net/disk_cache/blockfile/stats.h

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef NET_DISK_CACHE_BLOCKFILE_STATS_H_
   6 #define NET_DISK_CACHE_BLOCKFILE_STATS_H_
   7
   8 #include <string>
   9 #include <vector>
  10
  11 #include "base/basictypes.h"
  12 #include "net/disk_cache/blockfile/addr.h"
  13
  14 namespace base {
  15 class HistogramSamples;
  16 }  // namespace base
  17
  18 namespace disk_cache {
  19
  20 typedef std::vector<std::pair<std::string, std::string> > StatsItems;
  21
  22 // This class stores cache-specific usage information, for tunning purposes.
  23 class Stats {
  24  public:
  25   static const int kDataSizesLength = 28;
  26   enum Counters {
  27     MIN_COUNTER = 0,
  28     OPEN_MISS = MIN_COUNTER,
  29     OPEN_HIT,
  30     CREATE_MISS,
  31     CREATE_HIT,
  32     RESURRECT_HIT,
  33     CREATE_ERROR,
  34     TRIM_ENTRY,
  35     DOOM_ENTRY,
  36     DOOM_CACHE,
  37     INVALID_ENTRY,
  38     OPEN_ENTRIES,  // Average number of open entries.
  39     MAX_ENTRIES,  // Maximum number of open entries.
  40     TIMER,
  41     READ_DATA,
  42     WRITE_DATA,
  43     OPEN_RANKINGS,  // An entry has to be read just to modify rankings.
  44     GET_RANKINGS,  // We got the ranking info without reading the whole entry.
  45     FATAL_ERROR,
  46     LAST_REPORT,  // Time of the last time we sent a report.
  47     LAST_REPORT_TIMER,  // Timer count of the last time we sent a report.
  48     DOOM_RECENT,  // The cache was partially cleared.
  49     UNUSED,  // Was: ga.js was evicted from the cache.
  50     MAX_COUNTER
  51   };
  52
  53   Stats();
  54   ~Stats();
  55
  56   // Initializes this object with |data| from disk.
  57   bool Init(void* data, int num_bytes, Addr address);
  58
  59   // Generates a size distribution histogram.
  60   void InitSizeHistogram();
  61
  62   // Returns the number of bytes needed to store the stats on disk.
  63   int StorageSize();
  64
  65   // Tracks changes to the stoage space used by an entry.
  66   void ModifyStorageStats(int32 old_size, int32 new_size);
  67
  68   // Tracks general events.
  69   void OnEvent(Counters an_event);
  70   void SetCounter(Counters counter, int64 value);
  71   int64 GetCounter(Counters counter) const;
  72
  73   void GetItems(StatsItems* items);
  74   int GetHitRatio() const;
  75   int GetResurrectRatio() const;
  76   void ResetRatios();
  77
  78   // Returns the lower bound of the space used by entries bigger than 512 KB.
  79   int GetLargeEntriesSize();
  80
  81   // Writes the stats into |data|, to be stored at the given cache address.
  82   // Returns the number of bytes copied.
  83   int SerializeStats(void* data, int num_bytes, Addr* address);
  84
  85  private:
  86   // Supports generation of SizeStats histogram data.
  87   int GetBucketRange(size_t i) const;
  88   int GetStatsBucket(int32 size);
  89   int GetRatio(Counters hit, Counters miss) const;
  90
  91   Addr storage_addr_;
  92   int data_sizes_[kDataSizesLength];
  93   int64 counters_[MAX_COUNTER];
  94
  95   DISALLOW_COPY_AND_ASSIGN(Stats);
  96 };
  97
  98 }  // namespace disk_cache
  99
 100 #endif  // NET_DISK_CACHE_BLOCKFILE_STATS_H_