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

2 files changed, 14 insertions, 13 deletions

diff --git a/base/histogram.cc b/base/histogram.cc
index b4dede7..19dcf83 100644
--- a/base/histogram.cc
+++ b/base/histogram.cc
@@ -99,8 +99,8 @@ void Histogram::WriteAscii(bool graph_it, const std::string& newline,
 
   // Calculate space needed to print bucket range numbers.  Leave room to print
   // nearly the largest bucket range without sliding over the histogram.
-  size_t largest_non_empty_bucket = bucket_count_ - 1;
-  while (0 == sample_.counts(largest_non_empty_bucket)) {
+  size_t largest_non_empty_bucket = bucket_count() - 1;
+  while (0 == snapshot.counts(largest_non_empty_bucket)) {
     if (0 == largest_non_empty_bucket)
       break;  // All buckets are empty.
     largest_non_empty_bucket--;
@@ -108,7 +108,7 @@ void Histogram::WriteAscii(bool graph_it, const std::string& newline,
 
   // Calculate largest print width needed for any of our bucket range displays.
   size_t print_width = 1;
-  for (size_t i = 0; i < bucket_count_; ++i) {
+  for (size_t i = 0; i < bucket_count(); ++i) {
     if (snapshot.counts(i)) {
       size_t width = GetAsciiBucketRange(i).size() + 1;
       if (width > print_width)
@@ -119,14 +119,14 @@ void Histogram::WriteAscii(bool graph_it, const std::string& newline,
   int64 remaining = sample_count;
   int64 past = 0;
   // Output the actual histogram graph.
-  for (size_t i = 0; i < bucket_count_; i++) {
+  for (size_t i = 0; i < bucket_count(); i++) {
     Count current = snapshot.counts(i);
     if (!current && !PrintEmptyBucket(i))
       continue;
     remaining -= current;
     StringAppendF(output, "%#*s ", print_width, GetAsciiBucketRange(i).c_str());
-    if (0 == current && i < bucket_count_ - 1 && 0 == snapshot.counts(i + 1)) {
-      while (i < bucket_count_ - 1 && 0 == snapshot.counts(i + 1))
+    if (0 == current && i < bucket_count() - 1 && 0 == snapshot.counts(i + 1)) {
+      while (i < bucket_count() - 1 && 0 == snapshot.counts(i + 1))
         i++;
       output->append("... ");
       output->append(newline);
@@ -159,7 +159,7 @@ void Histogram::Initialize() {
   if (declared_max_ >= kSampleType_MAX)
     declared_max_ = kSampleType_MAX - 1;
   DCHECK(declared_min_ > 0);  // We provide underflow bucket.
-  DCHECK(declared_min_ < declared_max_);
+  DCHECK(declared_min_ <= declared_max_);
   DCHECK(1 < bucket_count_);
   size_t maximal_bucket_count = declared_max_ - declared_min_ + 2;
   DCHECK(bucket_count_ <= maximal_bucket_count);
@@ -275,7 +275,7 @@ void Histogram::SetBucketRange(size_t i, Sample value) {
 
 double Histogram::GetPeakBucketSize(const SampleSet& snapshot) const {
   double max = 0;
-  for (size_t i = 0; i < bucket_count_ ; i++) {
+  for (size_t i = 0; i < bucket_count() ; i++) {
     double current_size = GetBucketSize(snapshot.counts(i), i);
     if (current_size > max)
       max = current_size;
@@ -322,9 +322,9 @@ void Histogram::WriteAsciiBucketContext(const int64 past,
 const std::string Histogram::GetAsciiBucketRange(size_t i) const {
   std::string result;
   if (kHexRangePrintingFlag & flags_)
-    StringAppendF(&result, "%#x", ranges_[i]);
+    StringAppendF(&result, "%#x", ranges(i));
   else
-    StringAppendF(&result, "%d", ranges_[i]);
+    StringAppendF(&result, "%d", ranges(i));
   return result;
 }
 
diff --git a/base/histogram.h b/base/histogram.h
index 678cbf6..a2672e0 100644
--- a/base/histogram.h
+++ b/base/histogram.h
@@ -177,7 +177,7 @@ class Histogram : public StatsRate {
     void Add(const SampleSet& other);
     void Subtract(const SampleSet& other);
 
-   private:
+   protected:
     // Actual histogram data is stored in buckets, showing the count of values
     // that fit into each bucket.
     Counts counts_;
@@ -208,6 +208,7 @@ class Histogram : public StatsRate {
   // 0x1 Currently used to mark this histogram to be recorded by UMA..
   // 0x8000 means print ranges in hex.
   void SetFlags(int flags) { flags_ |= flags; }
+  void ClearFlags(int flags) { flags_ &= ~flags; }
   int flags() const { return flags_; }
 
   //----------------------------------------------------------------------------
@@ -216,8 +217,8 @@ class Histogram : public StatsRate {
   const std::string histogram_name() const { return histogram_name_; }
   Sample declared_min() const { return declared_min_; }
   Sample declared_max() const { return declared_max_; }
-  Sample ranges(size_t i) const { return ranges_[i];}
-  size_t bucket_count() const { return bucket_count_; }
+  virtual Sample ranges(size_t i) const { return ranges_[i];}
+  virtual size_t bucket_count() const { return bucket_count_; }
   // Snapshot the current complete set of sample data.
   // Override with atomic/locked snapshot if needed.
   virtual void SnapshotSample(SampleSet* sample) const;