lockedpool.cpp raw
1 // Copyright (c) 2016-present The Bitcoin Core developers
2 // Distributed under the MIT software license, see the accompanying
3 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
4
5 #include <support/lockedpool.h>
6 #include <support/cleanse.h>
7
8 #ifdef WIN32
9 #include <windows.h>
10 #else
11 #include <sys/mman.h>
12 #include <sys/resource.h>
13 #include <unistd.h>
14 #endif
15
16 #include <algorithm>
17 #include <limits>
18 #include <stdexcept>
19 #include <utility>
20 #ifdef ARENA_DEBUG
21 #include <iomanip>
22 #include <iostream>
23 #endif
24
25 LockedPoolManager* LockedPoolManager::_instance = nullptr;
26
27 /*******************************************************************************/
28 // Utilities
29 //
30 /** Align up to power of 2 */
31 static inline size_t align_up(size_t x, size_t align)
32 {
33 return (x + align - 1) & ~(align - 1);
34 }
35
36 /*******************************************************************************/
37 // Implementation: Arena
38
39 Arena::Arena(void *base_in, size_t size_in, size_t alignment_in):
40 base(base_in), end(static_cast<char*>(base_in) + size_in), alignment(alignment_in)
41 {
42 // Start with one free chunk that covers the entire arena
43 auto it = size_to_free_chunk.emplace(size_in, base);
44 chunks_free.emplace(base, it);
45 chunks_free_end.emplace(static_cast<char*>(base) + size_in, it);
46 }
47
48 Arena::~Arena() = default;
49
50 void* Arena::alloc(size_t size)
51 {
52 // Round to next multiple of alignment
53 size = align_up(size, alignment);
54
55 // Don't handle zero-sized chunks
56 if (size == 0)
57 return nullptr;
58
59 // Pick a large enough free-chunk. Returns an iterator pointing to the first element that is not less than key.
60 // This allocation strategy is best-fit. According to "Dynamic Storage Allocation: A Survey and Critical Review",
61 // Wilson et. al. 1995, https://www.scs.stanford.edu/14wi-cs140/sched/readings/wilson.pdf, best-fit and first-fit
62 // policies seem to work well in practice.
63 auto size_ptr_it = size_to_free_chunk.lower_bound(size);
64 if (size_ptr_it == size_to_free_chunk.end())
65 return nullptr;
66
67 // Create the used-chunk, taking its space from the end of the free-chunk
68 const size_t size_remaining = size_ptr_it->first - size;
69 char* const free_chunk = static_cast<char*>(size_ptr_it->second);
70 auto allocated = chunks_used.emplace(free_chunk + size_remaining, size).first;
71 chunks_free_end.erase(free_chunk + size_ptr_it->first);
72 if (size_ptr_it->first == size) {
73 // whole chunk is used up
74 chunks_free.erase(size_ptr_it->second);
75 } else {
76 // still some memory left in the chunk
77 auto it_remaining = size_to_free_chunk.emplace(size_remaining, size_ptr_it->second);
78 chunks_free[size_ptr_it->second] = it_remaining;
79 chunks_free_end.emplace(free_chunk + size_remaining, it_remaining);
80 }
81 size_to_free_chunk.erase(size_ptr_it);
82
83 return allocated->first;
84 }
85
86 void Arena::free(void *ptr)
87 {
88 // Freeing the nullptr pointer is OK.
89 if (ptr == nullptr) {
90 return;
91 }
92
93 // Remove chunk from used map
94 auto i = chunks_used.find(ptr);
95 if (i == chunks_used.end()) {
96 throw std::runtime_error("Arena: invalid or double free");
97 }
98 auto freed = std::make_pair(static_cast<char*>(i->first), i->second);
99 chunks_used.erase(i);
100
101 // coalesce freed with previous chunk
102 auto prev = chunks_free_end.find(freed.first);
103 if (prev != chunks_free_end.end()) {
104 freed.first -= prev->second->first;
105 freed.second += prev->second->first;
106 size_to_free_chunk.erase(prev->second);
107 chunks_free_end.erase(prev);
108 }
109
110 // coalesce freed with chunk after freed
111 auto next = chunks_free.find(freed.first + freed.second);
112 if (next != chunks_free.end()) {
113 freed.second += next->second->first;
114 size_to_free_chunk.erase(next->second);
115 chunks_free.erase(next);
116 }
117
118 // Add/set space with coalesced free chunk
119 auto it = size_to_free_chunk.emplace(freed.second, freed.first);
120 chunks_free[freed.first] = it;
121 chunks_free_end[freed.first + freed.second] = it;
122 }
123
124 Arena::Stats Arena::stats() const
125 {
126 Arena::Stats r{ 0, 0, 0, chunks_used.size(), chunks_free.size() };
127 for (const auto& chunk: chunks_used)
128 r.used += chunk.second;
129 for (const auto& chunk: chunks_free)
130 r.free += chunk.second->first;
131 r.total = r.used + r.free;
132 return r;
133 }
134
135 #ifdef ARENA_DEBUG
136 static void printchunk(void* base, size_t sz, bool used) {
137 std::cout <<
138 "0x" << std::hex << std::setw(16) << std::setfill('0') << base <<
139 " 0x" << std::hex << std::setw(16) << std::setfill('0') << sz <<
140 " 0x" << used << std::endl;
141 }
142 void Arena::walk() const
143 {
144 for (const auto& chunk: chunks_used)
145 printchunk(chunk.first, chunk.second, true);
146 std::cout << std::endl;
147 for (const auto& chunk: chunks_free)
148 printchunk(chunk.first, chunk.second->first, false);
149 std::cout << std::endl;
150 }
151 #endif
152
153 /*******************************************************************************/
154 // Implementation: Win32LockedPageAllocator
155
156 #ifdef WIN32
157 /** LockedPageAllocator specialized for Windows.
158 */
159 class Win32LockedPageAllocator: public LockedPageAllocator
160 {
161 public:
162 Win32LockedPageAllocator();
163 void* AllocateLocked(size_t len, bool *lockingSuccess) override;
164 void FreeLocked(void* addr, size_t len) override;
165 size_t GetLimit() override;
166 private:
167 size_t page_size;
168 };
169
170 Win32LockedPageAllocator::Win32LockedPageAllocator()
171 {
172 // Determine system page size in bytes
173 SYSTEM_INFO sSysInfo;
174 GetSystemInfo(&sSysInfo);
175 page_size = sSysInfo.dwPageSize;
176 }
177 void *Win32LockedPageAllocator::AllocateLocked(size_t len, bool *lockingSuccess)
178 {
179 len = align_up(len, page_size);
180 void *addr = VirtualAlloc(nullptr, len, MEM_COMMIT | MEM_RESERVE, PAGE_READWRITE);
181 if (addr) {
182 // VirtualLock is used to attempt to keep keying material out of swap. Note
183 // that it does not provide this as a guarantee, but, in practice, memory
184 // that has been VirtualLock'd almost never gets written to the pagefile
185 // except in rare circumstances where memory is extremely low.
186 *lockingSuccess = VirtualLock(const_cast<void*>(addr), len) != 0;
187 }
188 return addr;
189 }
190 void Win32LockedPageAllocator::FreeLocked(void* addr, size_t len)
191 {
192 len = align_up(len, page_size);
193 memory_cleanse(addr, len);
194 VirtualUnlock(const_cast<void*>(addr), len);
195 }
196
197 size_t Win32LockedPageAllocator::GetLimit()
198 {
199 size_t min, max;
200 if(GetProcessWorkingSetSize(GetCurrentProcess(), &min, &max) != 0) {
201 return min;
202 }
203 return std::numeric_limits<size_t>::max();
204 }
205 #endif
206
207 /*******************************************************************************/
208 // Implementation: PosixLockedPageAllocator
209
210 #ifndef WIN32
211 /** LockedPageAllocator specialized for OSes that don't try to be
212 * special snowflakes.
213 */
214 class PosixLockedPageAllocator: public LockedPageAllocator
215 {
216 public:
217 PosixLockedPageAllocator();
218 void* AllocateLocked(size_t len, bool *lockingSuccess) override;
219 void FreeLocked(void* addr, size_t len) override;
220 size_t GetLimit() override;
221 private:
222 size_t page_size;
223 };
224
225 PosixLockedPageAllocator::PosixLockedPageAllocator()
226 {
227 // Determine system page size in bytes
228 #if defined(PAGESIZE) // defined in limits.h
229 page_size = PAGESIZE;
230 #else // assume some POSIX OS
231 page_size = sysconf(_SC_PAGESIZE);
232 #endif
233 }
234
235 void *PosixLockedPageAllocator::AllocateLocked(size_t len, bool *lockingSuccess)
236 {
237 void *addr;
238 len = align_up(len, page_size);
239 addr = mmap(nullptr, len, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
240 if (addr == MAP_FAILED) {
241 return nullptr;
242 }
243 if (addr) {
244 *lockingSuccess = mlock(addr, len) == 0;
245 #if defined(MADV_DONTDUMP) // Linux
246 madvise(addr, len, MADV_DONTDUMP);
247 #elif defined(MADV_NOCORE) // FreeBSD
248 madvise(addr, len, MADV_NOCORE);
249 #endif
250 }
251 return addr;
252 }
253 void PosixLockedPageAllocator::FreeLocked(void* addr, size_t len)
254 {
255 len = align_up(len, page_size);
256 memory_cleanse(addr, len);
257 munlock(addr, len);
258 munmap(addr, len);
259 }
260 size_t PosixLockedPageAllocator::GetLimit()
261 {
262 #ifdef RLIMIT_MEMLOCK
263 struct rlimit rlim;
264 if (getrlimit(RLIMIT_MEMLOCK, &rlim) == 0) {
265 if (rlim.rlim_cur != RLIM_INFINITY &&
266 std::cmp_less_equal(rlim.rlim_cur, static_cast<rlim_t>(std::numeric_limits<size_t>::max()))) {
267 return rlim.rlim_cur;
268 }
269 }
270 #endif
271 return std::numeric_limits<size_t>::max();
272 }
273 #endif
274
275 /*******************************************************************************/
276 // Implementation: LockedPool
277
278 LockedPool::LockedPool(std::unique_ptr<LockedPageAllocator> allocator_in, LockingFailed_Callback lf_cb_in)
279 : allocator(std::move(allocator_in)), lf_cb(lf_cb_in)
280 {
281 }
282
283 LockedPool::~LockedPool() = default;
284
285 void* LockedPool::alloc(size_t size)
286 {
287 std::lock_guard<std::mutex> lock(mutex);
288
289 // Don't handle impossible sizes
290 if (size == 0 || size > ARENA_SIZE)
291 return nullptr;
292
293 // Try allocating from each current arena
294 for (auto &arena: arenas) {
295 void *addr = arena.alloc(size);
296 if (addr) {
297 return addr;
298 }
299 }
300 // If that fails, create a new one
301 if (new_arena(ARENA_SIZE, ARENA_ALIGN)) {
302 return arenas.back().alloc(size);
303 }
304 return nullptr;
305 }
306
307 void LockedPool::free(void *ptr)
308 {
309 std::lock_guard<std::mutex> lock(mutex);
310 // TODO we can do better than this linear search by keeping a map of arena
311 // extents to arena, and looking up the address.
312 for (auto &arena: arenas) {
313 if (arena.addressInArena(ptr)) {
314 arena.free(ptr);
315 return;
316 }
317 }
318 throw std::runtime_error("LockedPool: invalid address not pointing to any arena");
319 }
320
321 LockedPool::Stats LockedPool::stats() const
322 {
323 std::lock_guard<std::mutex> lock(mutex);
324 LockedPool::Stats r{0, 0, 0, cumulative_bytes_locked, 0, 0};
325 for (const auto &arena: arenas) {
326 Arena::Stats i = arena.stats();
327 r.used += i.used;
328 r.free += i.free;
329 r.total += i.total;
330 r.chunks_used += i.chunks_used;
331 r.chunks_free += i.chunks_free;
332 }
333 return r;
334 }
335
336 bool LockedPool::new_arena(size_t size, size_t align)
337 {
338 bool locked;
339 // If this is the first arena, handle this specially: Cap the upper size
340 // by the process limit. This makes sure that the first arena will at least
341 // be locked. An exception to this is if the process limit is 0:
342 // in this case no memory can be locked at all so we'll skip past this logic.
343 if (arenas.empty()) {
344 size_t limit = allocator->GetLimit();
345 if (limit > 0) {
346 size = std::min(size, limit);
347 }
348 }
349 void *addr = allocator->AllocateLocked(size, &locked);
350 if (!addr) {
351 return false;
352 }
353 if (locked) {
354 cumulative_bytes_locked += size;
355 } else if (lf_cb) { // Call the locking-failed callback if locking failed
356 if (!lf_cb()) { // If the callback returns false, free the memory and fail, otherwise consider the user warned and proceed.
357 allocator->FreeLocked(addr, size);
358 return false;
359 }
360 }
361 arenas.emplace_back(allocator.get(), addr, size, align);
362 return true;
363 }
364
365 LockedPool::LockedPageArena::LockedPageArena(LockedPageAllocator *allocator_in, void *base_in, size_t size_in, size_t align_in):
366 Arena(base_in, size_in, align_in), base(base_in), size(size_in), allocator(allocator_in)
367 {
368 }
369 LockedPool::LockedPageArena::~LockedPageArena()
370 {
371 allocator->FreeLocked(base, size);
372 }
373
374 /*******************************************************************************/
375 // Implementation: LockedPoolManager
376 //
377 LockedPoolManager::LockedPoolManager(std::unique_ptr<LockedPageAllocator> allocator_in):
378 LockedPool(std::move(allocator_in), &LockedPoolManager::LockingFailed)
379 {
380 }
381
382 bool LockedPoolManager::LockingFailed()
383 {
384 // TODO: log something but how? without including util.h
385 return true;
386 }
387
388 void LockedPoolManager::CreateInstance()
389 {
390 // Using a local static instance guarantees that the object is initialized
391 // when it's first needed and also deinitialized after all objects that use
392 // it are done with it. I can think of one unlikely scenario where we may
393 // have a static deinitialization order/problem, but the check in
394 // LockedPoolManagerBase's destructor helps us detect if that ever happens.
395 #ifdef WIN32
396 std::unique_ptr<LockedPageAllocator> allocator(new Win32LockedPageAllocator());
397 #else
398 std::unique_ptr<LockedPageAllocator> allocator(new PosixLockedPageAllocator());
399 #endif
400 static LockedPoolManager instance(std::move(allocator));
401 LockedPoolManager::_instance = &instance;
402 }
403
404 LockedPoolManager& LockedPoolManager::Instance()
405 {
406 static std::once_flag init_flag;
407 std::call_once(init_flag, LockedPoolManager::CreateInstance);
408 return *LockedPoolManager::_instance;
409 }
410