Use histograms to send interesting parts of the disk cache statistics.

Most of this CL deals with a derived implementation of histograms that just
queries the size stats already generated by the disk cache. The exact number
of buckets, and their distribution, is controlled directly by the new class and
the disk cache stats code.

Review URL: http://codereview.chromium.org/3069

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@2580 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 33 insertions, 0 deletions

diff --git a/net/disk_cache/stats.cc b/net/disk_cache/stats.cc
index d57a0bb..83448d5 100644
--- a/net/disk_cache/stats.cc
+++ b/net/disk_cache/stats.cc
@@ -120,6 +120,8 @@ bool Stats::Init(BackendImpl* backend, uint32* storage_addr) {
 
   storage_addr_ = address.value();
   backend_ = backend;
+  size_histogram_.reset(new StatsHistogram(L"DiskCache.SizeStats"));
+  size_histogram_->Init(this);
 
   memcpy(data_sizes_, stats.data_sizes, sizeof(data_sizes_));
   memcpy(counters_, stats.counters, sizeof(counters_));
@@ -184,6 +186,37 @@ int Stats::GetStatsBucket(int32 size) {
   return result;
 }
 
+int Stats::GetBucketRange(size_t i) const {
+  if (i < 2)
+    return static_cast<int>(1024 * i);
+
+  if (i < 12)
+    return static_cast<int>(2048 * (i - 1));
+
+  if (i < 17)
+    return static_cast<int>(4096 * (i - 11)) + 20 * 1024;
+
+  int n = 64 * 1024;
+  if (i > static_cast<size_t>(kDataSizesLength)) {
+    NOTREACHED();
+    i = kDataSizesLength;
+  }
+
+  i -= 17;
+  n <<= i;
+  return n;
+}
+
+void Stats::Snapshot(StatsHistogram::StatsSamples* samples) const {
+  samples->GetCounts()->resize(kDataSizesLength);
+  for (int i = 0; i < kDataSizesLength; i++) {
+    int count = data_sizes_[i];
+    if (count < 0)
+      count = 0;
+    samples->GetCounts()->at(i) = count;
+  }
+}
+
 void Stats::ModifyStorageStats(int32 old_size, int32 new_size) {
   // We keep a counter of the data block size on an array where each entry is
   // the adjusted log base 2 of the size. The first entry counts blocks of 256