mimalloc/src/page-queue.c

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/*----------------------------------------------------------------------------
Copyright (c) 2018-2020, Microsoft Research, Daan Leijen
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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.
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-----------------------------------------------------------------------------*/
/* -----------------------------------------------------------
Definition of page queues for each block size
----------------------------------------------------------- */
#ifndef MI_IN_PAGE_C
#error "this file should be included from 'page.c'"
#endif
/* -----------------------------------------------------------
Minimal alignment in machine words (i.e. `sizeof(void*)`)
----------------------------------------------------------- */
#if (MI_MAX_ALIGN_SIZE > 4*MI_INTPTR_SIZE)
#error "define alignment for more than 4x word size for this platform"
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#elif (MI_MAX_ALIGN_SIZE > 2*MI_INTPTR_SIZE)
#define MI_ALIGN4W // 4 machine words minimal alignment
#elif (MI_MAX_ALIGN_SIZE > MI_INTPTR_SIZE)
#define MI_ALIGN2W // 2 machine words minimal alignment
#else
// ok, default alignment is 1 word
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#endif
/* -----------------------------------------------------------
Queue query
----------------------------------------------------------- */
static inline bool mi_page_queue_is_huge(const mi_page_queue_t* pq) {
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return (pq->block_size == (MI_MEDIUM_OBJ_SIZE_MAX+sizeof(uintptr_t)));
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}
static inline bool mi_page_queue_is_full(const mi_page_queue_t* pq) {
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return (pq->block_size == (MI_MEDIUM_OBJ_SIZE_MAX+(2*sizeof(uintptr_t))));
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}
static inline bool mi_page_queue_is_special(const mi_page_queue_t* pq) {
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return (pq->block_size > MI_MEDIUM_OBJ_SIZE_MAX);
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}
/* -----------------------------------------------------------
Bins
----------------------------------------------------------- */
// Return the bin for a given field size.
// Returns MI_BIN_HUGE if the size is too large.
// We use `wsize` for the size in "machine word sizes",
// i.e. byte size == `wsize*sizeof(void*)`.
extern inline uint8_t _mi_bin(size_t size) {
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size_t wsize = _mi_wsize_from_size(size);
uint8_t bin;
if (wsize <= 1) {
bin = 1;
}
#if defined(MI_ALIGN4W)
else if (wsize <= 4) {
bin = (uint8_t)((wsize+1)&~1); // round to double word sizes
}
#elif defined(MI_ALIGN2W)
else if (wsize <= 8) {
bin = (uint8_t)((wsize+1)&~1); // round to double word sizes
}
#else
else if (wsize <= 8) {
bin = (uint8_t)wsize;
}
#endif
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else if (wsize > MI_MEDIUM_OBJ_WSIZE_MAX) {
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bin = MI_BIN_HUGE;
}
else {
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#if defined(MI_ALIGN4W)
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if (wsize <= 16) { wsize = (wsize+3)&~3; } // round to 4x word sizes
#endif
wsize--;
// find the highest bit
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uint8_t b = (uint8_t)mi_bsr(wsize); // note: wsize != 0
// and use the top 3 bits to determine the bin (~12.5% worst internal fragmentation).
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// - adjust with 3 because we use do not round the first 8 sizes
// which each get an exact bin
bin = ((b << 2) + (uint8_t)((wsize >> (b - 2)) & 0x03)) - 3;
mi_assert_internal(bin < MI_BIN_HUGE);
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}
mi_assert_internal(bin > 0 && bin <= MI_BIN_HUGE);
return bin;
}
/* -----------------------------------------------------------
Queue of pages with free blocks
----------------------------------------------------------- */
size_t _mi_bin_size(uint8_t bin) {
return _mi_heap_empty.pages[bin].block_size;
}
// Good size for allocation
size_t mi_good_size(size_t size) mi_attr_noexcept {
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if (size <= MI_MEDIUM_OBJ_SIZE_MAX) {
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return _mi_bin_size(_mi_bin(size));
}
else {
return _mi_align_up(size,_mi_os_page_size());
}
}
#if (MI_DEBUG>1)
static bool mi_page_queue_contains(mi_page_queue_t* queue, const mi_page_t* page) {
mi_assert_internal(page != NULL);
mi_page_t* list = queue->first;
while (list != NULL) {
mi_assert_internal(list->next == NULL || list->next->prev == list);
mi_assert_internal(list->prev == NULL || list->prev->next == list);
if (list == page) break;
list = list->next;
}
return (list == page);
}
#endif
#if (MI_DEBUG>1)
static bool mi_heap_contains_queue(const mi_heap_t* heap, const mi_page_queue_t* pq) {
return (pq >= &heap->pages[0] && pq <= &heap->pages[MI_BIN_FULL]);
}
#endif
static mi_page_queue_t* mi_page_queue_of(const mi_page_t* page) {
uint8_t bin = (mi_page_is_in_full(page) ? MI_BIN_FULL : _mi_bin(page->xblock_size));
mi_heap_t* heap = mi_page_heap(page);
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mi_assert_internal(heap != NULL && bin <= MI_BIN_FULL);
mi_page_queue_t* pq = &heap->pages[bin];
mi_assert_internal(bin >= MI_BIN_HUGE || page->xblock_size == pq->block_size);
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mi_assert_expensive(mi_page_queue_contains(pq, page));
return pq;
}
static mi_page_queue_t* mi_heap_page_queue_of(mi_heap_t* heap, const mi_page_t* page) {
uint8_t bin = (mi_page_is_in_full(page) ? MI_BIN_FULL : _mi_bin(page->xblock_size));
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mi_assert_internal(bin <= MI_BIN_FULL);
mi_page_queue_t* pq = &heap->pages[bin];
mi_assert_internal(mi_page_is_in_full(page) || page->xblock_size == pq->block_size);
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return pq;
}
// The current small page array is for efficiency and for each
// small size (up to 256) it points directly to the page for that
// size without having to compute the bin. This means when the
// current free page queue is updated for a small bin, we need to update a
// range of entries in `_mi_page_small_free`.
static inline void mi_heap_queue_first_update(mi_heap_t* heap, const mi_page_queue_t* pq) {
mi_assert_internal(mi_heap_contains_queue(heap,pq));
size_t size = pq->block_size;
if (size > MI_SMALL_SIZE_MAX) return;
mi_page_t* page = pq->first;
if (pq->first == NULL) page = (mi_page_t*)&_mi_page_empty;
// find index in the right direct page array
size_t start;
size_t idx = _mi_wsize_from_size(size);
mi_page_t** pages_free = heap->pages_free_direct;
if (pages_free[idx] == page) return; // already set
// find start slot
if (idx<=1) {
start = 0;
}
else {
// find previous size; due to minimal alignment upto 3 previous bins may need to be skipped
uint8_t bin = _mi_bin(size);
const mi_page_queue_t* prev = pq - 1;
while( bin == _mi_bin(prev->block_size) && prev > &heap->pages[0]) {
prev--;
}
start = 1 + _mi_wsize_from_size(prev->block_size);
if (start > idx) start = idx;
}
// set size range to the right page
mi_assert(start <= idx);
for (size_t sz = start; sz <= idx; sz++) {
pages_free[sz] = page;
}
}
/*
static bool mi_page_queue_is_empty(mi_page_queue_t* queue) {
return (queue->first == NULL);
}
*/
static void mi_page_queue_remove(mi_page_queue_t* queue, mi_page_t* page) {
mi_assert_internal(page != NULL);
mi_assert_expensive(mi_page_queue_contains(queue, page));
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mi_assert_internal(page->xblock_size == queue->block_size || (page->xblock_size > MI_MEDIUM_OBJ_SIZE_MAX && mi_page_queue_is_huge(queue)) || (mi_page_is_in_full(page) && mi_page_queue_is_full(queue)));
mi_heap_t* heap = mi_page_heap(page);
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if (page->prev != NULL) page->prev->next = page->next;
if (page->next != NULL) page->next->prev = page->prev;
if (page == queue->last) queue->last = page->prev;
if (page == queue->first) {
queue->first = page->next;
// update first
mi_assert_internal(mi_heap_contains_queue(heap, queue));
mi_heap_queue_first_update(heap,queue);
}
heap->page_count--;
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page->next = NULL;
page->prev = NULL;
// mi_atomic_store_ptr_release(mi_atomic_cast(void*, &page->heap), NULL);
mi_page_set_in_full(page,false);
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}
static void mi_page_queue_push(mi_heap_t* heap, mi_page_queue_t* queue, mi_page_t* page) {
mi_assert_internal(mi_page_heap(page) == heap);
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mi_assert_internal(!mi_page_queue_contains(queue, page));
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mi_assert_internal(_mi_page_segment(page)->kind != MI_SEGMENT_HUGE);
mi_assert_internal(page->xblock_size == queue->block_size ||
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(page->xblock_size > MI_MEDIUM_OBJ_SIZE_MAX) ||
(mi_page_is_in_full(page) && mi_page_queue_is_full(queue)));
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mi_page_set_in_full(page, mi_page_queue_is_full(queue));
// mi_atomic_store_ptr_release(mi_atomic_cast(void*, &page->heap), heap);
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page->next = queue->first;
page->prev = NULL;
if (queue->first != NULL) {
mi_assert_internal(queue->first->prev == NULL);
queue->first->prev = page;
queue->first = page;
}
else {
queue->first = queue->last = page;
}
// update direct
mi_heap_queue_first_update(heap, queue);
heap->page_count++;
}
static void mi_page_queue_enqueue_from(mi_page_queue_t* to, mi_page_queue_t* from, mi_page_t* page) {
mi_assert_internal(page != NULL);
mi_assert_expensive(mi_page_queue_contains(from, page));
mi_assert_expensive(!mi_page_queue_contains(to, page));
mi_assert_internal((page->xblock_size == to->block_size && page->xblock_size == from->block_size) ||
(page->xblock_size == to->block_size && mi_page_queue_is_full(from)) ||
(page->xblock_size == from->block_size && mi_page_queue_is_full(to)) ||
(page->xblock_size > MI_LARGE_OBJ_SIZE_MAX && mi_page_queue_is_huge(to)) ||
(page->xblock_size > MI_LARGE_OBJ_SIZE_MAX && mi_page_queue_is_full(to)));
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mi_heap_t* heap = mi_page_heap(page);
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if (page->prev != NULL) page->prev->next = page->next;
if (page->next != NULL) page->next->prev = page->prev;
if (page == from->last) from->last = page->prev;
if (page == from->first) {
from->first = page->next;
// update first
mi_assert_internal(mi_heap_contains_queue(heap, from));
mi_heap_queue_first_update(heap, from);
}
page->prev = to->last;
page->next = NULL;
if (to->last != NULL) {
mi_assert_internal(heap == mi_page_heap(to->last));
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to->last->next = page;
to->last = page;
}
else {
to->first = page;
to->last = page;
mi_heap_queue_first_update(heap, to);
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}
mi_page_set_in_full(page, mi_page_queue_is_full(to));
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}
// Only called from `mi_heap_absorb`.
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size_t _mi_page_queue_append(mi_heap_t* heap, mi_page_queue_t* pq, mi_page_queue_t* append) {
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mi_assert_internal(mi_heap_contains_queue(heap,pq));
mi_assert_internal(pq->block_size == append->block_size);
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if (append->first==NULL) return 0;
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// set append pages to new heap and count
size_t count = 0;
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for (mi_page_t* page = append->first; page != NULL; page = page->next) {
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// inline `mi_page_set_heap` to avoid wrong assertion during absorption;
// in this case it is ok to be delayed freeing since both "to" and "from" heap are still alive.
mi_atomic_store_release(&page->xheap, (uintptr_t)heap);
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// set the flag to delayed free (not overriding NEVER_DELAYED_FREE) which has as a
// side effect that it spins until any DELAYED_FREEING is finished. This ensures
// that after appending only the new heap will be used for delayed free operations.
_mi_page_use_delayed_free(page, MI_USE_DELAYED_FREE, false);
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count++;
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}
if (pq->last==NULL) {
// take over afresh
mi_assert_internal(pq->first==NULL);
pq->first = append->first;
pq->last = append->last;
mi_heap_queue_first_update(heap, pq);
}
else {
// append to end
mi_assert_internal(pq->last!=NULL);
mi_assert_internal(append->first!=NULL);
pq->last->next = append->first;
append->first->prev = pq->last;
pq->last = append->last;
}
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return count;
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}