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commit 2level page-map on over-commit systems

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daanx 2024-12-23 09:53:52 -08:00
parent bc5ae31649
commit 657135de36
4 changed files with 26 additions and 23 deletions
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26
include/mimalloc/internal.h
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@ -435,13 +435,14 @@ static inline mi_page_t* _mi_heap_get_free_small_page(mi_heap_t* heap, size_t si
/* -----------------------------------------------------------
Pages
The page map maps addresses to `mi_page_t` pointers
----------------------------------------------------------- */
#if MI_PAGE_MAP_FLAT
// flat page-map committed on demand
// flat page-map committed on demand, using one byte per slice (64 KiB).
// single indirection and low commit, but large initial virtual reserve (4 GiB with 48 bit virtual addresses)
// used by default on <= 40 bit virtual address spaces.
extern uint8_t* _mi_page_map;
static inline size_t _mi_page_map_index(const void* p) {
@ -468,26 +469,23 @@ static inline mi_page_t* _mi_unchecked_ptr_page(const void* p) {
#else
// 2-level page map:
// double indirection but low commit and low virtual reserve.
//
// The page-map is usually 4 MiB and points to sub maps of 64 KiB.
// The page-map is committed on-demand (in 64 KiB) parts (and sub-maps are committed on-demand as well)
// One sub page-map = 64 KiB => covers 2^13 * 2^16 = 2^32 = 512 MiB address space
// The page-map needs 48-16-13 = 19 bits => 2^19 sub map pointers = 4 MiB size.
// (Choosing a MI_PAGE_MAP_SUB_SHIFT of 16 gives slightly better code but will commit the initial sub-map at 512 KiB)
// double indirection, but low commit and low virtual reserve.
//
// the page-map is usually 4 MiB and points to sub maps of 64 KiB.
// the page-map is committed on-demand (in 64 KiB parts) (and sub-maps are committed on-demand as well)
// one sub page-map = 64 KiB => covers 2^(16-3) * 2^16 = 2^29 = 512 MiB address space
// the page-map needs 48-(16+13) = 19 bits => 2^19 sub map pointers = 4 MiB size.
#define MI_PAGE_MAP_SUB_SHIFT (13)
#define MI_PAGE_MAP_SUB_COUNT (MI_ZU(1) << MI_PAGE_MAP_SUB_SHIFT)
#define MI_PAGE_MAP_SHIFT (MI_MAX_VABITS - MI_PAGE_MAP_SUB_SHIFT - MI_ARENA_SLICE_SHIFT)
#define MI_PAGE_MAP_COUNT (MI_ZU(1) << MI_PAGE_MAP_SHIFT)
extern mi_page_t*** _mi_page_map;
static inline size_t _mi_page_map_index(const void* p, size_t* sub_idx) {
const uintptr_t u = (uintptr_t)p / MI_ARENA_SLICE_SIZE;
if (sub_idx != NULL) { *sub_idx = (uint32_t)u % MI_PAGE_MAP_SUB_COUNT; }
return (size_t)(u / MI_PAGE_MAP_SUB_COUNT);
const size_t u = (size_t)((uintptr_t)p / MI_ARENA_SLICE_SIZE);
if (sub_idx != NULL) { *sub_idx = u % MI_PAGE_MAP_SUB_COUNT; }
return (u / MI_PAGE_MAP_SUB_COUNT);
}
static inline mi_page_t* _mi_unchecked_ptr_page(const void* p) {