net/disk_cache/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_STATS_H_
   6 #define NET_DISK_CACHE_STATS_H_
   7
   8 #include <string>
   9 #include <vector>
  10
  11 #include "base/basictypes.h"
  12 #include "net/disk_cache/addr.h"
  13 #include "net/disk_cache/stats_histogram.h"
  14
  15 namespace base {
  16 class HistogramSamples;
  17 }  // namespace base
  18
  19 namespace disk_cache {
  20
  21 typedef std::vector<std::pair<std::string, std::string> > StatsItems;
  22
  23 // This class stores cache-specific usage information, for tunning purposes.
  24 class Stats {
  25  public:
  26   static const int kDataSizesLength = 28;
  27   enum Counters {
  28     MIN_COUNTER = 0,
  29     OPEN_MISS = MIN_COUNTER,
  30     OPEN_HIT,
  31     CREATE_MISS,
  32     CREATE_HIT,
  33     RESURRECT_HIT,
  34     CREATE_ERROR,
  35     TRIM_ENTRY,
  36     DOOM_ENTRY,
  37     DOOM_CACHE,
  38     INVALID_ENTRY,
  39     OPEN_ENTRIES,  // Average number of open entries.
  40     MAX_ENTRIES,  // Maximum number of open entries.
  41     TIMER,
  42     READ_DATA,
  43     WRITE_DATA,
  44     OPEN_RANKINGS,  // An entry has to be read just to modify rankings.
  45     GET_RANKINGS,  // We got the ranking info without reading the whole entry.
  46     FATAL_ERROR,
  47     LAST_REPORT,  // Time of the last time we sent a report.
  48     LAST_REPORT_TIMER,  // Timer count of the last time we sent a report.
  49     DOOM_RECENT,  // The cache was partially cleared.
  50     UNUSED,  // Was: ga.js was evicted from the cache.
  51     MAX_COUNTER
  52   };
  53
  54   Stats();
  55   ~Stats();
  56
  57   // Initializes this object with |data| from disk.
  58   bool Init(void* data, int num_bytes, Addr address);
  59
  60   // Generates a size distribution histogram.
  61   void InitSizeHistogram();
  62
  63   // Returns the number of bytes needed to store the stats on disk.
  64   int StorageSize();
  65
  66   // Tracks changes to the stoage space used by an entry.
  67   void ModifyStorageStats(int32 old_size, int32 new_size);
  68
  69   // Tracks general events.
  70   void OnEvent(Counters an_event);
  71   void SetCounter(Counters counter, int64 value);
  72   int64 GetCounter(Counters counter) const;
  73
  74   void GetItems(StatsItems* items);
  75   int GetHitRatio() const;
  76   int GetResurrectRatio() const;
  77   void ResetRatios();
  78
  79   // Returns the lower bound of the space used by entries bigger than 512 KB.
  80   int GetLargeEntriesSize();
  81
  82   // Writes the stats into |data|, to be stored at the given cache address.
  83   // Returns the number of bytes copied.
  84   int SerializeStats(void* data, int num_bytes, Addr* address);
  85
  86   // Support for StatsHistograms. Together, these methods allow StatsHistograms
  87   // to take a snapshot of the data_sizes_ as the histogram data.
  88   int GetBucketRange(size_t i) const;
  89   void Snapshot(base::HistogramSamples* samples) const;
  90
  91  private:
  92   int GetStatsBucket(int32 size);
  93   int GetRatio(Counters hit, Counters miss) const;
  94
  95   Addr storage_addr_;
  96   int data_sizes_[kDataSizesLength];
  97   int64 counters_[MAX_COUNTER];
  98   StatsHistogram* size_histogram_;
  99
 100   DISALLOW_COPY_AND_ASSIGN(Stats);
 101 };
 102
 103 }  // namespace disk_cache
 104
 105 #endif  // NET_DISK_CACHE_STATS_H_