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/macros.h"
26 #include "base/mutex.h"
27 #include "thread-current-inl.h"
28
29 namespace art {
30
31 // The chunk size by which the swap file is increased and mapped.
32 static constexpr size_t kMininumMapSize = 16 * MB;
33
34 static constexpr bool kCheckFreeMaps = false;
35
36 template <typename FreeBySizeSet>
DumpFreeMap(const FreeBySizeSet & free_by_size)37 static void DumpFreeMap(const FreeBySizeSet& free_by_size) {
38 size_t last_size = static_cast<size_t>(-1);
39 for (const auto& entry : free_by_size) {
40 if (last_size != entry.size) {
41 last_size = entry.size;
42 LOG(INFO) << "Size " << last_size;
43 }
44 LOG(INFO) << " 0x" << std::hex << entry.free_by_start_entry->Start()
45 << " size=" << std::dec << entry.free_by_start_entry->size;
46 }
47 }
48
RemoveChunk(FreeBySizeSet::const_iterator free_by_size_pos)49 void SwapSpace::RemoveChunk(FreeBySizeSet::const_iterator free_by_size_pos) {
50 auto free_by_start_pos = free_by_size_pos->free_by_start_entry;
51 free_by_size_.erase(free_by_size_pos);
52 free_by_start_.erase(free_by_start_pos);
53 }
54
InsertChunk(const SpaceChunk & chunk)55 inline void SwapSpace::InsertChunk(const SpaceChunk& chunk) {
56 DCHECK_NE(chunk.size, 0u);
57 auto insert_result = free_by_start_.insert(chunk);
58 DCHECK(insert_result.second);
59 free_by_size_.emplace(chunk.size, insert_result.first);
60 }
61
SwapSpace(int fd,size_t initial_size)62 SwapSpace::SwapSpace(int fd, size_t initial_size)
63 : fd_(fd),
64 size_(0),
65 lock_("SwapSpace lock", static_cast<LockLevel>(LockLevel::kDefaultMutexLevel - 1)) {
66 // Assume that the file is unlinked.
67
68 InsertChunk(NewFileChunk(initial_size));
69 }
70
~SwapSpace()71 SwapSpace::~SwapSpace() {
72 // Unmap all mmapped chunks. Nothing should be allocated anymore at
73 // this point, so there should be only full size chunks in free_by_start_.
74 for (const SpaceChunk& chunk : free_by_start_) {
75 if (munmap(chunk.ptr, chunk.size) != 0) {
76 PLOG(ERROR) << "Failed to unmap swap space chunk at "
77 << static_cast<const void*>(chunk.ptr) << " size=" << chunk.size;
78 }
79 }
80 // All arenas are backed by the same file. Just close the descriptor.
81 close(fd_);
82 }
83
84 template <typename FreeByStartSet, typename FreeBySizeSet>
CollectFree(const FreeByStartSet & free_by_start,const FreeBySizeSet & free_by_size)85 static size_t CollectFree(const FreeByStartSet& free_by_start, const FreeBySizeSet& free_by_size) {
86 if (free_by_start.size() != free_by_size.size()) {
87 LOG(FATAL) << "Size: " << free_by_start.size() << " vs " << free_by_size.size();
88 }
89
90 // Calculate over free_by_size.
91 size_t sum1 = 0;
92 for (const auto& entry : free_by_size) {
93 sum1 += entry.free_by_start_entry->size;
94 }
95
96 // Calculate over free_by_start.
97 size_t sum2 = 0;
98 for (const auto& entry : free_by_start) {
99 sum2 += entry.size;
100 }
101
102 if (sum1 != sum2) {
103 LOG(FATAL) << "Sum: " << sum1 << " vs " << sum2;
104 }
105 return sum1;
106 }
107
Alloc(size_t size)108 void* SwapSpace::Alloc(size_t size) {
109 MutexLock lock(Thread::Current(), lock_);
110 size = RoundUp(size, 8U);
111
112 // Check the free list for something that fits.
113 // TODO: Smarter implementation. Global biggest chunk, ...
114 auto it = free_by_start_.empty()
115 ? free_by_size_.end()
116 : free_by_size_.lower_bound(FreeBySizeEntry { size, free_by_start_.begin() });
117 if (it != free_by_size_.end()) {
118 SpaceChunk old_chunk = *it->free_by_start_entry;
119 if (old_chunk.size == size) {
120 RemoveChunk(it);
121 } else {
122 // Avoid deallocating and allocating the std::set<> nodes.
123 // This would be much simpler if we could use replace() from Boost.Bimap.
124
125 // The free_by_start_ map contains disjoint intervals ordered by the `ptr`.
126 // Shrinking the interval does not affect the ordering.
127 it->free_by_start_entry->ptr += size;
128 it->free_by_start_entry->size -= size;
129
130 auto node = free_by_size_.extract(it);
131 node.value().size -= size;
132 free_by_size_.insert(std::move(node));
133 }
134 return old_chunk.ptr;
135 } else {
136 // Not a big enough free chunk, need to increase file size.
137 SpaceChunk new_chunk = NewFileChunk(size);
138 if (new_chunk.size != size) {
139 // Insert the remainder.
140 SpaceChunk remainder = { new_chunk.ptr + size, new_chunk.size - size };
141 InsertChunk(remainder);
142 }
143 return new_chunk.ptr;
144 }
145 }
146
NewFileChunk(size_t min_size)147 SwapSpace::SpaceChunk SwapSpace::NewFileChunk(size_t min_size) {
148 #if !defined(__APPLE__)
149 size_t next_part = std::max(RoundUp(min_size, kPageSize), RoundUp(kMininumMapSize, kPageSize));
150 int result = TEMP_FAILURE_RETRY(ftruncate64(fd_, size_ + next_part));
151 if (result != 0) {
152 PLOG(FATAL) << "Unable to increase swap file.";
153 }
154 uint8_t* ptr = reinterpret_cast<uint8_t*>(
155 mmap(nullptr, next_part, PROT_READ | PROT_WRITE, MAP_SHARED, fd_, size_));
156 if (ptr == MAP_FAILED) {
157 LOG(ERROR) << "Unable to mmap new swap file chunk.";
158 LOG(ERROR) << "Current size: " << size_ << " requested: " << next_part << "/" << min_size;
159 LOG(ERROR) << "Free list:";
160 DumpFreeMap(free_by_size_);
161 LOG(ERROR) << "In free list: " << CollectFree(free_by_start_, free_by_size_);
162 LOG(FATAL) << "Aborting...";
163 }
164 size_ += next_part;
165 SpaceChunk new_chunk = {ptr, next_part};
166 return new_chunk;
167 #else
168 UNUSED(min_size, kMininumMapSize);
169 LOG(FATAL) << "No swap file support on the Mac.";
170 UNREACHABLE();
171 #endif
172 }
173
174 // TODO: Full coalescing.
Free(void * ptr,size_t size)175 void SwapSpace::Free(void* ptr, size_t size) {
176 MutexLock lock(Thread::Current(), lock_);
177 size = RoundUp(size, 8U);
178
179 size_t free_before = 0;
180 if (kCheckFreeMaps) {
181 free_before = CollectFree(free_by_start_, free_by_size_);
182 }
183
184 SpaceChunk chunk = { reinterpret_cast<uint8_t*>(ptr), size };
185 auto it = free_by_start_.lower_bound(chunk);
186 if (it != free_by_start_.begin()) {
187 auto prev = it;
188 --prev;
189 CHECK_LE(prev->End(), chunk.Start());
190 if (prev->End() == chunk.Start()) {
191 // Merge *prev with this chunk.
192 chunk.size += prev->size;
193 chunk.ptr -= prev->size;
194 auto erase_pos = free_by_size_.find(FreeBySizeEntry { prev->size, prev });
195 DCHECK(erase_pos != free_by_size_.end());
196 RemoveChunk(erase_pos);
197 // "prev" is invalidated but "it" remains valid.
198 }
199 }
200 if (it != free_by_start_.end()) {
201 CHECK_LE(chunk.End(), it->Start());
202 if (chunk.End() == it->Start()) {
203 // Merge *it with this chunk.
204 chunk.size += it->size;
205 auto erase_pos = free_by_size_.find(FreeBySizeEntry { it->size, it });
206 DCHECK(erase_pos != free_by_size_.end());
207 RemoveChunk(erase_pos);
208 // "it" is invalidated but we don't need it anymore.
209 }
210 }
211 InsertChunk(chunk);
212
213 if (kCheckFreeMaps) {
214 size_t free_after = CollectFree(free_by_start_, free_by_size_);
215
216 if (free_after != free_before + size) {
217 DumpFreeMap(free_by_size_);
218 CHECK_EQ(free_after, free_before + size) << "Should be " << size << " difference from " << free_before;
219 }
220 }
221 }
222
223 } // namespace art
224