunctionReturnVoid();
386: }
388: template <typename T, typename A, typename S>
389: MemoryBlock<T, A, S>::MemoryBlock(MemoryBlock &&other) noexcept : mem_(util::exchange(other.mem_, nullptr)), allocator_(other.allocator_), size_(util::exchange(other.size_, 0)), chunks_(std::move(other.chunks_))
390: {
391: }
393: template <typename T, typename A, typename S>
394: MemoryBlock<T, A, S> &MemoryBlock<T, A, S>::operator=(MemoryBlock &&other) noexcept
395: {
396: PetscFunctionBegin;
397: if (this != &other) {
398: stream_type stream;
400: PetscCallAbort(PETSC_COMM_SELF, clear_(&stream));
401: mem_ = util::exchange(other.mem_, nullptr);
402: allocator_ = other.allocator_;
403: size_ = util::exchange(other.size_, 0);
404: chunks_ = std::move(other.chunks_);
405: }
406: PetscFunctionReturn(*this);
407: }
409: /*
410: MemoryBock::owns_pointer - returns true if this block owns a pointer, false otherwise
411: */
412: template <typename T, typename A, typename S>
413: inline bool MemoryBlock<T, A, S>::owns_pointer(const T *ptr) const noexcept
414: {
415: // each pool is linear in memory, so it suffices to check the bounds
416: return (ptr >= mem_) && (ptr < std::next(mem_, size()));
417: }
419: /*
420: MemoryBlock::try_allocate_chunk - try to get a chunk from this MemoryBlock
422: Input Parameters:
423: + req_size - the requested size of the allocation (in elements)
424: . ptr - ptr to fill
425: - stream - stream to fill the pointer on
427: Output Parameter:
428: . success - true if chunk was gotten, false otherwise
430: Notes:
431: If the current memory could not satisfy the memory request, ptr is unchanged
432: */
433: template <typename T, typename A, typename S>
434: inline PetscErrorCode MemoryBlock<T, A, S>::try_allocate_chunk(size_type req_size, T **ptr, const stream_type *stream, bool *success) noexcept
435: {
436: PetscFunctionBegin;
437: *success = false;
438: if (req_size <= size()) {
439: const auto try_create_chunk = [&]() {
440: const auto was_empty = chunks_.empty();
441: const auto block_alloced = was_empty ? 0 : chunks_.back().total_offset();
443: PetscFunctionBegin;
444: if (block_alloced + req_size <= size()) {
445: PetscCallCXX(chunks_.emplace_back(block_alloced, req_size));
446: PetscCall(chunks_.back().claim(stream, req_size, success));
447: *ptr = mem_ + block_alloced;
448: if (was_empty) PetscAssert(*success, PETSC_COMM_SELF, PETSC_ERR_PLIB, "Failed to claim chunk (of size %zu) even though block (of size %zu) was empty!", req_size, size());
449: }
450: PetscFunctionReturn(PETSC_SUCCESS);
451: };
452: const auto try_find_open_chunk = [&](bool serialize = false) {
453: PetscFunctionBegin;
454: for (auto &chunk : chunks_) {
455: PetscCall(chunk.claim(stream, req_size, success, serialize));
456: if (*success) {
457: *ptr = mem_ + chunk.start();
458: break;
459: }
460: }
461: PetscFunctionReturn(PETSC_SUCCESS);
462: };
463: const auto try_steal_other_stream_chunk = [&]() {
464: PetscFunctionBegin;
465: PetscCall(try_find_open_chunk(true));
466: PetscFunctionReturn(PETSC_SUCCESS);
467: };
469: // search previously distributed chunks, but only claim one if it is on the same stream
470: // as us
471: PetscCall(try_find_open_chunk());
473: // if we are here we couldn't reuse one of our own chunks so check first if the pool
474: // has room for a new one
475: if (!*success) PetscCall(try_create_chunk());
477: // try pruning dead chunks off the back, note we do this regardless of whether we are
478: // successful
479: while (chunks_.back().can_claim(stream, 0, false)) {
480: PetscCallCXX(chunks_.pop_back());
481: if (chunks_.empty()) {
482: // if chunks are empty it implies we have managed to claim (and subsequently destroy)
483: // our own chunk twice! something has gone wrong
484: PetscAssert(!*success, PETSC_COMM_SELF, PETSC_ERR_PLIB, "Successfully claimed a chunk (of size %zu, from block of size %zu) but have now managed to claim it for a second time (and destroyed it)!", req_size, size());
485: break;
486: }
487: }
489: // if previously unsuccessful see if enough space has opened up due to pruning. note that
490: // if the chunk list was emptied from the pruning this call must succeed in allocating a
491: // chunk, otherwise something is wrong
492: if (!*success) PetscCall(try_create_chunk());
494: // last resort, iterate over all chunks and see if we can steal one by waiting on the
495: // current owner to finish using it
496: if (!*success) PetscCall(try_steal_other_stream_chunk());
497: }
498: PetscFunctionReturn(PETSC_SUCCESS);
499: }
501: /*
502: MemoryBlock::try_deallocate_chunk - try to restore a chunk to this MemoryBlock
504: Input Parameters:
505: + ptr - ptr to restore
506: - stream - stream to restore the pointer on
508: Output Parameter:
509: . success - true if chunk was restored, false otherwise
511: Notes:
512: ptr is set to nullptr on successful restore, and is unchanged otherwise. If the ptr is owned
513: by this MemoryBlock then it is restored on stream. The same stream may receive ptr again
514: without synchronization, but other streams may not do so until either serializing or the
515: stream is idle again.
516: */
517: template <typename T, typename A, typename S>
518: inline PetscErrorCode MemoryBlock<T, A, S>::try_deallocate_chunk(T **ptr, const stream_type *stream, bool *success) noexcept
519: {
520: chunk_type *chunk = nullptr;
522: PetscFunctionBegin;
523: PetscCall(try_find_chunk(*ptr, &chunk));
524: if (chunk) {
525: PetscCall(chunk->release(stream));
526: *ptr = nullptr;
527: *success = true;
528: } else {
529: *success = false;
530: }
531: PetscFunctionReturn(PETSC_SUCCESS);
532: }
534: /*
535: MemoryBlock::try_find_chunk - try to find the chunk which owns ptr
537: Input Parameter:
538: . ptr - the pointer to look for
540: Output Parameter:
541: . ret_chunk - pointer to the owning chunk or nullptr if not found
542: */
543: template <typename T, typename A, typename S>
544: inline PetscErrorCode MemoryBlock<T, A, S>::try_find_chunk(const T *ptr, chunk_type **ret_chunk) noexcept
545: {
546: PetscFunctionBegin;
547: *ret_chunk = nullptr;
548: if (owns_pointer(ptr)) {
549: const auto offset = static_cast<size_type>(ptr - mem_);
551: for (auto &chunk : chunks_) {
552: if (chunk.contains(offset)) {
553: *ret_chunk = &chunk;
554: break;
555: }
556: }
558: PetscAssert(*ret_chunk, PETSC_COMM_SELF, PETSC_ERR_PLIB, "Failed to find %zu in block, even though it is within block range [%zu, %zu)", reinterpret_cast<uintptr_t>(ptr), reinterpret_cast<uintptr_t>(mem_), reinterpret_cast<uintptr_t>(std::next(mem_, size())));
559: }
560: PetscFunctionReturn(PETSC_SUCCESS);
561: }
563: namespace detail
564: {
566: template <typename T>
567: struct real_type {
568: using type = T;
569: };
571: template <>
572: struct real_type<PetscScalar> {
573: using type = PetscReal;
574: };
576: } // namespace detail
578: template <typename T>
579: struct SegmentedMemoryPoolAllocatorBase {
580: using value_type = T;
581: using size_type = std::size_t;
582: using real_value_type = typename detail::real_type<T>::type;
584: template <typename U>
585: static PetscErrorCode allocate(value_type **, size_type, const device::StreamBase<U> *) noexcept;
586: template <typename U>
587: static PetscErrorCode deallocate(value_type *, const device::StreamBase<U> *) noexcept;
588: template <typename U>
589: static PetscErrorCode zero(value_type *, size_type, const device::StreamBase<U> *) noexcept;
590: template <typename U>
591: static PetscErrorCode uninitialized_copy(value_type *, const value_type *, size_type, const device::StreamBase<U> *) noexcept;
592: template <typename U>
593: static PetscErrorCode set_canary(value_type *, size_type, const device::StreamBase<U> *) noexcept;
594: };
596: template <typename T>
597: template <typename U>
598: inline PetscErrorCode SegmentedMemoryPoolAllocatorBase<T>::allocate(value_type **ptr, size_type n, const device::StreamBase<U> *) noexcept
599: {
600: PetscFunctionBegin;
601: PetscCall(PetscMalloc1(n, ptr));
602: PetscFunctionReturn(PETSC_SUCCESS);
603: }
605: template <typename T>
606: template <typename U>
607: inline PetscErrorCode SegmentedMemoryPoolAllocatorBase<T>::deallocate(value_type *ptr, const device::StreamBase<U> *) noexcept
608: {
609: PetscFunctionBegin;
610: PetscCall(PetscFree(ptr));
611: PetscFunctionReturn(PETSC_SUCCESS);
612: }
614: template <typename T>
615: template <typename U>
616: inline PetscErrorCode SegmentedMemoryPoolAllocatorBase<T>::zero(value_type *ptr, size_type n, const device::StreamBase<U> *) noexcept
617: {
618: PetscFunctionBegin;
619: PetscCall(PetscArrayzero(ptr, n));
620: PetscFunctionReturn(PETSC_SUCCESS);
621: }
623: template <typename T>
624: template <typename U>
625: inline PetscErrorCode SegmentedMemoryPoolAllocatorBase<T>::uninitialized_copy(value_type *dest, const value_type *src, size_type n, const device::StreamBase<U> *) noexcept
626: {
627: PetscFunctionBegin;
628: PetscCall(PetscArraycpy(dest, src, n));
629: PetscFunctionReturn(PETSC_SUCCESS);
630: }
632: template <typename T>
633: template <typename U>
634: inline PetscErrorCode SegmentedMemoryPoolAllocatorBase<T>::set_canary(value_type *ptr, size_type n, const device::StreamBase<U> *) noexcept
635: {
636: using limit_type = std::numeric_limits<real_value_type>;
637: constexpr value_type canary = limit_type::has_signaling_NaN ? limit_type::signaling_NaN() : limit_type::max();
639: PetscFunctionBegin;
640: for (size_type i = 0; i < n; ++i) ptr[i] = canary;
641: PetscFunctionReturn(PETSC_SUCCESS);
642: }
644: } // namespace impl
646: // ==========================================================================================
647: // SegmentedMemoryPool
648: //
649: // Stream-aware async memory allocator. Holds a list of memory "blocks" which each control an
650: // allocated buffer. This buffer is further split into memory "chunks" which control
651: // consecutive, non-overlapping regions of the block. Chunks may be in 1 of 2 states:
652: //
653: // 1. Open:
654: // The chunk is free to be claimed by the next suitable allocation request. If the
655: // allocation request is made on the same stream as the chunk was deallocated on, no
656: // serialization needs to occur. If not, the allocating stream must wait for the
657: // event. Claiming the chunk "closes" the chunk.
658: //
659: // 2. Closed:
660: // The chunk has been claimed by an allocation request. It cannot be opened again until it
661: // is deallocated; doing so "opens" the chunk.
662: //
663: // Note that there does not need to be a chunk for every region, chunks are created to satisfy
664: // an allocation request.
665: //
666: // Thus there is usually a region of "unallocated" memory at the end of the buffer, which may
667: // be claimed by a newly created chunk if existing chunks cannot satisfy the allocation
668: // request. This region exists _only_ at the end, as there are no gaps between chunks.
669: //
670: //
671: // |-----------------------------------------------------------------------------------------
672: // | SegmentedMemoryPool
673: // |
674: // | ||-------------||
675: // | || || -------------------------------------------------------------------
676: // | || || | AAAAAAAAAAAAAABBBBBBBCCCCCCCCCCCCCCCCCCCCDDDDDDDDDDDDDXXXXXXXX...
677: // | || || | | | | | |
678: // | || || | x-----x-------x-----xx---------x---------x------x-----x
679: // | || MemoryBlock || -> | ------|-------------|----------|----------------|--------
680: // | || || | | MemoryChunk | MemoryChunk | MemoryChunk | MemoryChunk |
681: // | || || | ---------------------------------------------------------
682: // | || || -------------------------------------------------------------------
683: // | ||-------------||
684: // | || ||
685: // | || ... ||
686: // | || ||
687: // ==========================================================================================
689: template <typename MemType, typename StreamType = device::DefaultStream, typename AllocType = impl::SegmentedMemoryPoolAllocatorBase<MemType>, std::size_t DefaultChunkSize = 256>
690: class SegmentedMemoryPool;
692: // The actual memory pool class. It is in essence just a wrapper for a list of MemoryBlocks.
693: template <typename MemType, typename StreamType, typename AllocType, std::size_t DefaultChunkSize>
694: class SegmentedMemoryPool : public RegisterFinalizeable<SegmentedMemoryPool<MemType, StreamType, AllocType, DefaultChunkSize>> {
695: public:
696: using value_type = MemType;
697: using stream_type = StreamType;
698: using allocator_type = AllocType;
699: using block_type = impl::MemoryBlock<value_type, allocator_type, stream_type>;
700: using pool_type = std::deque<block_type>;
701: using size_type = typename block_type::size_type;
703: explicit SegmentedMemoryPool(AllocType = AllocType{}, std::size_t = DefaultChunkSize) noexcept(std::is_nothrow_default_constructible<pool_type>::value);
705: PetscErrorCode allocate(PetscInt, value_type **, const stream_type *, size_type = std::alignment_of<MemType>::value) noexcept;
706: PetscErrorCode deallocate(value_type **, const stream_type *) noexcept;
707: PetscErrorCode reallocate(PetscInt, value_type **, const stream_type *) noexcept;
709: private:
710: pool_type pool_;
711: allocator_type allocator_;
712: size_type chunk_size_;
714: PetscErrorCode make_block_(size_type, const stream_type *) noexcept;
716: friend class RegisterFinalizeable<SegmentedMemoryPool<MemType, StreamType, AllocType, DefaultChunkSize>>;
717: PetscErrorCode register_finalize_(const stream_type *) noexcept;
718: PetscErrorCode finalize_() noexcept;
720: PetscErrorCode allocate_(size_type, value_type **, const stream_type *) noexcept;
721: };
723: // ==========================================================================================
724: // SegmentedMemoryPool - Private API
725: // ==========================================================================================
727: template <typename MemType, typename StreamType, typename AllocType, std::size_t DefaultChunkSize>
728: inline PetscErrorCode SegmentedMemoryPool<MemType, StreamType, AllocType, DefaultChunkSize>::make_block_(size_type size, const stream_type *stream) noexcept
729: {
730: const auto block_size = std::max(size, chunk_size_);
732: PetscFunctionBegin;
733: PetscCallCXX(pool_.emplace_back(&allocator_, block_size, stream));
734: PetscCall(PetscInfo(nullptr, "Allocated new block of size %zu, total %zu blocks\n", block_size, pool_.size()));
735: PetscFunctionReturn(PETSC_SUCCESS);
736: }
738: template <typename MemType, typename StreamType, typename AllocType, std::size_t DefaultChunkSize>
739: inline PetscErrorCode SegmentedMemoryPool<MemType, StreamType, AllocType, DefaultChunkSize>::register_finalize_(const stream_type *stream) noexcept
740: {
741: PetscFunctionBegin;
742: PetscCall(make_block_(chunk_size_, stream));
743: PetscFunctionReturn(PETSC_SUCCESS);
744: }
746: template <typename MemType, typename StreamType, typename AllocType, std::size_t DefaultChunkSize>
747: inline PetscErrorCode SegmentedMemoryPool<MemType, StreamType, AllocType, DefaultChunkSize>::finalize_() noexcept
748: {
749: PetscFunctionBegin;
750: PetscCallCXX(pool_.clear());
751: chunk_size_ = DefaultChunkSize;
752: PetscFunctionReturn(PETSC_SUCCESS);
753: }
755: template <typename MemType, typename StreamType, typename AllocType, std::size_t DefaultChunkSize>
756: inline PetscErrorCode SegmentedMemoryPool<MemType, StreamType, AllocType, DefaultChunkSize>::allocate_(size_type size, value_type **ptr, const stream_type *stream) noexcept
757: {
758: auto found = false;
760: PetscFunctionBegin;
761: PetscCall(this->register_finalize(stream));
762: for (auto &block : pool_) {
763: PetscCall(block.try_allocate_chunk(size, ptr, stream, &found));
764: if (PetscLikely(found)) PetscFunctionReturn(PETSC_SUCCESS);
765: }
767: PetscCall(PetscInfo(nullptr, "Could not find an open block in the pool (%zu blocks) (requested size %zu), allocating new block\n", pool_.size(), size));
768: // if we are here we couldn't find an open block in the pool, so make a new block
769: PetscCall(make_block_(size, stream));
770: // and assign it
771: PetscCall(pool_.back().try_allocate_chunk(size, ptr, stream, &found));
772: PetscAssert(found, PETSC_COMM_SELF, PETSC_ERR_MEM, "Failed to get a suitable memory chunk (of size %zu) from newly allocated memory block (size %zu)", size, pool_.back().size());
773: PetscFunctionReturn(PETSC_SUCCESS);
774: }
776: // ==========================================================================================
777: // SegmentedMemoryPool - Public API
778: // ==========================================================================================
780: template <typename MemType, typename StreamType, typename AllocType, std::size_t DefaultChunkSize>
781: inline SegmentedMemoryPool<MemType, StreamType, AllocType, DefaultChunkSize>::SegmentedMemoryPool(AllocType alloc, std::size_t size) noexcept(std::is_nothrow_default_constructible<pool_type>::value) : allocator_(std::move(alloc)), chunk_size_(size)
782: {
783: }
785: /*
786: SegmentedMemoryPool::allocate - get an allocation from the memory pool
788: Input Parameters:
789: + req_size - size (in elements) to get
790: . ptr - the pointer to hold the allocation
791: - stream - the stream on which to get the allocation
793: Output Parameter:
794: . ptr - the pointer holding the allocation
796: Notes:
797: req_size cannot be negative. If req_size if zero, ptr is set to nullptr
798: */
799: template <typename MemType, typename StreamType, typename AllocType, std::size_t DefaultChunkSize>
800: inline PetscErrorCode SegmentedMemoryPool<MemType, StreamType, AllocType, DefaultChunkSize>::allocate(PetscInt req_size, value_type **ptr, const stream_type *stream, size_type alignment) noexcept
801: {
802: value_type *ret_ptr = nullptr;
804: PetscFunctionBegin;
805: PetscAssert(req_size >= 0, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "Requested memory amount (%" PetscInt_FMT ") must be >= 0", req_size);
808: if (req_size) {
809: const auto size = static_cast<size_type>(req_size);
810: auto aligned_size = alignment == alignof(char) ? size : size + alignment;
811: void *vptr = nullptr;
813: PetscCall(allocate_(aligned_size, &ret_ptr, stream));
814: vptr = ret_ptr;
815: std::align(alignment, size, vptr, aligned_size);
816: ret_ptr = reinterpret_cast<value_type *>(vptr);
817: // sets memory to NaN or infinity depending on the type to catch out uninitialized memory
818: // accesses.
819: if (PetscDefined(USE_DEBUG)) PetscCall(allocator_.set_canary(ret_ptr, size, stream));
820: }
821: *ptr = ret_ptr;
822: PetscFunctionReturn(PETSC_SUCCESS);
823: }
825: /*
826: SegmentedMemoryPool::deallocate - release a pointer back to the memory pool
828: Input Parameters:
829: + ptr - the pointer to release
830: - stream - the stream to release it on
832: Notes:
833: If ptr is not owned by the pool it is unchanged.
834: */
835: template <typename MemType, typename StreamType, typename AllocType, std::size_t DefaultChunkSize>
836: inline PetscErrorCode SegmentedMemoryPool<MemType, StreamType, AllocType, DefaultChunkSize>::deallocate(value_type **ptr, const stream_type *stream) noexcept
837: {
838: PetscFunctionBegin;
841: // nobody owns a nullptr, and if they do then they have bigger problems
842: if (!*ptr) PetscFunctionReturn(PETSC_SUCCESS);
843: for (auto &block : pool_) {
844: auto found = false;
846: PetscCall(block.try_deallocate_chunk(ptr, stream, &found));
847: if (PetscLikely(found)) break;
848: }
849: PetscFunctionReturn(PETSC_SUCCESS);
850: }
852: /*
853: SegmentedMemoryPool::reallocate - Resize an allocated buffer
855: Input Parameters:
856: + new_req_size - the new buffer size
857: . ptr - pointer to the buffer
858: - stream - stream to resize with
860: Output Parameter:
861: . ptr - pointer to the new region
863: Notes:
864: ptr must have been allocated by the pool.
866: It's OK to shrink the buffer, even down to 0 (in which case it is just deallocated).
867: */
868: template <typename MemType, typename StreamType, typename AllocType, std::size_t DefaultChunkSize>
869: inline PetscErrorCode SegmentedMemoryPool<MemType, StreamType, AllocType, DefaultChunkSize>::reallocate(PetscInt new_req_size, value_type **ptr, const stream_type *stream) noexcept
870: {
871: using chunk_type = typename block_type::chunk_type;
873: const auto new_size = static_cast<size_type>(new_req_size);
874: const auto old_ptr = *ptr;
875: chunk_type *chunk = nullptr;
877: PetscFunctionBegin;
878: PetscAssert(new_req_size >= 0, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "Requested memory amount (%" PetscInt_FMT ") must be >= 0", new_req_size);
882: // if reallocating to zero, just free
883: if (PetscUnlikely(new_size == 0)) {
884: PetscCall(deallocate(ptr, stream));
885: PetscFunctionReturn(PETSC_SUCCESS);
886: }
888: // search the blocks for the owning chunk
889: for (auto &block : pool_) {
890: PetscCall(block.try_find_chunk(old_ptr, &chunk));
891: if (chunk) break; // found
892: }
893: PetscAssert(chunk, PETSC_COMM_SELF, PETSC_ERR_ARG_WRONG, "Memory pool does not own %p, so cannot reallocate it", *ptr);
895: if (chunk->capacity() < new_size) {
896: // chunk does not have enough room, need to grab a fresh chunk and copy to it
897: *ptr = nullptr;
898: PetscCall(chunk->release(stream));
899: PetscCall(allocate(new_size, ptr, stream));
900: PetscCall(allocator_.uninitialized_copy(*ptr, old_ptr, new_size, stream));
901: } else {
902: // chunk had enough room we can simply grow (or shrink) to fit the new size
903: PetscCall(chunk->resize(new_size));
904: }
905: PetscFunctionReturn(PETSC_SUCCESS);
906: }
908: } // namespace memory
910: } // namespace Petsc
912: #endif // PETSC_SEGMENTEDMEMPOOL_HPP