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
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
|
/*
* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <AK/Assertions.h>
#include <AK/Memory.h>
#include <Kernel/Heap/SlabAllocator.h>
#include <Kernel/Heap/kmalloc.h>
#include <Kernel/Sections.h>
#include <Kernel/SpinLock.h>
#include <Kernel/VM/Region.h>
#define SANITIZE_SLABS
namespace Kernel {
template<size_t templated_slab_size>
class SlabAllocator {
public:
SlabAllocator() = default;
void init(size_t size)
{
m_base = kmalloc_eternal(size);
m_end = (u8*)m_base + size;
FreeSlab* slabs = (FreeSlab*)m_base;
m_slab_count = size / templated_slab_size;
for (size_t i = 1; i < m_slab_count; ++i) {
slabs[i].next = &slabs[i - 1];
}
slabs[0].next = nullptr;
m_freelist = &slabs[m_slab_count - 1];
m_num_allocated = 0;
}
constexpr size_t slab_size() const { return templated_slab_size; }
size_t slab_count() const { return m_slab_count; }
void* alloc()
{
FreeSlab* free_slab;
{
// We want to avoid being swapped out in the middle of this
ScopedCritical critical;
FreeSlab* next_free;
free_slab = m_freelist.load(AK::memory_order_consume);
do {
if (!free_slab)
return kmalloc(slab_size());
// It's possible another processor is doing the same thing at
// the same time, so next_free *can* be a bogus pointer. However,
// in that case compare_exchange_strong would fail and we would
// try again.
next_free = free_slab->next;
} while (!m_freelist.compare_exchange_strong(free_slab, next_free, AK::memory_order_acq_rel));
m_num_allocated++;
}
#ifdef SANITIZE_SLABS
memset(free_slab, SLAB_ALLOC_SCRUB_BYTE, slab_size());
#endif
return free_slab;
}
void dealloc(void* ptr)
{
VERIFY(ptr);
if (ptr < m_base || ptr >= m_end) {
kfree(ptr);
return;
}
FreeSlab* free_slab = (FreeSlab*)ptr;
#ifdef SANITIZE_SLABS
if (slab_size() > sizeof(FreeSlab*))
memset(free_slab->padding, SLAB_DEALLOC_SCRUB_BYTE, sizeof(FreeSlab::padding));
#endif
// We want to avoid being swapped out in the middle of this
ScopedCritical critical;
FreeSlab* next_free = m_freelist.load(AK::memory_order_consume);
do {
free_slab->next = next_free;
} while (!m_freelist.compare_exchange_strong(next_free, free_slab, AK::memory_order_acq_rel));
m_num_allocated--;
}
size_t num_allocated() const { return m_num_allocated; }
size_t num_free() const { return m_slab_count - m_num_allocated; }
private:
struct FreeSlab {
FreeSlab* next;
char padding[templated_slab_size - sizeof(FreeSlab*)];
};
Atomic<FreeSlab*> m_freelist { nullptr };
Atomic<size_t, AK::MemoryOrder::memory_order_relaxed> m_num_allocated;
size_t m_slab_count;
void* m_base { nullptr };
void* m_end { nullptr };
static_assert(sizeof(FreeSlab) == templated_slab_size);
};
static SlabAllocator<16> s_slab_allocator_16;
static SlabAllocator<32> s_slab_allocator_32;
static SlabAllocator<64> s_slab_allocator_64;
static SlabAllocator<128> s_slab_allocator_128;
static SlabAllocator<256> s_slab_allocator_256;
#if ARCH(I386)
static_assert(sizeof(Region) <= s_slab_allocator_128.slab_size());
#endif
template<typename Callback>
void for_each_allocator(Callback callback)
{
callback(s_slab_allocator_16);
callback(s_slab_allocator_32);
callback(s_slab_allocator_64);
callback(s_slab_allocator_128);
callback(s_slab_allocator_256);
}
UNMAP_AFTER_INIT void slab_alloc_init()
{
s_slab_allocator_16.init(128 * KiB);
s_slab_allocator_32.init(128 * KiB);
s_slab_allocator_64.init(512 * KiB);
s_slab_allocator_128.init(512 * KiB);
s_slab_allocator_256.init(128 * KiB);
}
void* slab_alloc(size_t slab_size)
{
if (slab_size <= 16)
return s_slab_allocator_16.alloc();
if (slab_size <= 32)
return s_slab_allocator_32.alloc();
if (slab_size <= 64)
return s_slab_allocator_64.alloc();
if (slab_size <= 128)
return s_slab_allocator_128.alloc();
if (slab_size <= 256)
return s_slab_allocator_256.alloc();
VERIFY_NOT_REACHED();
}
void slab_dealloc(void* ptr, size_t slab_size)
{
if (slab_size <= 16)
return s_slab_allocator_16.dealloc(ptr);
if (slab_size <= 32)
return s_slab_allocator_32.dealloc(ptr);
if (slab_size <= 64)
return s_slab_allocator_64.dealloc(ptr);
if (slab_size <= 128)
return s_slab_allocator_128.dealloc(ptr);
if (slab_size <= 256)
return s_slab_allocator_256.dealloc(ptr);
VERIFY_NOT_REACHED();
}
void slab_alloc_stats(Function<void(size_t slab_size, size_t allocated, size_t free)> callback)
{
for_each_allocator([&](auto& allocator) {
auto num_allocated = allocator.num_allocated();
auto num_free = allocator.slab_count() - num_allocated;
callback(allocator.slab_size(), num_allocated, num_free);
});
}
}
|
