1 /*
2 * Copyright (C) 2014 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17 #include "swap_space.h"
18
19 #include <sys/mman.h>
20
21 #include <algorithm>
22 #include <numeric>
23
24 #include "base/bit_utils.h"
25 #include "base/mem_map.h"
26 #include "base/macros.h"
27 #include "base/mutex.h"
28 #include "thread-current-inl.h"
29
30 namespace art {
31
32 // The chunk size by which the swap file is increased and mapped.
33 static constexpr size_t kMinimumMapSize = 16 * MB;
34
35 static constexpr bool kCheckFreeMaps = false;
36
37 template <typename FreeBySizeSet>
DumpFreeMap(const FreeBySizeSet & free_by_size)38 static void DumpFreeMap(const FreeBySizeSet& free_by_size) {
39 size_t last_size = static_cast<size_t>(-1);
40 for (const auto& entry : free_by_size) {
41 if (last_size != entry.size) {
42 last_size = entry.size;
43 LOG(INFO) << "Size " << last_size;
44 }
45 LOG(INFO) << " 0x" << std::hex << entry.free_by_start_entry->Start()
46 << " size=" << std::dec << entry.free_by_start_entry->size;
47 }
48 }
49
RemoveChunk(FreeBySizeSet::const_iterator free_by_size_pos)50 void SwapSpace::RemoveChunk(FreeBySizeSet::const_iterator free_by_size_pos) {
51 auto free_by_start_pos = free_by_size_pos->free_by_start_entry;
52 free_by_size_.erase(free_by_size_pos);
53 free_by_start_.erase(free_by_start_pos);
54 }
55
InsertChunk(const SpaceChunk & chunk)56 inline void SwapSpace::InsertChunk(const SpaceChunk& chunk) {
57 DCHECK_NE(chunk.size, 0u);
58 auto insert_result = free_by_start_.insert(chunk);
59 DCHECK(insert_result.second);
60 free_by_size_.emplace(chunk.size, insert_result.first);
61 }
62
SwapSpace(int fd,size_t initial_size)63 SwapSpace::SwapSpace(int fd, size_t initial_size)
64 : fd_(fd),
65 size_(0),
66 lock_("SwapSpace lock", static_cast<LockLevel>(LockLevel::kDefaultMutexLevel - 1)) {
67 // Assume that the file is unlinked.
68
69 InsertChunk(NewFileChunk(initial_size));
70 }
71
~SwapSpace()72 SwapSpace::~SwapSpace() {
73 // Unmap all mmapped chunks. Nothing should be allocated anymore at
74 // this point, so there should be only full size chunks in free_by_start_.
75 for (const SpaceChunk& chunk : free_by_start_) {
76 if (munmap(chunk.ptr, chunk.size) != 0) {
77 PLOG(ERROR) << "Failed to unmap swap space chunk at "
78 << static_cast<const void*>(chunk.ptr) << " size=" << chunk.size;
79 }
80 }
81 // All arenas are backed by the same file. Just close the descriptor.
82 close(fd_);
83 }
84
85 template <typename FreeByStartSet, typename FreeBySizeSet>
CollectFree(const FreeByStartSet & free_by_start,const FreeBySizeSet & free_by_size)86 static size_t CollectFree(const FreeByStartSet& free_by_start, const FreeBySizeSet& free_by_size) {
87 if (free_by_start.size() != free_by_size.size()) {
88 LOG(FATAL) << "Size: " << free_by_start.size() << " vs " << free_by_size.size();
89 }
90
91 // Calculate over free_by_size.
92 size_t sum1 = 0;
93 for (const auto& entry : free_by_size) {
94 sum1 += entry.free_by_start_entry->size;
95 }
96
97 // Calculate over free_by_start.
98 size_t sum2 = 0;
99 for (const auto& entry : free_by_start) {
100 sum2 += entry.size;
101 }
102
103 if (sum1 != sum2) {
104 LOG(FATAL) << "Sum: " << sum1 << " vs " << sum2;
105 }
106 return sum1;
107 }
108
Alloc(size_t size)109 void* SwapSpace::Alloc(size_t size) {
110 MutexLock lock(Thread::Current(), lock_);
111 size = RoundUp(size, 8U);
112
113 // Check the free list for something that fits.
114 // TODO: Smarter implementation. Global biggest chunk, ...
115 auto it = free_by_start_.empty()
116 ? free_by_size_.end()
117 : free_by_size_.lower_bound(FreeBySizeEntry { size, free_by_start_.begin() });
118 if (it != free_by_size_.end()) {
119 SpaceChunk old_chunk = *it->free_by_start_entry;
120 if (old_chunk.size == size) {
121 RemoveChunk(it);
122 } else {
123 // Avoid deallocating and allocating the std::set<> nodes.
124 // This would be much simpler if we could use replace() from Boost.Bimap.
125
126 // The free_by_start_ map contains disjoint intervals ordered by the `ptr`.
127 // Shrinking the interval does not affect the ordering.
128 it->free_by_start_entry->ptr += size;
129 it->free_by_start_entry->size -= size;
130
131 auto node = free_by_size_.extract(it);
132 node.value().size -= size;
133 free_by_size_.insert(std::move(node));
134 }
135 return old_chunk.ptr;
136 } else {
137 // Not a big enough free chunk, need to increase file size.
138 SpaceChunk new_chunk = NewFileChunk(size);
139 if (new_chunk.size != size) {
140 // Insert the remainder.
141 SpaceChunk remainder = { new_chunk.ptr + size, new_chunk.size - size };
142 InsertChunk(remainder);
143 }
144 return new_chunk.ptr;
145 }
146 }
147
NewFileChunk(size_t min_size)148 SwapSpace::SpaceChunk SwapSpace::NewFileChunk(size_t min_size) {
149 #if !defined(__APPLE__)
150 const size_t page_size = MemMap::GetPageSize();
151 size_t next_part = std::max(RoundUp(min_size, page_size), RoundUp(kMinimumMapSize, page_size));
152 int result = TEMP_FAILURE_RETRY(ftruncate64(fd_, size_ + next_part));
153 if (result != 0) {
154 PLOG(FATAL) << "Unable to increase swap file.";
155 }
156 uint8_t* ptr = reinterpret_cast<uint8_t*>(
157 mmap(nullptr, next_part, PROT_READ | PROT_WRITE, MAP_SHARED, fd_, size_));
158 if (ptr == MAP_FAILED) {
159 LOG(ERROR) << "Unable to mmap new swap file chunk.";
160 LOG(ERROR) << "Current size: " << size_ << " requested: " << next_part << "/" << min_size;
161 LOG(ERROR) << "Free list:";
162 DumpFreeMap(free_by_size_);
163 LOG(ERROR) << "In free list: " << CollectFree(free_by_start_, free_by_size_);
164 PLOG(FATAL) << "Unable to mmap new swap file chunk.";
165 }
166 size_ += next_part;
167 SpaceChunk new_chunk = {ptr, next_part};
168 return new_chunk;
169 #else
170 UNUSED(min_size, kMinimumMapSize);
171 LOG(FATAL) << "No swap file support on the Mac.";
172 UNREACHABLE();
173 #endif
174 }
175
176 // TODO: Full coalescing.
Free(void * ptr,size_t size)177 void SwapSpace::Free(void* ptr, size_t size) {
178 MutexLock lock(Thread::Current(), lock_);
179 size = RoundUp(size, 8U);
180
181 size_t free_before = 0;
182 if (kCheckFreeMaps) {
183 free_before = CollectFree(free_by_start_, free_by_size_);
184 }
185
186 SpaceChunk chunk = { reinterpret_cast<uint8_t*>(ptr), size };
187 auto it = free_by_start_.lower_bound(chunk);
188 if (it != free_by_start_.begin()) {
189 auto prev = it;
190 --prev;
191 CHECK_LE(prev->End(), chunk.Start());
192 if (prev->End() == chunk.Start()) {
193 // Merge *prev with this chunk.
194 chunk.size += prev->size;
195 chunk.ptr -= prev->size;
196 auto erase_pos = free_by_size_.find(FreeBySizeEntry { prev->size, prev });
197 DCHECK(erase_pos != free_by_size_.end());
198 RemoveChunk(erase_pos);
199 // "prev" is invalidated but "it" remains valid.
200 }
201 }
202 if (it != free_by_start_.end()) {
203 CHECK_LE(chunk.End(), it->Start());
204 if (chunk.End() == it->Start()) {
205 // Merge *it with this chunk.
206 chunk.size += it->size;
207 auto erase_pos = free_by_size_.find(FreeBySizeEntry { it->size, it });
208 DCHECK(erase_pos != free_by_size_.end());
209 RemoveChunk(erase_pos);
210 // "it" is invalidated but we don't need it anymore.
211 }
212 }
213 InsertChunk(chunk);
214
215 if (kCheckFreeMaps) {
216 size_t free_after = CollectFree(free_by_start_, free_by_size_);
217
218 if (free_after != free_before + size) {
219 DumpFreeMap(free_by_size_);
220 CHECK_EQ(free_after, free_before + size) << "Should be " << size << " difference from " << free_before;
221 }
222 }
223 }
224
225 } // namespace art
226