libsanitizer/sanitizer_common/sanitizer_quarantine.h

   1 //===-- sanitizer_quarantine.h ----------------------------------*- C++ -*-===//
   2 //
   3 // This file is distributed under the University of Illinois Open Source
   4 // License. See LICENSE.TXT for details.
   5 //
   6 //===----------------------------------------------------------------------===//
   7 //
   8 // Memory quarantine for AddressSanitizer and potentially other tools.
   9 // Quarantine caches some specified amount of memory in per-thread caches,
  10 // then evicts to global FIFO queue. When the queue reaches specified threshold,
  11 // oldest memory is recycled.
  12 //
  13 //===----------------------------------------------------------------------===//
  14
  15 #ifndef SANITIZER_QUARANTINE_H
  16 #define SANITIZER_QUARANTINE_H
  17
  18 #include "sanitizer_internal_defs.h"
  19 #include "sanitizer_mutex.h"
  20 #include "sanitizer_list.h"
  21
  22 namespace __sanitizer {
  23
  24 template<typename Node> class QuarantineCache;
  25
  26 struct QuarantineBatch {
  27   static const uptr kSize = 1021;
  28   QuarantineBatch *next;
  29   uptr size;
  30   uptr count;
  31   void *batch[kSize];
  32
  33   void init(void *ptr, uptr size) {
  34     count = 1;
  35     batch[0] = ptr;
  36     this->size = size + sizeof(QuarantineBatch);  // Account for the batch size.
  37   }
  38
  39   // The total size of quarantined nodes recorded in this batch.
  40   uptr quarantined_size() const {
  41     return size - sizeof(QuarantineBatch);
  42   }
  43
  44   void push_back(void *ptr, uptr size) {
  45     CHECK_LT(count, kSize);
  46     batch[count++] = ptr;
  47     this->size += size;
  48   }
  49
  50   bool can_merge(const QuarantineBatch* const from) const {
  51     return count + from->count <= kSize;
  52   }
  53
  54   void merge(QuarantineBatch* const from) {
  55     CHECK_LE(count + from->count, kSize);
  56     CHECK_GE(size, sizeof(QuarantineBatch));
  57
  58     for (uptr i = 0; i < from->count; ++i)
  59       batch[count + i] = from->batch[i];
  60     count += from->count;
  61     size += from->quarantined_size();
  62
  63     from->count = 0;
  64     from->size = sizeof(QuarantineBatch);
  65   }
  66 };
  67
  68 COMPILER_CHECK(sizeof(QuarantineBatch) <= (1 << 13));  // 8Kb.
  69
  70 // The callback interface is:
  71 // void Callback::Recycle(Node *ptr);
  72 // void *cb.Allocate(uptr size);
  73 // void cb.Deallocate(void *ptr);
  74 template<typename Callback, typename Node>
  75 class Quarantine {
  76  public:
  77   typedef QuarantineCache<Callback> Cache;
  78
  79   explicit Quarantine(LinkerInitialized)
  80       : cache_(LINKER_INITIALIZED) {
  81   }
  82
  83   void Init(uptr size, uptr cache_size) {
  84     // Thread local quarantine size can be zero only when global quarantine size
  85     // is zero (it allows us to perform just one atomic read per Put() call).
  86     CHECK((size == 0 && cache_size == 0) || cache_size != 0);
  87
  88     atomic_store(&max_size_, size, memory_order_relaxed);
  89     atomic_store(&min_size_, size / 10 * 9,
  90                  memory_order_relaxed);  // 90% of max size.
  91     atomic_store(&max_cache_size_, cache_size, memory_order_relaxed);
  92   }
  93
  94   uptr GetSize() const { return atomic_load(&max_size_, memory_order_relaxed); }
  95   uptr GetCacheSize() const {
  96     return atomic_load(&max_cache_size_, memory_order_relaxed);
  97   }
  98
  99   void Put(Cache *c, Callback cb, Node *ptr, uptr size) {
 100     uptr cache_size = GetCacheSize();
 101     if (cache_size) {
 102       c->Enqueue(cb, ptr, size);
 103     } else {
 104       // GetCacheSize() == 0 only when GetSize() == 0 (see Init).
 105       cb.Recycle(ptr);
 106     }
 107     // Check cache size anyway to accommodate for runtime cache_size change.
 108     if (c->Size() > cache_size)
 109       Drain(c, cb);
 110   }
 111
 112   void NOINLINE Drain(Cache *c, Callback cb) {
 113     {
 114       SpinMutexLock l(&cache_mutex_);
 115       cache_.Transfer(c);
 116     }
 117     if (cache_.Size() > GetSize() && recycle_mutex_.TryLock())
 118       Recycle(cb);
 119   }
 120
 121   void PrintStats() const {
 122     // It assumes that the world is stopped, just as the allocator's PrintStats.
 123     Printf("Quarantine limits: global: %zdMb; thread local: %zdKb\n",
 124            GetSize() >> 20, GetCacheSize() >> 10);
 125     cache_.PrintStats();
 126   }
 127
 128  private:
 129   // Read-only data.
 130   char pad0_[kCacheLineSize];
 131   atomic_uintptr_t max_size_;
 132   atomic_uintptr_t min_size_;
 133   atomic_uintptr_t max_cache_size_;
 134   char pad1_[kCacheLineSize];
 135   SpinMutex cache_mutex_;
 136   SpinMutex recycle_mutex_;
 137   Cache cache_;
 138   char pad2_[kCacheLineSize];
 139
 140   void NOINLINE Recycle(Callback cb) {
 141     Cache tmp;
 142     uptr min_size = atomic_load(&min_size_, memory_order_relaxed);
 143     {
 144       SpinMutexLock l(&cache_mutex_);
 145       // Go over the batches and merge partially filled ones to
 146       // save some memory, otherwise batches themselves (since the memory used
 147       // by them is counted against quarantine limit) can overcome the actual
 148       // user's quarantined chunks, which diminishes the purpose of the
 149       // quarantine.
 150       uptr cache_size = cache_.Size();
 151       uptr overhead_size = cache_.OverheadSize();
 152       CHECK_GE(cache_size, overhead_size);
 153       // Do the merge only when overhead exceeds this predefined limit (might
 154       // require some tuning). It saves us merge attempt when the batch list
 155       // quarantine is unlikely to contain batches suitable for merge.
 156       const uptr kOverheadThresholdPercents = 100;
 157       if (cache_size > overhead_size &&
 158           overhead_size * (100 + kOverheadThresholdPercents) >
 159               cache_size * kOverheadThresholdPercents) {
 160         cache_.MergeBatches(&tmp);
 161       }
 162       // Extract enough chunks from the quarantine to get below the max
 163       // quarantine size and leave some leeway for the newly quarantined chunks.
 164       while (cache_.Size() > min_size) {
 165         tmp.EnqueueBatch(cache_.DequeueBatch());
 166       }
 167     }
 168     recycle_mutex_.Unlock();
 169     DoRecycle(&tmp, cb);
 170   }
 171
 172   void NOINLINE DoRecycle(Cache *c, Callback cb) {
 173     while (QuarantineBatch *b = c->DequeueBatch()) {
 174       const uptr kPrefetch = 16;
 175       CHECK(kPrefetch <= ARRAY_SIZE(b->batch));
 176       for (uptr i = 0; i < kPrefetch; i++)
 177         PREFETCH(b->batch[i]);
 178       for (uptr i = 0, count = b->count; i < count; i++) {
 179         if (i + kPrefetch < count)
 180           PREFETCH(b->batch[i + kPrefetch]);
 181         cb.Recycle((Node*)b->batch[i]);
 182       }
 183       cb.Deallocate(b);
 184     }
 185   }
 186 };
 187
 188 // Per-thread cache of memory blocks.
 189 template<typename Callback>
 190 class QuarantineCache {
 191  public:
 192   explicit QuarantineCache(LinkerInitialized) {
 193   }
 194
 195   QuarantineCache()
 196       : size_() {
 197     list_.clear();
 198   }
 199
 200   // Total memory used, including internal accounting.
 201   uptr Size() const {
 202     return atomic_load(&size_, memory_order_relaxed);
 203   }
 204
 205   // Memory used for internal accounting.
 206   uptr OverheadSize() const {
 207     return list_.size() * sizeof(QuarantineBatch);
 208   }
 209
 210   void Enqueue(Callback cb, void *ptr, uptr size) {
 211     if (list_.empty() || list_.back()->count == QuarantineBatch::kSize) {
 212       QuarantineBatch *b = (QuarantineBatch *)cb.Allocate(sizeof(*b));
 213       CHECK(b);
 214       b->init(ptr, size);
 215       EnqueueBatch(b);
 216     } else {
 217       list_.back()->push_back(ptr, size);
 218       SizeAdd(size);
 219     }
 220   }
 221
 222   void Transfer(QuarantineCache *from_cache) {
 223     list_.append_back(&from_cache->list_);
 224     SizeAdd(from_cache->Size());
 225
 226     atomic_store(&from_cache->size_, 0, memory_order_relaxed);
 227   }
 228
 229   void EnqueueBatch(QuarantineBatch *b) {
 230     list_.push_back(b);
 231     SizeAdd(b->size);
 232   }
 233
 234   QuarantineBatch *DequeueBatch() {
 235     if (list_.empty())
 236       return nullptr;
 237     QuarantineBatch *b = list_.front();
 238     list_.pop_front();
 239     SizeSub(b->size);
 240     return b;
 241   }
 242
 243   void MergeBatches(QuarantineCache *to_deallocate) {
 244     uptr extracted_size = 0;
 245     QuarantineBatch *current = list_.front();
 246     while (current && current->next) {
 247       if (current->can_merge(current->next)) {
 248         QuarantineBatch *extracted = current->next;
 249         // Move all the chunks into the current batch.
 250         current->merge(extracted);
 251         CHECK_EQ(extracted->count, 0);
 252         CHECK_EQ(extracted->size, sizeof(QuarantineBatch));
 253         // Remove the next batch from the list and account for its size.
 254         list_.extract(current, extracted);
 255         extracted_size += extracted->size;
 256         // Add it to deallocation list.
 257         to_deallocate->EnqueueBatch(extracted);
 258       } else {
 259         current = current->next;
 260       }
 261     }
 262     SizeSub(extracted_size);
 263   }
 264
 265   void PrintStats() const {
 266     uptr batch_count = 0;
 267     uptr total_overhead_bytes = 0;
 268     uptr total_bytes = 0;
 269     uptr total_quarantine_chunks = 0;
 270     for (List::ConstIterator it = list_.begin(); it != list_.end(); ++it) {
 271       batch_count++;
 272       total_bytes += (*it).size;
 273       total_overhead_bytes += (*it).size - (*it).quarantined_size();
 274       total_quarantine_chunks += (*it).count;
 275     }
 276     uptr quarantine_chunks_capacity = batch_count * QuarantineBatch::kSize;
 277     int chunks_usage_percent = quarantine_chunks_capacity == 0 ?
 278         0 : total_quarantine_chunks * 100 / quarantine_chunks_capacity;
 279     uptr total_quarantined_bytes = total_bytes - total_overhead_bytes;
 280     int memory_overhead_percent = total_quarantined_bytes == 0 ?
 281         0 : total_overhead_bytes * 100 / total_quarantined_bytes;
 282     Printf("Global quarantine stats: batches: %zd; bytes: %zd (user: %zd); "
 283            "chunks: %zd (capacity: %zd); %d%% chunks used; %d%% memory overhead"
 284            "\n",
 285            batch_count, total_bytes, total_quarantined_bytes,
 286            total_quarantine_chunks, quarantine_chunks_capacity,
 287            chunks_usage_percent, memory_overhead_percent);
 288   }
 289
 290  private:
 291   typedef IntrusiveList<QuarantineBatch> List;
 292
 293   List list_;
 294   atomic_uintptr_t size_;
 295
 296   void SizeAdd(uptr add) {
 297     atomic_store(&size_, Size() + add, memory_order_relaxed);
 298   }
 299   void SizeSub(uptr sub) {
 300     atomic_store(&size_, Size() - sub, memory_order_relaxed);
 301   }
 302 };
 303
 304 } // namespace __sanitizer
 305
 306 #endif // SANITIZER_QUARANTINE_H