ceph/src/rocksdb/utilities/persistent_cache/block_cache_tier_file.h

   1 //  Copyright (c) 2013, 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 #pragma once
   6
   7 #ifndef ROCKSDB_LITE
   8
   9 #include <list>
  10 #include <memory>
  11 #include <string>
  12 #include <vector>
  13
  14 #include "rocksdb/comparator.h"
  15 #include "rocksdb/env.h"
  16
  17 #include "utilities/persistent_cache/block_cache_tier_file_buffer.h"
  18 #include "utilities/persistent_cache/lrulist.h"
  19 #include "utilities/persistent_cache/persistent_cache_tier.h"
  20 #include "utilities/persistent_cache/persistent_cache_util.h"
  21
  22 #include "port/port.h"
  23 #include "util/crc32c.h"
  24 #include "util/file_reader_writer.h"
  25 #include "util/mutexlock.h"
  26
  27 // The io code path of persistent cache uses pipelined architecture
  28 //
  29 // client -> In Queue <-- BlockCacheTier --> Out Queue <-- Writer <--> Kernel
  30 //
  31 // This would enable the system to scale for GB/s of throughput which is
  32 // expected with modern devies like NVM.
  33 //
  34 // The file level operations are encapsulated in the following abstractions
  35 //
  36 // BlockCacheFile
  37 //       ^
  38 //       |
  39 //       |
  40 // RandomAccessCacheFile (For reading)
  41 //       ^
  42 //       |
  43 //       |
  44 // WriteableCacheFile (For writing)
  45 //
  46 // Write IO code path :
  47 //
  48 namespace rocksdb {
  49
  50 class WriteableCacheFile;
  51 struct BlockInfo;
  52
  53 // Represents a logical record on device
  54 //
  55 // (L)ogical (B)lock (Address = { cache-file-id, offset, size }
  56 struct LogicalBlockAddress {
  57   LogicalBlockAddress() {}
  58   explicit LogicalBlockAddress(const uint32_t cache_id, const uint32_t off,
  59                                const uint16_t size)
  60       : cache_id_(cache_id), off_(off), size_(size) {}
  61
  62   uint32_t cache_id_ = 0;
  63   uint32_t off_ = 0;
  64   uint32_t size_ = 0;
  65 };
  66
  67 typedef LogicalBlockAddress LBA;
  68
  69 // class Writer
  70 //
  71 // Writer is the abstraction used for writing data to file. The component can be
  72 // multithreaded. It is the last step of write pipeline
  73 class Writer {
  74  public:
  75   explicit Writer(PersistentCacheTier* const cache) : cache_(cache) {}
  76   virtual ~Writer() {}
  77
  78   // write buffer to file at the given offset
  79   virtual void Write(WritableFile* const file, CacheWriteBuffer* buf,
  80                      const uint64_t file_off,
  81                      const std::function<void()> callback) = 0;
  82   // stop the writer
  83   virtual void Stop() = 0;
  84
  85   PersistentCacheTier* const cache_;
  86 };
  87
  88 // class BlockCacheFile
  89 //
  90 // Generic interface to support building file specialized for read/writing
  91 class BlockCacheFile : public LRUElement<BlockCacheFile> {
  92  public:
  93   explicit BlockCacheFile(const uint32_t cache_id)
  94       : LRUElement<BlockCacheFile>(), cache_id_(cache_id) {}
  95
  96   explicit BlockCacheFile(Env* const env, const std::string& dir,
  97                           const uint32_t cache_id)
  98       : LRUElement<BlockCacheFile>(),
  99         env_(env),
 100         dir_(dir),
 101         cache_id_(cache_id) {}
 102
 103   virtual ~BlockCacheFile() {}
 104
 105   // append key/value to file and return LBA locator to user
 106   virtual bool Append(const Slice& /*key*/, const Slice& /*val*/,
 107                       LBA* const /*lba*/) {
 108     assert(!"not implemented");
 109     return false;
 110   }
 111
 112   // read from the record locator (LBA) and return key, value and status
 113   virtual bool Read(const LBA& /*lba*/, Slice* /*key*/, Slice* /*block*/,
 114                     char* /*scratch*/) {
 115     assert(!"not implemented");
 116     return false;
 117   }
 118
 119   // get file path
 120   std::string Path() const {
 121     return dir_ + "/" + std::to_string(cache_id_) + ".rc";
 122   }
 123   // get cache ID
 124   uint32_t cacheid() const { return cache_id_; }
 125   // Add block information to file data
 126   // Block information is the list of index reference for this file
 127   virtual void Add(BlockInfo* binfo) {
 128     WriteLock _(&rwlock_);
 129     block_infos_.push_back(binfo);
 130   }
 131   // get block information
 132   std::list<BlockInfo*>& block_infos() { return block_infos_; }
 133   // delete file and return the size of the file
 134   virtual Status Delete(uint64_t* size);
 135
 136  protected:
 137   port::RWMutex rwlock_;               // synchronization mutex
 138   Env* const env_ = nullptr;           // Env for IO
 139   const std::string dir_;              // Directory name
 140   const uint32_t cache_id_;            // Cache id for the file
 141   std::list<BlockInfo*> block_infos_;  // List of index entries mapping to the
 142                                        // file content
 143 };
 144
 145 // class RandomAccessFile
 146 //
 147 // Thread safe implementation for reading random data from file
 148 class RandomAccessCacheFile : public BlockCacheFile {
 149  public:
 150   explicit RandomAccessCacheFile(Env* const env, const std::string& dir,
 151                                  const uint32_t cache_id,
 152                                  const shared_ptr<Logger>& log)
 153       : BlockCacheFile(env, dir, cache_id), log_(log) {}
 154
 155   virtual ~RandomAccessCacheFile() {}
 156
 157   // open file for reading
 158   bool Open(const bool enable_direct_reads);
 159   // read data from the disk
 160   bool Read(const LBA& lba, Slice* key, Slice* block, char* scratch) override;
 161
 162  private:
 163   std::unique_ptr<RandomAccessFileReader> freader_;
 164
 165  protected:
 166   bool OpenImpl(const bool enable_direct_reads);
 167   bool ParseRec(const LBA& lba, Slice* key, Slice* val, char* scratch);
 168
 169   std::shared_ptr<Logger> log_;  // log file
 170 };
 171
 172 // class WriteableCacheFile
 173 //
 174 // All writes to the files are cached in buffers. The buffers are flushed to
 175 // disk as they get filled up. When file size reaches a certain size, a new file
 176 // will be created provided there is free space
 177 class WriteableCacheFile : public RandomAccessCacheFile {
 178  public:
 179   explicit WriteableCacheFile(Env* const env, CacheWriteBufferAllocator* alloc,
 180                               Writer* writer, const std::string& dir,
 181                               const uint32_t cache_id, const uint32_t max_size,
 182                               const std::shared_ptr<Logger>& log)
 183       : RandomAccessCacheFile(env, dir, cache_id, log),
 184         alloc_(alloc),
 185         writer_(writer),
 186         max_size_(max_size) {}
 187
 188   virtual ~WriteableCacheFile();
 189
 190   // create file on disk
 191   bool Create(const bool enable_direct_writes, const bool enable_direct_reads);
 192
 193   // read data from logical file
 194   bool Read(const LBA& lba, Slice* key, Slice* block, char* scratch) override {
 195     ReadLock _(&rwlock_);
 196     const bool closed = eof_ && bufs_.empty();
 197     if (closed) {
 198       // the file is closed, read from disk
 199       return RandomAccessCacheFile::Read(lba, key, block, scratch);
 200     }
 201     // file is still being written, read from buffers
 202     return ReadBuffer(lba, key, block, scratch);
 203   }
 204
 205   // append data to end of file
 206   bool Append(const Slice&, const Slice&, LBA* const) override;
 207   // End-of-file
 208   bool Eof() const { return eof_; }
 209
 210  private:
 211   friend class ThreadedWriter;
 212
 213   static const size_t kFileAlignmentSize = 4 * 1024;  // align file size
 214
 215   bool ReadBuffer(const LBA& lba, Slice* key, Slice* block, char* scratch);
 216   bool ReadBuffer(const LBA& lba, char* data);
 217   bool ExpandBuffer(const size_t size);
 218   void DispatchBuffer();
 219   void BufferWriteDone();
 220   void CloseAndOpenForReading();
 221   void ClearBuffers();
 222   void Close();
 223
 224   // File layout in memory
 225   //
 226   // +------+------+------+------+------+------+
 227   // | b0   | b1   | b2   | b3   | b4   | b5   |
 228   // +------+------+------+------+------+------+
 229   //        ^                           ^
 230   //        |                           |
 231   //      buf_doff_                   buf_woff_
 232   //   (next buffer to           (next buffer to fill)
 233   //   flush to disk)
 234   //
 235   //  The buffers are flushed to disk serially for a given file
 236
 237   CacheWriteBufferAllocator* const alloc_ = nullptr;  // Buffer provider
 238   Writer* const writer_ = nullptr;                    // File writer thread
 239   std::unique_ptr<WritableFile> file_;   // RocksDB Env file abstraction
 240   std::vector<CacheWriteBuffer*> bufs_;  // Written buffers
 241   uint32_t size_ = 0;                    // Size of the file
 242   const uint32_t max_size_;              // Max size of the file
 243   bool eof_ = false;                     // End of file
 244   uint32_t disk_woff_ = 0;               // Offset to write on disk
 245   size_t buf_woff_ = 0;                  // off into bufs_ to write
 246   size_t buf_doff_ = 0;                  // off into bufs_ to dispatch
 247   size_t pending_ios_ = 0;               // Number of ios to disk in-progress
 248   bool enable_direct_reads_ = false;     // Should we enable direct reads
 249                                          // when reading from disk
 250 };
 251
 252 //
 253 // Abstraction to do writing to device. It is part of pipelined architecture.
 254 //
 255 class ThreadedWriter : public Writer {
 256  public:
 257   // Representation of IO to device
 258   struct IO {
 259     explicit IO(const bool signal) : signal_(signal) {}
 260     explicit IO(WritableFile* const file, CacheWriteBuffer* const buf,
 261                 const uint64_t file_off, const std::function<void()> callback)
 262         : file_(file), buf_(buf), file_off_(file_off), callback_(callback) {}
 263
 264     IO(const IO&) = default;
 265     IO& operator=(const IO&) = default;
 266     size_t Size() const { return sizeof(IO); }
 267
 268     WritableFile* file_ = nullptr;           // File to write to
 269     CacheWriteBuffer* const buf_ = nullptr;  // buffer to write
 270     uint64_t file_off_ = 0;                  // file offset
 271     bool signal_ = false;                    // signal to exit thread loop
 272     std::function<void()> callback_;         // Callback on completion
 273   };
 274
 275   explicit ThreadedWriter(PersistentCacheTier* const cache, const size_t qdepth,
 276                           const size_t io_size);
 277   virtual ~ThreadedWriter() { assert(threads_.empty()); }
 278
 279   void Stop() override;
 280   void Write(WritableFile* const file, CacheWriteBuffer* buf,
 281              const uint64_t file_off,
 282              const std::function<void()> callback) override;
 283
 284  private:
 285   void ThreadMain();
 286   void DispatchIO(const IO& io);
 287
 288   const size_t io_size_ = 0;
 289   BoundedQueue<IO> q_;
 290   std::vector<port::Thread> threads_;
 291 };
 292
 293 }  // namespace rocksdb
 294
 295 #endif