src/support/lockedpool.cpp

   1 // Copyright (c) 2016-2017 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 #if defined(HAVE_CONFIG_H)
   9 #include <config/bitcoin-config.h>
  10 #endif
  11
  12 #ifdef WIN32
  13 #ifdef _WIN32_WINNT
  14 #undef _WIN32_WINNT
  15 #endif
  16 #define _WIN32_WINNT 0x0501
  17 #define WIN32_LEAN_AND_MEAN 1
  18 #ifndef NOMINMAX
  19 #define NOMINMAX
  20 #endif
  21 #include <windows.h>
  22 #else
  23 #include <sys/mman.h> // for mmap
  24 #include <sys/resource.h> // for getrlimit
  25 #include <limits.h> // for PAGESIZE
  26 #include <unistd.h> // for sysconf
  27 #endif
  28
  29 #include <algorithm>
  30
  31 LockedPoolManager* LockedPoolManager::_instance = nullptr;
  32 std::once_flag LockedPoolManager::init_flag;
  33
  34 /*******************************************************************************/
  35 // Utilities
  36 //
  37 /** Align up to power of 2 */
  38 static inline size_t align_up(size_t x, size_t align)
  39 {
  40     return (x + align - 1) & ~(align - 1);
  41 }
  42
  43 /*******************************************************************************/
  44 // Implementation: Arena
  45
  46 Arena::Arena(void *base_in, size_t size_in, size_t alignment_in):
  47     base(static_cast<char*>(base_in)), end(static_cast<char*>(base_in) + size_in), alignment(alignment_in)
  48 {
  49     // Start with one free chunk that covers the entire arena
  50     chunks_free.emplace(base, size_in);
  51 }
  52
  53 Arena::~Arena()
  54 {
  55 }
  56
  57 void* Arena::alloc(size_t size)
  58 {
  59     // Round to next multiple of alignment
  60     size = align_up(size, alignment);
  61
  62     // Don't handle zero-sized chunks
  63     if (size == 0)
  64         return nullptr;
  65
  66     // Pick a large enough free-chunk
  67     auto it = std::find_if(chunks_free.begin(), chunks_free.end(),
  68         [=](const std::map<char*, size_t>::value_type& chunk){ return chunk.second >= size; });
  69     if (it == chunks_free.end())
  70         return nullptr;
  71
  72     // Create the used-chunk, taking its space from the end of the free-chunk
  73     auto alloced = chunks_used.emplace(it->first + it->second - size, size).first;
  74     if (!(it->second -= size))
  75         chunks_free.erase(it);
  76     return reinterpret_cast<void*>(alloced->first);
  77 }
  78
  79 /* extend the Iterator if other begins at its end */
  80 template <class Iterator, class Pair> bool extend(Iterator it, const Pair& other) {
  81     if (it->first + it->second == other.first) {
  82         it->second += other.second;
  83         return true;
  84     }
  85     return false;
  86 }
  87
  88 void Arena::free(void *ptr)
  89 {
  90     // Freeing the nullptr pointer is OK.
  91     if (ptr == nullptr) {
  92         return;
  93     }
  94
  95     // Remove chunk from used map
  96     auto i = chunks_used.find(static_cast<char*>(ptr));
  97     if (i == chunks_used.end()) {
  98         throw std::runtime_error("Arena: invalid or double free");
  99     }
 100     auto freed = *i;
 101     chunks_used.erase(i);
 102
 103     // Add space to free map, coalescing contiguous chunks
 104     auto next = chunks_free.upper_bound(freed.first);
 105     auto prev = (next == chunks_free.begin()) ? chunks_free.end() : std::prev(next);
 106     if (prev == chunks_free.end() || !extend(prev, freed))
 107         prev = chunks_free.emplace_hint(next, freed);
 108     if (next != chunks_free.end() && extend(prev, *next))
 109         chunks_free.erase(next);
 110 }
 111
 112 Arena::Stats Arena::stats() const
 113 {
 114     Arena::Stats r{ 0, 0, 0, chunks_used.size(), chunks_free.size() };
 115     for (const auto& chunk: chunks_used)
 116         r.used += chunk.second;
 117     for (const auto& chunk: chunks_free)
 118         r.free += chunk.second;
 119     r.total = r.used + r.free;
 120     return r;
 121 }
 122
 123 #ifdef ARENA_DEBUG
 124 void printchunk(char* base, size_t sz, bool used) {
 125     std::cout <<
 126         "0x" << std::hex << std::setw(16) << std::setfill('0') << base <<
 127         " 0x" << std::hex << std::setw(16) << std::setfill('0') << sz <<
 128         " 0x" << used << std::endl;
 129 }
 130 void Arena::walk() const
 131 {
 132     for (const auto& chunk: chunks_used)
 133         printchunk(chunk.first, chunk.second, true);
 134     std::cout << std::endl;
 135     for (const auto& chunk: chunks_free)
 136         printchunk(chunk.first, chunk.second, false);
 137     std::cout << std::endl;
 138 }
 139 #endif
 140
 141 /*******************************************************************************/
 142 // Implementation: Win32LockedPageAllocator
 143
 144 #ifdef WIN32
 145 /** LockedPageAllocator specialized for Windows.
 146  */
 147 class Win32LockedPageAllocator: public LockedPageAllocator
 148 {
 149 public:
 150     Win32LockedPageAllocator();
 151     void* AllocateLocked(size_t len, bool *lockingSuccess) override;
 152     void FreeLocked(void* addr, size_t len) override;
 153     size_t GetLimit() override;
 154 private:
 155     size_t page_size;
 156 };
 157
 158 Win32LockedPageAllocator::Win32LockedPageAllocator()
 159 {
 160     // Determine system page size in bytes
 161     SYSTEM_INFO sSysInfo;
 162     GetSystemInfo(&sSysInfo);
 163     page_size = sSysInfo.dwPageSize;
 164 }
 165 void *Win32LockedPageAllocator::AllocateLocked(size_t len, bool *lockingSuccess)
 166 {
 167     len = align_up(len, page_size);
 168     void *addr = VirtualAlloc(nullptr, len, MEM_COMMIT | MEM_RESERVE, PAGE_READWRITE);
 169     if (addr) {
 170         // VirtualLock is used to attempt to keep keying material out of swap. Note
 171         // that it does not provide this as a guarantee, but, in practice, memory
 172         // that has been VirtualLock'd almost never gets written to the pagefile
 173         // except in rare circumstances where memory is extremely low.
 174         *lockingSuccess = VirtualLock(const_cast<void*>(addr), len) != 0;
 175     }
 176     return addr;
 177 }
 178 void Win32LockedPageAllocator::FreeLocked(void* addr, size_t len)
 179 {
 180     len = align_up(len, page_size);
 181     memory_cleanse(addr, len);
 182     VirtualUnlock(const_cast<void*>(addr), len);
 183 }
 184
 185 size_t Win32LockedPageAllocator::GetLimit()
 186 {
 187     // TODO is there a limit on windows, how to get it?
 188     return std::numeric_limits<size_t>::max();
 189 }
 190 #endif
 191
 192 /*******************************************************************************/
 193 // Implementation: PosixLockedPageAllocator
 194
 195 #ifndef WIN32
 196 /** LockedPageAllocator specialized for OSes that don't try to be
 197  * special snowflakes.
 198  */
 199 class PosixLockedPageAllocator: public LockedPageAllocator
 200 {
 201 public:
 202     PosixLockedPageAllocator();
 203     void* AllocateLocked(size_t len, bool *lockingSuccess) override;
 204     void FreeLocked(void* addr, size_t len) override;
 205     size_t GetLimit() override;
 206 private:
 207     size_t page_size;
 208 };
 209
 210 PosixLockedPageAllocator::PosixLockedPageAllocator()
 211 {
 212     // Determine system page size in bytes
 213 #if defined(PAGESIZE) // defined in limits.h
 214     page_size = PAGESIZE;
 215 #else                   // assume some POSIX OS
 216     page_size = sysconf(_SC_PAGESIZE);
 217 #endif
 218 }
 219
 220 // Some systems (at least OS X) do not define MAP_ANONYMOUS yet and define
 221 // MAP_ANON which is deprecated
 222 #ifndef MAP_ANONYMOUS
 223 #define MAP_ANONYMOUS MAP_ANON
 224 #endif
 225
 226 void *PosixLockedPageAllocator::AllocateLocked(size_t len, bool *lockingSuccess)
 227 {
 228     void *addr;
 229     len = align_up(len, page_size);
 230     addr = mmap(nullptr, len, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
 231     if (addr) {
 232         *lockingSuccess = mlock(addr, len) == 0;
 233     }
 234     return addr;
 235 }
 236 void PosixLockedPageAllocator::FreeLocked(void* addr, size_t len)
 237 {
 238     len = align_up(len, page_size);
 239     memory_cleanse(addr, len);
 240     munlock(addr, len);
 241     munmap(addr, len);
 242 }
 243 size_t PosixLockedPageAllocator::GetLimit()
 244 {
 245 #ifdef RLIMIT_MEMLOCK
 246     struct rlimit rlim;
 247     if (getrlimit(RLIMIT_MEMLOCK, &rlim) == 0) {
 248         if (rlim.rlim_cur != RLIM_INFINITY) {
 249             return rlim.rlim_cur;
 250         }
 251     }
 252 #endif
 253     return std::numeric_limits<size_t>::max();
 254 }
 255 #endif
 256
 257 /*******************************************************************************/
 258 // Implementation: LockedPool
 259
 260 LockedPool::LockedPool(std::unique_ptr<LockedPageAllocator> allocator_in, LockingFailed_Callback lf_cb_in):
 261     allocator(std::move(allocator_in)), lf_cb(lf_cb_in), cumulative_bytes_locked(0)
 262 {
 263 }
 264
 265 LockedPool::~LockedPool()
 266 {
 267 }
 268 void* LockedPool::alloc(size_t size)
 269 {
 270     std::lock_guard<std::mutex> lock(mutex);
 271
 272     // Don't handle impossible sizes
 273     if (size == 0 || size > ARENA_SIZE)
 274         return nullptr;
 275
 276     // Try allocating from each current arena
 277     for (auto &arena: arenas) {
 278         void *addr = arena.alloc(size);
 279         if (addr) {
 280             return addr;
 281         }
 282     }
 283     // If that fails, create a new one
 284     if (new_arena(ARENA_SIZE, ARENA_ALIGN)) {
 285         return arenas.back().alloc(size);
 286     }
 287     return nullptr;
 288 }
 289
 290 void LockedPool::free(void *ptr)
 291 {
 292     std::lock_guard<std::mutex> lock(mutex);
 293     // TODO we can do better than this linear search by keeping a map of arena
 294     // extents to arena, and looking up the address.
 295     for (auto &arena: arenas) {
 296         if (arena.addressInArena(ptr)) {
 297             arena.free(ptr);
 298             return;
 299         }
 300     }
 301     throw std::runtime_error("LockedPool: invalid address not pointing to any arena");
 302 }
 303
 304 LockedPool::Stats LockedPool::stats() const
 305 {
 306     std::lock_guard<std::mutex> lock(mutex);
 307     LockedPool::Stats r{0, 0, 0, cumulative_bytes_locked, 0, 0};
 308     for (const auto &arena: arenas) {
 309         Arena::Stats i = arena.stats();
 310         r.used += i.used;
 311         r.free += i.free;
 312         r.total += i.total;
 313         r.chunks_used += i.chunks_used;
 314         r.chunks_free += i.chunks_free;
 315     }
 316     return r;
 317 }
 318
 319 bool LockedPool::new_arena(size_t size, size_t align)
 320 {
 321     bool locked;
 322     // If this is the first arena, handle this specially: Cap the upper size
 323     // by the process limit. This makes sure that the first arena will at least
 324     // be locked. An exception to this is if the process limit is 0:
 325     // in this case no memory can be locked at all so we'll skip past this logic.
 326     if (arenas.empty()) {
 327         size_t limit = allocator->GetLimit();
 328         if (limit > 0) {
 329             size = std::min(size, limit);
 330         }
 331     }
 332     void *addr = allocator->AllocateLocked(size, &locked);
 333     if (!addr) {
 334         return false;
 335     }
 336     if (locked) {
 337         cumulative_bytes_locked += size;
 338     } else if (lf_cb) { // Call the locking-failed callback if locking failed
 339         if (!lf_cb()) { // If the callback returns false, free the memory and fail, otherwise consider the user warned and proceed.
 340             allocator->FreeLocked(addr, size);
 341             return false;
 342         }
 343     }
 344     arenas.emplace_back(allocator.get(), addr, size, align);
 345     return true;
 346 }
 347
 348 LockedPool::LockedPageArena::LockedPageArena(LockedPageAllocator *allocator_in, void *base_in, size_t size_in, size_t align_in):
 349     Arena(base_in, size_in, align_in), base(base_in), size(size_in), allocator(allocator_in)
 350 {
 351 }
 352 LockedPool::LockedPageArena::~LockedPageArena()
 353 {
 354     allocator->FreeLocked(base, size);
 355 }
 356
 357 /*******************************************************************************/
 358 // Implementation: LockedPoolManager
 359 //
 360 LockedPoolManager::LockedPoolManager(std::unique_ptr<LockedPageAllocator> allocator_in):
 361     LockedPool(std::move(allocator_in), &LockedPoolManager::LockingFailed)
 362 {
 363 }
 364
 365 bool LockedPoolManager::LockingFailed()
 366 {
 367     // TODO: log something but how? without including util.h
 368     return true;
 369 }
 370
 371 void LockedPoolManager::CreateInstance()
 372 {
 373     // Using a local static instance guarantees that the object is initialized
 374     // when it's first needed and also deinitialized after all objects that use
 375     // it are done with it.  I can think of one unlikely scenario where we may
 376     // have a static deinitialization order/problem, but the check in
 377     // LockedPoolManagerBase's destructor helps us detect if that ever happens.
 378 #ifdef WIN32
 379     std::unique_ptr<LockedPageAllocator> allocator(new Win32LockedPageAllocator());
 380 #else
 381     std::unique_ptr<LockedPageAllocator> allocator(new PosixLockedPageAllocator());
 382 #endif
 383     static LockedPoolManager instance(std::move(allocator));
 384     LockedPoolManager::_instance = &instance;
 385 }