| /*---------------------------------------------------------------------------- |
| Copyright (c) 2018-2020, Microsoft Research, Daan Leijen |
| This is free software; you can redistribute it and/or modify it under the |
| terms of the MIT license. A copy of the license can be found in the file |
| "LICENSE" at the root of this distribution. |
| -----------------------------------------------------------------------------*/ |
| |
| /* ----------------------------------------------------------- |
| The core of the allocator. Every segment contains |
| pages of a certain block size. The main function |
| exported is `mi_malloc_generic`. |
| ----------------------------------------------------------- */ |
| |
| #include "mimalloc.h" |
| #include "mimalloc/internal.h" |
| #include "mimalloc/atomic.h" |
| |
| /* ----------------------------------------------------------- |
| Definition of page queues for each block size |
| ----------------------------------------------------------- */ |
| |
| #define MI_IN_PAGE_C |
| #include "page-queue.c" |
| #undef MI_IN_PAGE_C |
| |
| |
| /* ----------------------------------------------------------- |
| Page helpers |
| ----------------------------------------------------------- */ |
| |
| // Index a block in a page |
| static inline mi_block_t* mi_page_block_at(const mi_page_t* page, void* page_start, size_t block_size, size_t i) { |
| MI_UNUSED(page); |
| mi_assert_internal(page != NULL); |
| mi_assert_internal(i <= page->reserved); |
| return (mi_block_t*)((uint8_t*)page_start + (i * block_size)); |
| } |
| |
| static void mi_page_init(mi_heap_t* heap, mi_page_t* page, size_t size, mi_tld_t* tld); |
| static void mi_page_extend_free(mi_heap_t* heap, mi_page_t* page, mi_tld_t* tld); |
| |
| #if (MI_DEBUG>=3) |
| static size_t mi_page_list_count(mi_page_t* page, mi_block_t* head) { |
| size_t count = 0; |
| while (head != NULL) { |
| mi_assert_internal(page == _mi_ptr_page(head)); |
| count++; |
| head = mi_block_next(page, head); |
| } |
| return count; |
| } |
| |
| /* |
| // Start of the page available memory |
| static inline uint8_t* mi_page_area(const mi_page_t* page) { |
| return _mi_page_start(_mi_page_segment(page), page, NULL); |
| } |
| */ |
| |
| static bool mi_page_list_is_valid(mi_page_t* page, mi_block_t* p) { |
| size_t psize; |
| uint8_t* page_area = _mi_page_start(_mi_page_segment(page), page, &psize); |
| mi_block_t* start = (mi_block_t*)page_area; |
| mi_block_t* end = (mi_block_t*)(page_area + psize); |
| while(p != NULL) { |
| if (p < start || p >= end) return false; |
| p = mi_block_next(page, p); |
| } |
| #if MI_DEBUG>3 // generally too expensive to check this |
| if (page->free_is_zero) { |
| const size_t ubsize = mi_page_usable_block_size(page); |
| for (mi_block_t* block = page->free; block != NULL; block = mi_block_next(page, block)) { |
| mi_assert_expensive(mi_mem_is_zero(block + 1, ubsize - sizeof(mi_block_t))); |
| } |
| } |
| #endif |
| return true; |
| } |
| |
| static bool mi_page_is_valid_init(mi_page_t* page) { |
| mi_assert_internal(page->xblock_size > 0); |
| mi_assert_internal(page->used <= page->capacity); |
| mi_assert_internal(page->capacity <= page->reserved); |
| |
| mi_segment_t* segment = _mi_page_segment(page); |
| uint8_t* start = _mi_page_start(segment,page,NULL); |
| mi_assert_internal(start == _mi_segment_page_start(segment,page,NULL)); |
| //const size_t bsize = mi_page_block_size(page); |
| //mi_assert_internal(start + page->capacity*page->block_size == page->top); |
| |
| mi_assert_internal(mi_page_list_is_valid(page,page->free)); |
| mi_assert_internal(mi_page_list_is_valid(page,page->local_free)); |
| |
| #if MI_DEBUG>3 // generally too expensive to check this |
| if (page->free_is_zero) { |
| const size_t ubsize = mi_page_usable_block_size(page); |
| for(mi_block_t* block = page->free; block != NULL; block = mi_block_next(page,block)) { |
| mi_assert_expensive(mi_mem_is_zero(block + 1, ubsize - sizeof(mi_block_t))); |
| } |
| } |
| #endif |
| |
| #if !MI_TRACK_ENABLED && !MI_TSAN |
| mi_block_t* tfree = mi_page_thread_free(page); |
| mi_assert_internal(mi_page_list_is_valid(page, tfree)); |
| //size_t tfree_count = mi_page_list_count(page, tfree); |
| //mi_assert_internal(tfree_count <= page->thread_freed + 1); |
| #endif |
| |
| size_t free_count = mi_page_list_count(page, page->free) + mi_page_list_count(page, page->local_free); |
| mi_assert_internal(page->used + free_count == page->capacity); |
| |
| return true; |
| } |
| |
| extern bool _mi_process_is_initialized; // has mi_process_init been called? |
| |
| bool _mi_page_is_valid(mi_page_t* page) { |
| mi_assert_internal(mi_page_is_valid_init(page)); |
| #if MI_SECURE |
| mi_assert_internal(page->keys[0] != 0); |
| #endif |
| if (mi_page_heap(page)!=NULL) { |
| mi_segment_t* segment = _mi_page_segment(page); |
| |
| mi_assert_internal(!_mi_process_is_initialized || segment->thread_id==0 || segment->thread_id == mi_page_heap(page)->thread_id); |
| #if MI_HUGE_PAGE_ABANDON |
| if (segment->kind != MI_SEGMENT_HUGE) |
| #endif |
| { |
| mi_page_queue_t* pq = mi_page_queue_of(page); |
| mi_assert_internal(mi_page_queue_contains(pq, page)); |
| mi_assert_internal(pq->block_size==mi_page_block_size(page) || mi_page_block_size(page) > MI_MEDIUM_OBJ_SIZE_MAX || mi_page_is_in_full(page)); |
| mi_assert_internal(mi_heap_contains_queue(mi_page_heap(page),pq)); |
| } |
| } |
| return true; |
| } |
| #endif |
| |
| void _mi_page_use_delayed_free(mi_page_t* page, mi_delayed_t delay, bool override_never) { |
| while (!_mi_page_try_use_delayed_free(page, delay, override_never)) { |
| mi_atomic_yield(); |
| } |
| } |
| |
| bool _mi_page_try_use_delayed_free(mi_page_t* page, mi_delayed_t delay, bool override_never) { |
| mi_thread_free_t tfreex; |
| mi_delayed_t old_delay; |
| mi_thread_free_t tfree; |
| size_t yield_count = 0; |
| do { |
| tfree = mi_atomic_load_acquire(&page->xthread_free); // note: must acquire as we can break/repeat this loop and not do a CAS; |
| tfreex = mi_tf_set_delayed(tfree, delay); |
| old_delay = mi_tf_delayed(tfree); |
| if mi_unlikely(old_delay == MI_DELAYED_FREEING) { |
| if (yield_count >= 4) return false; // give up after 4 tries |
| yield_count++; |
| mi_atomic_yield(); // delay until outstanding MI_DELAYED_FREEING are done. |
| // tfree = mi_tf_set_delayed(tfree, MI_NO_DELAYED_FREE); // will cause CAS to busy fail |
| } |
| else if (delay == old_delay) { |
| break; // avoid atomic operation if already equal |
| } |
| else if (!override_never && old_delay == MI_NEVER_DELAYED_FREE) { |
| break; // leave never-delayed flag set |
| } |
| } while ((old_delay == MI_DELAYED_FREEING) || |
| !mi_atomic_cas_weak_release(&page->xthread_free, &tfree, tfreex)); |
| |
| return true; // success |
| } |
| |
| /* ----------------------------------------------------------- |
| Page collect the `local_free` and `thread_free` lists |
| ----------------------------------------------------------- */ |
| |
| // Collect the local `thread_free` list using an atomic exchange. |
| // Note: The exchange must be done atomically as this is used right after |
| // moving to the full list in `mi_page_collect_ex` and we need to |
| // ensure that there was no race where the page became unfull just before the move. |
| static void _mi_page_thread_free_collect(mi_page_t* page) |
| { |
| mi_block_t* head; |
| mi_thread_free_t tfreex; |
| mi_thread_free_t tfree = mi_atomic_load_relaxed(&page->xthread_free); |
| do { |
| head = mi_tf_block(tfree); |
| tfreex = mi_tf_set_block(tfree,NULL); |
| } while (!mi_atomic_cas_weak_acq_rel(&page->xthread_free, &tfree, tfreex)); |
| |
| // return if the list is empty |
| if (head == NULL) return; |
| |
| // find the tail -- also to get a proper count (without data races) |
| uint32_t max_count = page->capacity; // cannot collect more than capacity |
| uint32_t count = 1; |
| mi_block_t* tail = head; |
| mi_block_t* next; |
| while ((next = mi_block_next(page,tail)) != NULL && count <= max_count) { |
| count++; |
| tail = next; |
| } |
| // if `count > max_count` there was a memory corruption (possibly infinite list due to double multi-threaded free) |
| if (count > max_count) { |
| _mi_error_message(EFAULT, "corrupted thread-free list\n"); |
| return; // the thread-free items cannot be freed |
| } |
| |
| // and append the current local free list |
| mi_block_set_next(page,tail, page->local_free); |
| page->local_free = head; |
| |
| // update counts now |
| page->used -= count; |
| } |
| |
| void _mi_page_free_collect(mi_page_t* page, bool force) { |
| mi_assert_internal(page!=NULL); |
| |
| // collect the thread free list |
| if (force || mi_page_thread_free(page) != NULL) { // quick test to avoid an atomic operation |
| _mi_page_thread_free_collect(page); |
| } |
| |
| // and the local free list |
| if (page->local_free != NULL) { |
| if mi_likely(page->free == NULL) { |
| // usual case |
| page->free = page->local_free; |
| page->local_free = NULL; |
| page->free_is_zero = false; |
| } |
| else if (force) { |
| // append -- only on shutdown (force) as this is a linear operation |
| mi_block_t* tail = page->local_free; |
| mi_block_t* next; |
| while ((next = mi_block_next(page, tail)) != NULL) { |
| tail = next; |
| } |
| mi_block_set_next(page, tail, page->free); |
| page->free = page->local_free; |
| page->local_free = NULL; |
| page->free_is_zero = false; |
| } |
| } |
| |
| mi_assert_internal(!force || page->local_free == NULL); |
| } |
| |
| |
| |
| /* ----------------------------------------------------------- |
| Page fresh and retire |
| ----------------------------------------------------------- */ |
| |
| // called from segments when reclaiming abandoned pages |
| void _mi_page_reclaim(mi_heap_t* heap, mi_page_t* page) { |
| mi_assert_expensive(mi_page_is_valid_init(page)); |
| |
| mi_assert_internal(mi_page_heap(page) == heap); |
| mi_assert_internal(mi_page_thread_free_flag(page) != MI_NEVER_DELAYED_FREE); |
| #if MI_HUGE_PAGE_ABANDON |
| mi_assert_internal(_mi_page_segment(page)->kind != MI_SEGMENT_HUGE); |
| #endif |
| |
| // TODO: push on full queue immediately if it is full? |
| mi_page_queue_t* pq = mi_page_queue(heap, mi_page_block_size(page)); |
| mi_page_queue_push(heap, pq, page); |
| mi_assert_expensive(_mi_page_is_valid(page)); |
| } |
| |
| // allocate a fresh page from a segment |
| static mi_page_t* mi_page_fresh_alloc(mi_heap_t* heap, mi_page_queue_t* pq, size_t block_size, size_t page_alignment) { |
| #if !MI_HUGE_PAGE_ABANDON |
| mi_assert_internal(pq != NULL); |
| mi_assert_internal(mi_heap_contains_queue(heap, pq)); |
| mi_assert_internal(page_alignment > 0 || block_size > MI_MEDIUM_OBJ_SIZE_MAX || block_size == pq->block_size); |
| #endif |
| mi_page_t* page = _mi_segment_page_alloc(heap, block_size, page_alignment, &heap->tld->segments, &heap->tld->os); |
| if (page == NULL) { |
| // this may be out-of-memory, or an abandoned page was reclaimed (and in our queue) |
| return NULL; |
| } |
| mi_assert_internal(page_alignment >0 || block_size > MI_MEDIUM_OBJ_SIZE_MAX || _mi_page_segment(page)->kind != MI_SEGMENT_HUGE); |
| mi_assert_internal(pq!=NULL || page->xblock_size != 0); |
| mi_assert_internal(pq!=NULL || mi_page_block_size(page) >= block_size); |
| // a fresh page was found, initialize it |
| const size_t full_block_size = ((pq == NULL || mi_page_queue_is_huge(pq)) ? mi_page_block_size(page) : block_size); // see also: mi_segment_huge_page_alloc |
| mi_assert_internal(full_block_size >= block_size); |
| mi_page_init(heap, page, full_block_size, heap->tld); |
| mi_heap_stat_increase(heap, pages, 1); |
| if (pq != NULL) { mi_page_queue_push(heap, pq, page); } |
| mi_assert_expensive(_mi_page_is_valid(page)); |
| return page; |
| } |
| |
| // Get a fresh page to use |
| static mi_page_t* mi_page_fresh(mi_heap_t* heap, mi_page_queue_t* pq) { |
| mi_assert_internal(mi_heap_contains_queue(heap, pq)); |
| mi_page_t* page = mi_page_fresh_alloc(heap, pq, pq->block_size, 0); |
| if (page==NULL) return NULL; |
| mi_assert_internal(pq->block_size==mi_page_block_size(page)); |
| mi_assert_internal(pq==mi_page_queue(heap, mi_page_block_size(page))); |
| return page; |
| } |
| |
| /* ----------------------------------------------------------- |
| Do any delayed frees |
| (put there by other threads if they deallocated in a full page) |
| ----------------------------------------------------------- */ |
| void _mi_heap_delayed_free_all(mi_heap_t* heap) { |
| while (!_mi_heap_delayed_free_partial(heap)) { |
| mi_atomic_yield(); |
| } |
| } |
| |
| // returns true if all delayed frees were processed |
| bool _mi_heap_delayed_free_partial(mi_heap_t* heap) { |
| // take over the list (note: no atomic exchange since it is often NULL) |
| mi_block_t* block = mi_atomic_load_ptr_relaxed(mi_block_t, &heap->thread_delayed_free); |
| while (block != NULL && !mi_atomic_cas_ptr_weak_acq_rel(mi_block_t, &heap->thread_delayed_free, &block, NULL)) { /* nothing */ }; |
| bool all_freed = true; |
| |
| // and free them all |
| while(block != NULL) { |
| mi_block_t* next = mi_block_nextx(heap,block, heap->keys); |
| // use internal free instead of regular one to keep stats etc correct |
| if (!_mi_free_delayed_block(block)) { |
| // we might already start delayed freeing while another thread has not yet |
| // reset the delayed_freeing flag; in that case delay it further by reinserting the current block |
| // into the delayed free list |
| all_freed = false; |
| mi_block_t* dfree = mi_atomic_load_ptr_relaxed(mi_block_t, &heap->thread_delayed_free); |
| do { |
| mi_block_set_nextx(heap, block, dfree, heap->keys); |
| } while (!mi_atomic_cas_ptr_weak_release(mi_block_t,&heap->thread_delayed_free, &dfree, block)); |
| } |
| block = next; |
| } |
| return all_freed; |
| } |
| |
| /* ----------------------------------------------------------- |
| Unfull, abandon, free and retire |
| ----------------------------------------------------------- */ |
| |
| // Move a page from the full list back to a regular list |
| void _mi_page_unfull(mi_page_t* page) { |
| mi_assert_internal(page != NULL); |
| mi_assert_expensive(_mi_page_is_valid(page)); |
| mi_assert_internal(mi_page_is_in_full(page)); |
| if (!mi_page_is_in_full(page)) return; |
| |
| mi_heap_t* heap = mi_page_heap(page); |
| mi_page_queue_t* pqfull = &heap->pages[MI_BIN_FULL]; |
| mi_page_set_in_full(page, false); // to get the right queue |
| mi_page_queue_t* pq = mi_heap_page_queue_of(heap, page); |
| mi_page_set_in_full(page, true); |
| mi_page_queue_enqueue_from(pq, pqfull, page); |
| } |
| |
| static void mi_page_to_full(mi_page_t* page, mi_page_queue_t* pq) { |
| mi_assert_internal(pq == mi_page_queue_of(page)); |
| mi_assert_internal(!mi_page_immediate_available(page)); |
| mi_assert_internal(!mi_page_is_in_full(page)); |
| |
| if (mi_page_is_in_full(page)) return; |
| mi_page_queue_enqueue_from(&mi_page_heap(page)->pages[MI_BIN_FULL], pq, page); |
| _mi_page_free_collect(page,false); // try to collect right away in case another thread freed just before MI_USE_DELAYED_FREE was set |
| } |
| |
| |
| // Abandon a page with used blocks at the end of a thread. |
| // Note: only call if it is ensured that no references exist from |
| // the `page->heap->thread_delayed_free` into this page. |
| // Currently only called through `mi_heap_collect_ex` which ensures this. |
| void _mi_page_abandon(mi_page_t* page, mi_page_queue_t* pq) { |
| mi_assert_internal(page != NULL); |
| mi_assert_expensive(_mi_page_is_valid(page)); |
| mi_assert_internal(pq == mi_page_queue_of(page)); |
| mi_assert_internal(mi_page_heap(page) != NULL); |
| |
| mi_heap_t* pheap = mi_page_heap(page); |
| |
| // remove from our page list |
| mi_segments_tld_t* segments_tld = &pheap->tld->segments; |
| mi_page_queue_remove(pq, page); |
| |
| // page is no longer associated with our heap |
| mi_assert_internal(mi_page_thread_free_flag(page)==MI_NEVER_DELAYED_FREE); |
| mi_page_set_heap(page, NULL); |
| |
| #if (MI_DEBUG>1) && !MI_TRACK_ENABLED |
| // check there are no references left.. |
| for (mi_block_t* block = (mi_block_t*)pheap->thread_delayed_free; block != NULL; block = mi_block_nextx(pheap, block, pheap->keys)) { |
| mi_assert_internal(_mi_ptr_page(block) != page); |
| } |
| #endif |
| |
| // and abandon it |
| mi_assert_internal(mi_page_heap(page) == NULL); |
| _mi_segment_page_abandon(page,segments_tld); |
| } |
| |
| |
| // Free a page with no more free blocks |
| void _mi_page_free(mi_page_t* page, mi_page_queue_t* pq, bool force) { |
| mi_assert_internal(page != NULL); |
| mi_assert_expensive(_mi_page_is_valid(page)); |
| mi_assert_internal(pq == mi_page_queue_of(page)); |
| mi_assert_internal(mi_page_all_free(page)); |
| mi_assert_internal(mi_page_thread_free_flag(page)!=MI_DELAYED_FREEING); |
| |
| // no more aligned blocks in here |
| mi_page_set_has_aligned(page, false); |
| |
| mi_heap_t* heap = mi_page_heap(page); |
| |
| // remove from the page list |
| // (no need to do _mi_heap_delayed_free first as all blocks are already free) |
| mi_segments_tld_t* segments_tld = &heap->tld->segments; |
| mi_page_queue_remove(pq, page); |
| |
| // and free it |
| mi_page_set_heap(page,NULL); |
| _mi_segment_page_free(page, force, segments_tld); |
| } |
| |
| // Retire parameters |
| #define MI_MAX_RETIRE_SIZE (MI_MEDIUM_OBJ_SIZE_MAX) |
| #define MI_RETIRE_CYCLES (16) |
| |
| // Retire a page with no more used blocks |
| // Important to not retire too quickly though as new |
| // allocations might coming. |
| // Note: called from `mi_free` and benchmarks often |
| // trigger this due to freeing everything and then |
| // allocating again so careful when changing this. |
| void _mi_page_retire(mi_page_t* page) mi_attr_noexcept { |
| mi_assert_internal(page != NULL); |
| mi_assert_expensive(_mi_page_is_valid(page)); |
| mi_assert_internal(mi_page_all_free(page)); |
| |
| mi_page_set_has_aligned(page, false); |
| |
| // don't retire too often.. |
| // (or we end up retiring and re-allocating most of the time) |
| // NOTE: refine this more: we should not retire if this |
| // is the only page left with free blocks. It is not clear |
| // how to check this efficiently though... |
| // for now, we don't retire if it is the only page left of this size class. |
| mi_page_queue_t* pq = mi_page_queue_of(page); |
| if mi_likely(page->xblock_size <= MI_MAX_RETIRE_SIZE && !mi_page_queue_is_special(pq)) { // not too large && not full or huge queue? |
| if (pq->last==page && pq->first==page) { // the only page in the queue? |
| mi_stat_counter_increase(_mi_stats_main.page_no_retire,1); |
| page->retire_expire = 1 + (page->xblock_size <= MI_SMALL_OBJ_SIZE_MAX ? MI_RETIRE_CYCLES : MI_RETIRE_CYCLES/4); |
| mi_heap_t* heap = mi_page_heap(page); |
| mi_assert_internal(pq >= heap->pages); |
| const size_t index = pq - heap->pages; |
| mi_assert_internal(index < MI_BIN_FULL && index < MI_BIN_HUGE); |
| if (index < heap->page_retired_min) heap->page_retired_min = index; |
| if (index > heap->page_retired_max) heap->page_retired_max = index; |
| mi_assert_internal(mi_page_all_free(page)); |
| return; // dont't free after all |
| } |
| } |
| _mi_page_free(page, pq, false); |
| } |
| |
| // free retired pages: we don't need to look at the entire queues |
| // since we only retire pages that are at the head position in a queue. |
| void _mi_heap_collect_retired(mi_heap_t* heap, bool force) { |
| size_t min = MI_BIN_FULL; |
| size_t max = 0; |
| for(size_t bin = heap->page_retired_min; bin <= heap->page_retired_max; bin++) { |
| mi_page_queue_t* pq = &heap->pages[bin]; |
| mi_page_t* page = pq->first; |
| if (page != NULL && page->retire_expire != 0) { |
| if (mi_page_all_free(page)) { |
| page->retire_expire--; |
| if (force || page->retire_expire == 0) { |
| _mi_page_free(pq->first, pq, force); |
| } |
| else { |
| // keep retired, update min/max |
| if (bin < min) min = bin; |
| if (bin > max) max = bin; |
| } |
| } |
| else { |
| page->retire_expire = 0; |
| } |
| } |
| } |
| heap->page_retired_min = min; |
| heap->page_retired_max = max; |
| } |
| |
| |
| /* ----------------------------------------------------------- |
| Initialize the initial free list in a page. |
| In secure mode we initialize a randomized list by |
| alternating between slices. |
| ----------------------------------------------------------- */ |
| |
| #define MI_MAX_SLICE_SHIFT (6) // at most 64 slices |
| #define MI_MAX_SLICES (1UL << MI_MAX_SLICE_SHIFT) |
| #define MI_MIN_SLICES (2) |
| |
| static void mi_page_free_list_extend_secure(mi_heap_t* const heap, mi_page_t* const page, const size_t bsize, const size_t extend, mi_stats_t* const stats) { |
| MI_UNUSED(stats); |
| #if (MI_SECURE<=2) |
| mi_assert_internal(page->free == NULL); |
| mi_assert_internal(page->local_free == NULL); |
| #endif |
| mi_assert_internal(page->capacity + extend <= page->reserved); |
| mi_assert_internal(bsize == mi_page_block_size(page)); |
| void* const page_area = _mi_page_start(_mi_page_segment(page), page, NULL); |
| |
| // initialize a randomized free list |
| // set up `slice_count` slices to alternate between |
| size_t shift = MI_MAX_SLICE_SHIFT; |
| while ((extend >> shift) == 0) { |
| shift--; |
| } |
| const size_t slice_count = (size_t)1U << shift; |
| const size_t slice_extend = extend / slice_count; |
| mi_assert_internal(slice_extend >= 1); |
| mi_block_t* blocks[MI_MAX_SLICES]; // current start of the slice |
| size_t counts[MI_MAX_SLICES]; // available objects in the slice |
| for (size_t i = 0; i < slice_count; i++) { |
| blocks[i] = mi_page_block_at(page, page_area, bsize, page->capacity + i*slice_extend); |
| counts[i] = slice_extend; |
| } |
| counts[slice_count-1] += (extend % slice_count); // final slice holds the modulus too (todo: distribute evenly?) |
| |
| // and initialize the free list by randomly threading through them |
| // set up first element |
| const uintptr_t r = _mi_heap_random_next(heap); |
| size_t current = r % slice_count; |
| counts[current]--; |
| mi_block_t* const free_start = blocks[current]; |
| // and iterate through the rest; use `random_shuffle` for performance |
| uintptr_t rnd = _mi_random_shuffle(r|1); // ensure not 0 |
| for (size_t i = 1; i < extend; i++) { |
| // call random_shuffle only every INTPTR_SIZE rounds |
| const size_t round = i%MI_INTPTR_SIZE; |
| if (round == 0) rnd = _mi_random_shuffle(rnd); |
| // select a random next slice index |
| size_t next = ((rnd >> 8*round) & (slice_count-1)); |
| while (counts[next]==0) { // ensure it still has space |
| next++; |
| if (next==slice_count) next = 0; |
| } |
| // and link the current block to it |
| counts[next]--; |
| mi_block_t* const block = blocks[current]; |
| blocks[current] = (mi_block_t*)((uint8_t*)block + bsize); // bump to the following block |
| mi_block_set_next(page, block, blocks[next]); // and set next; note: we may have `current == next` |
| current = next; |
| } |
| // prepend to the free list (usually NULL) |
| mi_block_set_next(page, blocks[current], page->free); // end of the list |
| page->free = free_start; |
| } |
| |
| static mi_decl_noinline void mi_page_free_list_extend( mi_page_t* const page, const size_t bsize, const size_t extend, mi_stats_t* const stats) |
| { |
| MI_UNUSED(stats); |
| #if (MI_SECURE <= 2) |
| mi_assert_internal(page->free == NULL); |
| mi_assert_internal(page->local_free == NULL); |
| #endif |
| mi_assert_internal(page->capacity + extend <= page->reserved); |
| mi_assert_internal(bsize == mi_page_block_size(page)); |
| void* const page_area = _mi_page_start(_mi_page_segment(page), page, NULL ); |
| |
| mi_block_t* const start = mi_page_block_at(page, page_area, bsize, page->capacity); |
| |
| // initialize a sequential free list |
| mi_block_t* const last = mi_page_block_at(page, page_area, bsize, page->capacity + extend - 1); |
| mi_block_t* block = start; |
| while(block <= last) { |
| mi_block_t* next = (mi_block_t*)((uint8_t*)block + bsize); |
| mi_block_set_next(page,block,next); |
| block = next; |
| } |
| // prepend to free list (usually `NULL`) |
| mi_block_set_next(page, last, page->free); |
| page->free = start; |
| } |
| |
| /* ----------------------------------------------------------- |
| Page initialize and extend the capacity |
| ----------------------------------------------------------- */ |
| |
| #define MI_MAX_EXTEND_SIZE (4*1024) // heuristic, one OS page seems to work well. |
| #if (MI_SECURE>0) |
| #define MI_MIN_EXTEND (8*MI_SECURE) // extend at least by this many |
| #else |
| #define MI_MIN_EXTEND (4) |
| #endif |
| |
| // Extend the capacity (up to reserved) by initializing a free list |
| // We do at most `MI_MAX_EXTEND` to avoid touching too much memory |
| // Note: we also experimented with "bump" allocation on the first |
| // allocations but this did not speed up any benchmark (due to an |
| // extra test in malloc? or cache effects?) |
| static void mi_page_extend_free(mi_heap_t* heap, mi_page_t* page, mi_tld_t* tld) { |
| MI_UNUSED(tld); |
| mi_assert_expensive(mi_page_is_valid_init(page)); |
| #if (MI_SECURE<=2) |
| mi_assert(page->free == NULL); |
| mi_assert(page->local_free == NULL); |
| if (page->free != NULL) return; |
| #endif |
| if (page->capacity >= page->reserved) return; |
| |
| size_t page_size; |
| _mi_page_start(_mi_page_segment(page), page, &page_size); |
| mi_stat_counter_increase(tld->stats.pages_extended, 1); |
| |
| // calculate the extend count |
| const size_t bsize = (page->xblock_size < MI_HUGE_BLOCK_SIZE ? page->xblock_size : page_size); |
| size_t extend = page->reserved - page->capacity; |
| mi_assert_internal(extend > 0); |
| |
| size_t max_extend = (bsize >= MI_MAX_EXTEND_SIZE ? MI_MIN_EXTEND : MI_MAX_EXTEND_SIZE/(uint32_t)bsize); |
| if (max_extend < MI_MIN_EXTEND) { max_extend = MI_MIN_EXTEND; } |
| mi_assert_internal(max_extend > 0); |
| |
| if (extend > max_extend) { |
| // ensure we don't touch memory beyond the page to reduce page commit. |
| // the `lean` benchmark tests this. Going from 1 to 8 increases rss by 50%. |
| extend = max_extend; |
| } |
| |
| mi_assert_internal(extend > 0 && extend + page->capacity <= page->reserved); |
| mi_assert_internal(extend < (1UL<<16)); |
| |
| // and append the extend the free list |
| if (extend < MI_MIN_SLICES || MI_SECURE==0) { //!mi_option_is_enabled(mi_option_secure)) { |
| mi_page_free_list_extend(page, bsize, extend, &tld->stats ); |
| } |
| else { |
| mi_page_free_list_extend_secure(heap, page, bsize, extend, &tld->stats); |
| } |
| // enable the new free list |
| page->capacity += (uint16_t)extend; |
| mi_stat_increase(tld->stats.page_committed, extend * bsize); |
| mi_assert_expensive(mi_page_is_valid_init(page)); |
| } |
| |
| // Initialize a fresh page |
| static void mi_page_init(mi_heap_t* heap, mi_page_t* page, size_t block_size, mi_tld_t* tld) { |
| mi_assert(page != NULL); |
| mi_segment_t* segment = _mi_page_segment(page); |
| mi_assert(segment != NULL); |
| mi_assert_internal(block_size > 0); |
| // set fields |
| mi_page_set_heap(page, heap); |
| page->xblock_size = (block_size < MI_HUGE_BLOCK_SIZE ? (uint32_t)block_size : MI_HUGE_BLOCK_SIZE); // initialize before _mi_segment_page_start |
| size_t page_size; |
| const void* page_start = _mi_segment_page_start(segment, page, &page_size); |
| MI_UNUSED(page_start); |
| mi_track_mem_noaccess(page_start,page_size); |
| mi_assert_internal(mi_page_block_size(page) <= page_size); |
| mi_assert_internal(page_size <= page->slice_count*MI_SEGMENT_SLICE_SIZE); |
| mi_assert_internal(page_size / block_size < (1L<<16)); |
| page->reserved = (uint16_t)(page_size / block_size); |
| mi_assert_internal(page->reserved > 0); |
| #if (MI_PADDING || MI_ENCODE_FREELIST) |
| page->keys[0] = _mi_heap_random_next(heap); |
| page->keys[1] = _mi_heap_random_next(heap); |
| #endif |
| page->free_is_zero = page->is_zero_init; |
| #if MI_DEBUG>2 |
| if (page->is_zero_init) { |
| mi_track_mem_defined(page_start, page_size); |
| mi_assert_expensive(mi_mem_is_zero(page_start, page_size)); |
| } |
| #endif |
| |
| mi_assert_internal(page->is_committed); |
| mi_assert_internal(page->capacity == 0); |
| mi_assert_internal(page->free == NULL); |
| mi_assert_internal(page->used == 0); |
| mi_assert_internal(page->xthread_free == 0); |
| mi_assert_internal(page->next == NULL); |
| mi_assert_internal(page->prev == NULL); |
| mi_assert_internal(page->retire_expire == 0); |
| mi_assert_internal(!mi_page_has_aligned(page)); |
| #if (MI_PADDING || MI_ENCODE_FREELIST) |
| mi_assert_internal(page->keys[0] != 0); |
| mi_assert_internal(page->keys[1] != 0); |
| #endif |
| mi_assert_expensive(mi_page_is_valid_init(page)); |
| |
| // initialize an initial free list |
| mi_page_extend_free(heap,page,tld); |
| mi_assert(mi_page_immediate_available(page)); |
| } |
| |
| |
| /* ----------------------------------------------------------- |
| Find pages with free blocks |
| -------------------------------------------------------------*/ |
| |
| // Find a page with free blocks of `page->block_size`. |
| static mi_page_t* mi_page_queue_find_free_ex(mi_heap_t* heap, mi_page_queue_t* pq, bool first_try) |
| { |
| // search through the pages in "next fit" order |
| #if MI_STAT |
| size_t count = 0; |
| #endif |
| mi_page_t* page = pq->first; |
| while (page != NULL) |
| { |
| mi_page_t* next = page->next; // remember next |
| #if MI_STAT |
| count++; |
| #endif |
| |
| // 0. collect freed blocks by us and other threads |
| _mi_page_free_collect(page, false); |
| |
| // 1. if the page contains free blocks, we are done |
| if (mi_page_immediate_available(page)) { |
| break; // pick this one |
| } |
| |
| // 2. Try to extend |
| if (page->capacity < page->reserved) { |
| mi_page_extend_free(heap, page, heap->tld); |
| mi_assert_internal(mi_page_immediate_available(page)); |
| break; |
| } |
| |
| // 3. If the page is completely full, move it to the `mi_pages_full` |
| // queue so we don't visit long-lived pages too often. |
| mi_assert_internal(!mi_page_is_in_full(page) && !mi_page_immediate_available(page)); |
| mi_page_to_full(page, pq); |
| |
| page = next; |
| } // for each page |
| |
| mi_heap_stat_counter_increase(heap, searches, count); |
| |
| if (page == NULL) { |
| _mi_heap_collect_retired(heap, false); // perhaps make a page available? |
| page = mi_page_fresh(heap, pq); |
| if (page == NULL && first_try) { |
| // out-of-memory _or_ an abandoned page with free blocks was reclaimed, try once again |
| page = mi_page_queue_find_free_ex(heap, pq, false); |
| } |
| } |
| else { |
| mi_assert(pq->first == page); |
| page->retire_expire = 0; |
| } |
| mi_assert_internal(page == NULL || mi_page_immediate_available(page)); |
| return page; |
| } |
| |
| |
| |
| // Find a page with free blocks of `size`. |
| static inline mi_page_t* mi_find_free_page(mi_heap_t* heap, size_t size) { |
| mi_page_queue_t* pq = mi_page_queue(heap,size); |
| mi_page_t* page = pq->first; |
| if (page != NULL) { |
| #if (MI_SECURE>=3) // in secure mode, we extend half the time to increase randomness |
| if (page->capacity < page->reserved && ((_mi_heap_random_next(heap) & 1) == 1)) { |
| mi_page_extend_free(heap, page, heap->tld); |
| mi_assert_internal(mi_page_immediate_available(page)); |
| } |
| else |
| #endif |
| { |
| _mi_page_free_collect(page,false); |
| } |
| |
| if (mi_page_immediate_available(page)) { |
| page->retire_expire = 0; |
| return page; // fast path |
| } |
| } |
| return mi_page_queue_find_free_ex(heap, pq, true); |
| } |
| |
| |
| /* ----------------------------------------------------------- |
| Users can register a deferred free function called |
| when the `free` list is empty. Since the `local_free` |
| is separate this is deterministically called after |
| a certain number of allocations. |
| ----------------------------------------------------------- */ |
| |
| static mi_deferred_free_fun* volatile deferred_free = NULL; |
| static _Atomic(void*) deferred_arg; // = NULL |
| |
| void _mi_deferred_free(mi_heap_t* heap, bool force) { |
| heap->tld->heartbeat++; |
| if (deferred_free != NULL && !heap->tld->recurse) { |
| heap->tld->recurse = true; |
| deferred_free(force, heap->tld->heartbeat, mi_atomic_load_ptr_relaxed(void,&deferred_arg)); |
| heap->tld->recurse = false; |
| } |
| } |
| |
| void mi_register_deferred_free(mi_deferred_free_fun* fn, void* arg) mi_attr_noexcept { |
| deferred_free = fn; |
| mi_atomic_store_ptr_release(void,&deferred_arg, arg); |
| } |
| |
| |
| /* ----------------------------------------------------------- |
| General allocation |
| ----------------------------------------------------------- */ |
| |
| // Large and huge page allocation. |
| // Huge pages are allocated directly without being in a queue. |
| // Because huge pages contain just one block, and the segment contains |
| // just that page, we always treat them as abandoned and any thread |
| // that frees the block can free the whole page and segment directly. |
| // Huge pages are also use if the requested alignment is very large (> MI_ALIGNMENT_MAX). |
| static mi_page_t* mi_large_huge_page_alloc(mi_heap_t* heap, size_t size, size_t page_alignment) { |
| size_t block_size = _mi_os_good_alloc_size(size); |
| mi_assert_internal(mi_bin(block_size) == MI_BIN_HUGE || page_alignment > 0); |
| bool is_huge = (block_size > MI_LARGE_OBJ_SIZE_MAX || page_alignment > 0); |
| #if MI_HUGE_PAGE_ABANDON |
| mi_page_queue_t* pq = (is_huge ? NULL : mi_page_queue(heap, block_size)); |
| #else |
| mi_page_queue_t* pq = mi_page_queue(heap, is_huge ? MI_HUGE_BLOCK_SIZE : block_size); // not block_size as that can be low if the page_alignment > 0 |
| mi_assert_internal(!is_huge || mi_page_queue_is_huge(pq)); |
| #endif |
| mi_page_t* page = mi_page_fresh_alloc(heap, pq, block_size, page_alignment); |
| if (page != NULL) { |
| mi_assert_internal(mi_page_immediate_available(page)); |
| |
| if (is_huge) { |
| mi_assert_internal(_mi_page_segment(page)->kind == MI_SEGMENT_HUGE); |
| mi_assert_internal(_mi_page_segment(page)->used==1); |
| #if MI_HUGE_PAGE_ABANDON |
| mi_assert_internal(_mi_page_segment(page)->thread_id==0); // abandoned, not in the huge queue |
| mi_page_set_heap(page, NULL); |
| #endif |
| } |
| else { |
| mi_assert_internal(_mi_page_segment(page)->kind != MI_SEGMENT_HUGE); |
| } |
| |
| const size_t bsize = mi_page_usable_block_size(page); // note: not `mi_page_block_size` to account for padding |
| if (bsize <= MI_LARGE_OBJ_SIZE_MAX) { |
| mi_heap_stat_increase(heap, large, bsize); |
| mi_heap_stat_counter_increase(heap, large_count, 1); |
| } |
| else { |
| mi_heap_stat_increase(heap, huge, bsize); |
| mi_heap_stat_counter_increase(heap, huge_count, 1); |
| } |
| } |
| return page; |
| } |
| |
| |
| // Allocate a page |
| // Note: in debug mode the size includes MI_PADDING_SIZE and might have overflowed. |
| static mi_page_t* mi_find_page(mi_heap_t* heap, size_t size, size_t huge_alignment) mi_attr_noexcept { |
| // huge allocation? |
| const size_t req_size = size - MI_PADDING_SIZE; // correct for padding_size in case of an overflow on `size` |
| if mi_unlikely(req_size > (MI_MEDIUM_OBJ_SIZE_MAX - MI_PADDING_SIZE) || huge_alignment > 0) { |
| if mi_unlikely(req_size > PTRDIFF_MAX) { // we don't allocate more than PTRDIFF_MAX (see <https://sourceware.org/ml/libc-announce/2019/msg00001.html>) |
| _mi_error_message(EOVERFLOW, "allocation request is too large (%zu bytes)\n", req_size); |
| return NULL; |
| } |
| else { |
| return mi_large_huge_page_alloc(heap,size,huge_alignment); |
| } |
| } |
| else { |
| // otherwise find a page with free blocks in our size segregated queues |
| #if MI_PADDING |
| mi_assert_internal(size >= MI_PADDING_SIZE); |
| #endif |
| return mi_find_free_page(heap, size); |
| } |
| } |
| |
| // Generic allocation routine if the fast path (`alloc.c:mi_page_malloc`) does not succeed. |
| // Note: in debug mode the size includes MI_PADDING_SIZE and might have overflowed. |
| // The `huge_alignment` is normally 0 but is set to a multiple of MI_SEGMENT_SIZE for |
| // very large requested alignments in which case we use a huge segment. |
| void* _mi_malloc_generic(mi_heap_t* heap, size_t size, bool zero, size_t huge_alignment) mi_attr_noexcept |
| { |
| mi_assert_internal(heap != NULL); |
| |
| // initialize if necessary |
| if mi_unlikely(!mi_heap_is_initialized(heap)) { |
| heap = mi_heap_get_default(); // calls mi_thread_init |
| if mi_unlikely(!mi_heap_is_initialized(heap)) { return NULL; } |
| } |
| mi_assert_internal(mi_heap_is_initialized(heap)); |
| |
| // call potential deferred free routines |
| _mi_deferred_free(heap, false); |
| |
| // free delayed frees from other threads (but skip contended ones) |
| _mi_heap_delayed_free_partial(heap); |
| |
| // find (or allocate) a page of the right size |
| mi_page_t* page = mi_find_page(heap, size, huge_alignment); |
| if mi_unlikely(page == NULL) { // first time out of memory, try to collect and retry the allocation once more |
| mi_heap_collect(heap, true /* force */); |
| page = mi_find_page(heap, size, huge_alignment); |
| } |
| |
| if mi_unlikely(page == NULL) { // out of memory |
| const size_t req_size = size - MI_PADDING_SIZE; // correct for padding_size in case of an overflow on `size` |
| _mi_error_message(ENOMEM, "unable to allocate memory (%zu bytes)\n", req_size); |
| return NULL; |
| } |
| |
| mi_assert_internal(mi_page_immediate_available(page)); |
| mi_assert_internal(mi_page_block_size(page) >= size); |
| |
| // and try again, this time succeeding! (i.e. this should never recurse through _mi_page_malloc) |
| if mi_unlikely(zero && page->xblock_size == 0) { |
| // note: we cannot call _mi_page_malloc with zeroing for huge blocks; we zero it afterwards in that case. |
| void* p = _mi_page_malloc(heap, page, size, false); |
| mi_assert_internal(p != NULL); |
| _mi_memzero_aligned(p, mi_page_usable_block_size(page)); |
| return p; |
| } |
| else { |
| return _mi_page_malloc(heap, page, size, zero); |
| } |
| } |