ceph/src/rocksdb/db/pinned_iterators_manager.h

   1 //  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
   2 //  This source code is licensed under both the GPLv2 (found in the
   3 //  COPYING file in the root directory) and Apache 2.0 License
   4 //  (found in the LICENSE.Apache file in the root directory).
   5 //
   6 #pragma once
   7 #include <algorithm>
   8 #include <memory>
   9 #include <utility>
  10 #include <vector>
  11
  12 #include "table/internal_iterator.h"
  13
  14 namespace ROCKSDB_NAMESPACE {
  15
  16 // PinnedIteratorsManager will be notified whenever we need to pin an Iterator
  17 // and it will be responsible for deleting pinned Iterators when they are
  18 // not needed anymore.
  19 class PinnedIteratorsManager : public Cleanable {
  20  public:
  21   PinnedIteratorsManager() : pinning_enabled(false) {}
  22   ~PinnedIteratorsManager() {
  23     if (pinning_enabled) {
  24       ReleasePinnedData();
  25     }
  26   }
  27
  28   // Move constructor and move assignment is allowed.
  29   PinnedIteratorsManager(PinnedIteratorsManager&& other) noexcept = default;
  30   PinnedIteratorsManager& operator=(PinnedIteratorsManager&& other) noexcept =
  31       default;
  32
  33   // Enable Iterators pinning
  34   void StartPinning() {
  35     assert(pinning_enabled == false);
  36     pinning_enabled = true;
  37   }
  38
  39   // Is pinning enabled ?
  40   bool PinningEnabled() { return pinning_enabled; }
  41
  42   // Take ownership of iter and delete it when ReleasePinnedData() is called
  43   void PinIterator(InternalIterator* iter, bool arena = false) {
  44     if (arena) {
  45       PinPtr(iter, &PinnedIteratorsManager::ReleaseArenaInternalIterator);
  46     } else {
  47       PinPtr(iter, &PinnedIteratorsManager::ReleaseInternalIterator);
  48     }
  49   }
  50
  51   using ReleaseFunction = void (*)(void* arg1);
  52   void PinPtr(void* ptr, ReleaseFunction release_func) {
  53     assert(pinning_enabled);
  54     if (ptr == nullptr) {
  55       return;
  56     }
  57     pinned_ptrs_.emplace_back(ptr, release_func);
  58   }
  59
  60   // Release pinned Iterators
  61   inline void ReleasePinnedData() {
  62     assert(pinning_enabled == true);
  63     pinning_enabled = false;
  64
  65     // Remove duplicate pointers
  66     std::sort(pinned_ptrs_.begin(), pinned_ptrs_.end());
  67     auto unique_end = std::unique(pinned_ptrs_.begin(), pinned_ptrs_.end());
  68
  69     for (auto i = pinned_ptrs_.begin(); i != unique_end; ++i) {
  70       void* ptr = i->first;
  71       ReleaseFunction release_func = i->second;
  72       release_func(ptr);
  73     }
  74     pinned_ptrs_.clear();
  75     // Also do cleanups from the base Cleanable
  76     Cleanable::Reset();
  77   }
  78
  79  private:
  80   static void ReleaseInternalIterator(void* ptr) {
  81     delete reinterpret_cast<InternalIterator*>(ptr);
  82   }
  83
  84   static void ReleaseArenaInternalIterator(void* ptr) {
  85     reinterpret_cast<InternalIterator*>(ptr)->~InternalIterator();
  86   }
  87
  88   bool pinning_enabled;
  89   std::vector<std::pair<void*, ReleaseFunction>> pinned_ptrs_;
  90 };
  91
  92 }  // namespace ROCKSDB_NAMESPACE