1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
|
/* ----------------------------------------------------------------------------
Copyright (c) 2019-2023, 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 following functions are to reliably find the segment or
block that encompasses any pointer p (or NULL if it is not
in any of our segments).
We maintain a bitmap of all memory with 1 bit per MI_SEGMENT_SIZE (64MiB)
set to 1 if it contains the segment meta data.
----------------------------------------------------------- */
#include "mimalloc.h"
#include "mimalloc/internal.h"
#include "mimalloc/atomic.h"
#if (MI_INTPTR_SIZE==8)
#define MI_MAX_ADDRESS ((size_t)40 << 40) // 40TB (to include huge page areas)
#else
#define MI_MAX_ADDRESS ((size_t)2 << 30) // 2Gb
#endif
#define MI_SEGMENT_MAP_BITS (MI_MAX_ADDRESS / MI_SEGMENT_SIZE)
#define MI_SEGMENT_MAP_SIZE (MI_SEGMENT_MAP_BITS / 8)
#define MI_SEGMENT_MAP_WSIZE (MI_SEGMENT_MAP_SIZE / MI_INTPTR_SIZE)
static _Atomic(uintptr_t) mi_segment_map[MI_SEGMENT_MAP_WSIZE + 1]; // 2KiB per TB with 64MiB segments
static size_t mi_segment_map_index_of(const mi_segment_t* segment, size_t* bitidx) {
mi_assert_internal(_mi_ptr_segment(segment + 1) == segment); // is it aligned on MI_SEGMENT_SIZE?
if ((uintptr_t)segment >= MI_MAX_ADDRESS) {
*bitidx = 0;
return MI_SEGMENT_MAP_WSIZE;
}
else {
const uintptr_t segindex = ((uintptr_t)segment) / MI_SEGMENT_SIZE;
*bitidx = segindex % MI_INTPTR_BITS;
const size_t mapindex = segindex / MI_INTPTR_BITS;
mi_assert_internal(mapindex < MI_SEGMENT_MAP_WSIZE);
return mapindex;
}
}
void _mi_segment_map_allocated_at(const mi_segment_t* segment) {
size_t bitidx;
size_t index = mi_segment_map_index_of(segment, &bitidx);
mi_assert_internal(index <= MI_SEGMENT_MAP_WSIZE);
if (index==MI_SEGMENT_MAP_WSIZE) return;
uintptr_t mask = mi_atomic_load_relaxed(&mi_segment_map[index]);
uintptr_t newmask;
do {
newmask = (mask | ((uintptr_t)1 << bitidx));
} while (!mi_atomic_cas_weak_release(&mi_segment_map[index], &mask, newmask));
}
void _mi_segment_map_freed_at(const mi_segment_t* segment) {
size_t bitidx;
size_t index = mi_segment_map_index_of(segment, &bitidx);
mi_assert_internal(index <= MI_SEGMENT_MAP_WSIZE);
if (index == MI_SEGMENT_MAP_WSIZE) return;
uintptr_t mask = mi_atomic_load_relaxed(&mi_segment_map[index]);
uintptr_t newmask;
do {
newmask = (mask & ~((uintptr_t)1 << bitidx));
} while (!mi_atomic_cas_weak_release(&mi_segment_map[index], &mask, newmask));
}
// Determine the segment belonging to a pointer or NULL if it is not in a valid segment.
static mi_segment_t* _mi_segment_of(const void* p) {
if (p == NULL) return NULL;
mi_segment_t* segment = _mi_ptr_segment(p);
mi_assert_internal(segment != NULL);
size_t bitidx;
size_t index = mi_segment_map_index_of(segment, &bitidx);
// fast path: for any pointer to valid small/medium/large object or first MI_SEGMENT_SIZE in huge
const uintptr_t mask = mi_atomic_load_relaxed(&mi_segment_map[index]);
if mi_likely((mask & ((uintptr_t)1 << bitidx)) != 0) {
return segment; // yes, allocated by us
}
if (index==MI_SEGMENT_MAP_WSIZE) return NULL;
// TODO: maintain max/min allocated range for efficiency for more efficient rejection of invalid pointers?
// search downwards for the first segment in case it is an interior pointer
// could be slow but searches in MI_INTPTR_SIZE * MI_SEGMENT_SIZE (512MiB) steps trough
// valid huge objects
// note: we could maintain a lowest index to speed up the path for invalid pointers?
size_t lobitidx;
size_t loindex;
uintptr_t lobits = mask & (((uintptr_t)1 << bitidx) - 1);
if (lobits != 0) {
loindex = index;
lobitidx = mi_bsr(lobits); // lobits != 0
}
else if (index == 0) {
return NULL;
}
else {
mi_assert_internal(index > 0);
uintptr_t lomask = mask;
loindex = index;
do {
loindex--;
lomask = mi_atomic_load_relaxed(&mi_segment_map[loindex]);
} while (lomask != 0 && loindex > 0);
if (lomask == 0) return NULL;
lobitidx = mi_bsr(lomask); // lomask != 0
}
mi_assert_internal(loindex < MI_SEGMENT_MAP_WSIZE);
// take difference as the addresses could be larger than the MAX_ADDRESS space.
size_t diff = (((index - loindex) * (8*MI_INTPTR_SIZE)) + bitidx - lobitidx) * MI_SEGMENT_SIZE;
segment = (mi_segment_t*)((uint8_t*)segment - diff);
if (segment == NULL) return NULL;
mi_assert_internal((void*)segment < p);
bool cookie_ok = (_mi_ptr_cookie(segment) == segment->cookie);
mi_assert_internal(cookie_ok);
if mi_unlikely(!cookie_ok) return NULL;
if (((uint8_t*)segment + mi_segment_size(segment)) <= (uint8_t*)p) return NULL; // outside the range
mi_assert_internal(p >= (void*)segment && (uint8_t*)p < (uint8_t*)segment + mi_segment_size(segment));
return segment;
}
// Is this a valid pointer in our heap?
static bool mi_is_valid_pointer(const void* p) {
return ((_mi_segment_of(p) != NULL) || (_mi_arena_contains(p)));
}
mi_decl_nodiscard mi_decl_export bool mi_is_in_heap_region(const void* p) mi_attr_noexcept {
return mi_is_valid_pointer(p);
}
/*
// Return the full segment range belonging to a pointer
static void* mi_segment_range_of(const void* p, size_t* size) {
mi_segment_t* segment = _mi_segment_of(p);
if (segment == NULL) {
if (size != NULL) *size = 0;
return NULL;
}
else {
if (size != NULL) *size = segment->segment_size;
return segment;
}
mi_assert_expensive(page == NULL || mi_segment_is_valid(_mi_page_segment(page),tld));
mi_assert_internal(page == NULL || (mi_segment_page_size(_mi_page_segment(page)) - (MI_SECURE == 0 ? 0 : _mi_os_page_size())) >= block_size);
mi_reset_delayed(tld);
mi_assert_internal(page == NULL || mi_page_not_in_queue(page, tld));
return page;
}
*/
|
