summaryrefslogtreecommitdiffstats
diff options
context:
space:
mode:
Diffstat
-rw-r--r--base/metrics/histogram.cc179
-rw-r--r--base/metrics/histogram.h43
-rw-r--r--base/metrics/histogram_unittest.cc25
-rw-r--r--chrome/common/metrics_helpers.cc12
-rw-r--r--net/disk_cache/stats_histogram.cc19
-rw-r--r--net/disk_cache/stats_histogram.h1
6 files changed, 206 insertions, 73 deletions
diff --git a/base/metrics/histogram.cc b/base/metrics/histogram.cc
index e94cef4..1d6f884 100644
--- a/base/metrics/histogram.cc
+++ b/base/metrics/histogram.cc
@@ -21,6 +21,53 @@
namespace base {
+// Static table of checksums for all possible 8 bit bytes.
+const uint32 Histogram::kCrcTable[256] = {0x0, 0x77073096L, 0xee0e612cL,
+0x990951baL, 0x76dc419L, 0x706af48fL, 0xe963a535L, 0x9e6495a3L, 0xedb8832L,
+0x79dcb8a4L, 0xe0d5e91eL, 0x97d2d988L, 0x9b64c2bL, 0x7eb17cbdL, 0xe7b82d07L,
+0x90bf1d91L, 0x1db71064L, 0x6ab020f2L, 0xf3b97148L, 0x84be41deL, 0x1adad47dL,
+0x6ddde4ebL, 0xf4d4b551L, 0x83d385c7L, 0x136c9856L, 0x646ba8c0L, 0xfd62f97aL,
+0x8a65c9ecL, 0x14015c4fL, 0x63066cd9L, 0xfa0f3d63L, 0x8d080df5L, 0x3b6e20c8L,
+0x4c69105eL, 0xd56041e4L, 0xa2677172L, 0x3c03e4d1L, 0x4b04d447L, 0xd20d85fdL,
+0xa50ab56bL, 0x35b5a8faL, 0x42b2986cL, 0xdbbbc9d6L, 0xacbcf940L, 0x32d86ce3L,
+0x45df5c75L, 0xdcd60dcfL, 0xabd13d59L, 0x26d930acL, 0x51de003aL, 0xc8d75180L,
+0xbfd06116L, 0x21b4f4b5L, 0x56b3c423L, 0xcfba9599L, 0xb8bda50fL, 0x2802b89eL,
+0x5f058808L, 0xc60cd9b2L, 0xb10be924L, 0x2f6f7c87L, 0x58684c11L, 0xc1611dabL,
+0xb6662d3dL, 0x76dc4190L, 0x1db7106L, 0x98d220bcL, 0xefd5102aL, 0x71b18589L,
+0x6b6b51fL, 0x9fbfe4a5L, 0xe8b8d433L, 0x7807c9a2L, 0xf00f934L, 0x9609a88eL,
+0xe10e9818L, 0x7f6a0dbbL, 0x86d3d2dL, 0x91646c97L, 0xe6635c01L, 0x6b6b51f4L,
+0x1c6c6162L, 0x856530d8L, 0xf262004eL, 0x6c0695edL, 0x1b01a57bL, 0x8208f4c1L,
+0xf50fc457L, 0x65b0d9c6L, 0x12b7e950L, 0x8bbeb8eaL, 0xfcb9887cL, 0x62dd1ddfL,
+0x15da2d49L, 0x8cd37cf3L, 0xfbd44c65L, 0x4db26158L, 0x3ab551ceL, 0xa3bc0074L,
+0xd4bb30e2L, 0x4adfa541L, 0x3dd895d7L, 0xa4d1c46dL, 0xd3d6f4fbL, 0x4369e96aL,
+0x346ed9fcL, 0xad678846L, 0xda60b8d0L, 0x44042d73L, 0x33031de5L, 0xaa0a4c5fL,
+0xdd0d7cc9L, 0x5005713cL, 0x270241aaL, 0xbe0b1010L, 0xc90c2086L, 0x5768b525L,
+0x206f85b3L, 0xb966d409L, 0xce61e49fL, 0x5edef90eL, 0x29d9c998L, 0xb0d09822L,
+0xc7d7a8b4L, 0x59b33d17L, 0x2eb40d81L, 0xb7bd5c3bL, 0xc0ba6cadL, 0xedb88320L,
+0x9abfb3b6L, 0x3b6e20cL, 0x74b1d29aL, 0xead54739L, 0x9dd277afL, 0x4db2615L,
+0x73dc1683L, 0xe3630b12L, 0x94643b84L, 0xd6d6a3eL, 0x7a6a5aa8L, 0xe40ecf0bL,
+0x9309ff9dL, 0xa00ae27L, 0x7d079eb1L, 0xf00f9344L, 0x8708a3d2L, 0x1e01f268L,
+0x6906c2feL, 0xf762575dL, 0x806567cbL, 0x196c3671L, 0x6e6b06e7L, 0xfed41b76L,
+0x89d32be0L, 0x10da7a5aL, 0x67dd4accL, 0xf9b9df6fL, 0x8ebeeff9L, 0x17b7be43L,
+0x60b08ed5L, 0xd6d6a3e8L, 0xa1d1937eL, 0x38d8c2c4L, 0x4fdff252L, 0xd1bb67f1L,
+0xa6bc5767L, 0x3fb506ddL, 0x48b2364bL, 0xd80d2bdaL, 0xaf0a1b4cL, 0x36034af6L,
+0x41047a60L, 0xdf60efc3L, 0xa867df55L, 0x316e8eefL, 0x4669be79L, 0xcb61b38cL,
+0xbc66831aL, 0x256fd2a0L, 0x5268e236L, 0xcc0c7795L, 0xbb0b4703L, 0x220216b9L,
+0x5505262fL, 0xc5ba3bbeL, 0xb2bd0b28L, 0x2bb45a92L, 0x5cb36a04L, 0xc2d7ffa7L,
+0xb5d0cf31L, 0x2cd99e8bL, 0x5bdeae1dL, 0x9b64c2b0L, 0xec63f226L, 0x756aa39cL,
+0x26d930aL, 0x9c0906a9L, 0xeb0e363fL, 0x72076785L, 0x5005713L, 0x95bf4a82L,
+0xe2b87a14L, 0x7bb12baeL, 0xcb61b38L, 0x92d28e9bL, 0xe5d5be0dL, 0x7cdcefb7L,
+0xbdbdf21L, 0x86d3d2d4L, 0xf1d4e242L, 0x68ddb3f8L, 0x1fda836eL, 0x81be16cdL,
+0xf6b9265bL, 0x6fb077e1L, 0x18b74777L, 0x88085ae6L, 0xff0f6a70L, 0x66063bcaL,
+0x11010b5cL, 0x8f659effL, 0xf862ae69L, 0x616bffd3L, 0x166ccf45L, 0xa00ae278L,
+0xd70dd2eeL, 0x4e048354L, 0x3903b3c2L, 0xa7672661L, 0xd06016f7L, 0x4969474dL,
+0x3e6e77dbL, 0xaed16a4aL, 0xd9d65adcL, 0x40df0b66L, 0x37d83bf0L, 0xa9bcae53L,
+0xdebb9ec5L, 0x47b2cf7fL, 0x30b5ffe9L, 0xbdbdf21cL, 0xcabac28aL, 0x53b39330L,
+0x24b4a3a6L, 0xbad03605L, 0xcdd70693L, 0x54de5729L, 0x23d967bfL, 0xb3667a2eL,
+0xc4614ab8L, 0x5d681b02L, 0x2a6f2b94L, 0xb40bbe37L, 0xc30c8ea1L, 0x5a05df1bL,
+0x2d02ef8dL,
+};
+
typedef Histogram::Count Count;
// static
@@ -38,7 +85,8 @@ scoped_refptr<Histogram> Histogram::FactoryGet(const std::string& name,
if (!StatisticsRecorder::FindHistogram(name, &histogram)) {
histogram = new Histogram(name, minimum, maximum, bucket_count);
- StatisticsRecorder::FindHistogram(name, &histogram);
+ histogram->InitializeBucketRange();
+ StatisticsRecorder::RegisterOrDiscardDuplicate(&histogram);
}
DCHECK_EQ(HISTOGRAM, histogram->histogram_type());
@@ -161,7 +209,7 @@ std::string Histogram::SerializeHistogramInfo(const Histogram& histogram,
pickle.WriteInt(histogram.declared_min());
pickle.WriteInt(histogram.declared_max());
pickle.WriteSize(histogram.bucket_count());
- pickle.WriteInt(histogram.range_checksum());
+ pickle.WriteUInt32(histogram.range_checksum());
pickle.WriteInt(histogram.histogram_type());
pickle.WriteInt(histogram.flags());
@@ -181,7 +229,7 @@ bool Histogram::DeserializeHistogramInfo(const std::string& histogram_info) {
int declared_min;
int declared_max;
size_t bucket_count;
- int range_checksum;
+ uint32 range_checksum;
int histogram_type;
int pickle_flags;
SampleSet sample;
@@ -191,7 +239,7 @@ bool Histogram::DeserializeHistogramInfo(const std::string& histogram_info) {
!pickle.ReadInt(&iter, &declared_min) ||
!pickle.ReadInt(&iter, &declared_max) ||
!pickle.ReadSize(&iter, &bucket_count) ||
- !pickle.ReadInt(&iter, &range_checksum) ||
+ !pickle.ReadUInt32(&iter, &range_checksum) ||
!pickle.ReadInt(&iter, &histogram_type) ||
!pickle.ReadInt(&iter, &pickle_flags) ||
!sample.Histogram::SampleSet::Deserialize(&iter, pickle)) {
@@ -252,18 +300,16 @@ Histogram::Inconsistencies Histogram::FindCorruption(
const SampleSet& snapshot) const {
int inconsistencies = NO_INCONSISTENCIES;
Sample previous_range = -1; // Bottom range is always 0.
- Sample checksum = 0;
int64 count = 0;
for (size_t index = 0; index < bucket_count(); ++index) {
count += snapshot.counts(index);
int new_range = ranges(index);
- checksum += new_range;
if (previous_range >= new_range)
inconsistencies |= BUCKET_ORDER_ERROR;
previous_range = new_range;
}
- if (checksum != range_checksum_)
+ if (!HasValidRangeChecksum())
inconsistencies |= RANGE_CHECKSUM_ERROR;
int64 delta64 = snapshot.redundant_count() - count;
@@ -328,6 +374,10 @@ bool Histogram::HasConstructorTimeDeltaArguments(TimeDelta minimum,
(bucket_count == bucket_count_));
}
+bool Histogram::HasValidRangeChecksum() const {
+ return CalculateRangeChecksum() == range_checksum_;
+}
+
Histogram::Histogram(const std::string& name, Sample minimum,
Sample maximum, size_t bucket_count)
: histogram_name_(name),
@@ -363,11 +413,6 @@ Histogram::~Histogram() {
// Just to make sure most derived class did this properly...
DCHECK(ValidateBucketRanges());
- DCHECK(HasValidRangeChecksum());
-}
-
-bool Histogram::PrintEmptyBucket(size_t index) const {
- return true;
}
// Calculate what range of values are held in each bucket.
@@ -405,6 +450,10 @@ void Histogram::InitializeBucketRange() {
DCHECK_EQ(bucket_count(), bucket_index);
}
+bool Histogram::PrintEmptyBucket(size_t index) const {
+ return true;
+}
+
size_t Histogram::BucketIndex(Sample value) const {
// Use simple binary search. This is very general, but there are better
// approaches if we knew that the buckets were linearly distributed.
@@ -478,6 +527,14 @@ bool Histogram::ValidateBucketRanges() const {
return true;
}
+uint32 Histogram::CalculateRangeChecksum() const {
+ DCHECK_EQ(ranges_.size(), bucket_count() + 1);
+ uint32 checksum = static_cast<uint32>(ranges_.size()); // Seed checksum.
+ for (size_t index = 0; index < bucket_count(); ++index)
+ checksum = Crc32(checksum, ranges(index));
+ return checksum;
+}
+
void Histogram::Initialize() {
sample_.Resize(*this);
if (declared_min_ < 1)
@@ -491,22 +548,42 @@ void Histogram::Initialize() {
DCHECK_LE(bucket_count_, maximal_bucket_count);
DCHECK_EQ(0, ranges_[0]);
ranges_[bucket_count_] = kSampleType_MAX;
- InitializeBucketRange();
- DCHECK(ValidateBucketRanges());
- StatisticsRecorder::Register(this);
-}
-
-bool Histogram::HasValidRangeChecksum() const {
- return CalculateRangeChecksum() == range_checksum_;
}
-Histogram::Sample Histogram::CalculateRangeChecksum() const {
- DCHECK_EQ(ranges_.size(), bucket_count() + 1);
- Sample checksum = 0;
- for (size_t index = 0; index < bucket_count(); ++index) {
- checksum += ranges(index);
+// We generate the CRC-32 using the low order bits to select whether to XOR in
+// the reversed polynomial 0xedb88320L. This is nice and simple, and allows us
+// to keep the quotient in a uint32. Since we're not concerned about the nature
+// of corruptions (i.e., we don't care about bit sequencing, since we are
+// handling memory changes, which are more grotesque) so we don't bother to
+// get the CRC correct for big-endian vs little-ending calculations. All we
+// need is a nice hash, that tends to depend on all the bits of the sample, with
+// very little chance of changes in one place impacting changes in another
+// place.
+uint32 Histogram::Crc32(uint32 sum, Histogram::Sample range) {
+ const bool kUseRealCrc = true; // TODO(jar): Switch to false and watch stats.
+ if (kUseRealCrc) {
+ union {
+ Histogram::Sample range;
+ unsigned char bytes[sizeof(Histogram::Sample)];
+ } converter;
+ converter.range = range;
+ for (size_t i = 0; i < sizeof(converter); ++i)
+ sum = kCrcTable[(sum & 0xff) ^ converter.bytes[i]] ^ (sum >> 8);
+ } else {
+ // Use hash techniques provided in ReallyFastHash, except we don't care
+ // about "avalanching" (which would worsten the hash, and add collisions),
+ // and we don't care about edge cases since we have an even number of bytes.
+ union {
+ Histogram::Sample range;
+ uint16 ints[sizeof(Histogram::Sample) / 2];
+ } converter;
+ DCHECK_EQ(sizeof(Histogram::Sample), sizeof(converter));
+ converter.range = range;
+ sum += converter.ints[0];
+ sum = (sum << 16) ^ sum ^ (static_cast<uint32>(converter.ints[1]) << 11);
+ sum += sum >> 11;
}
- return checksum;
+ return sum;
}
//------------------------------------------------------------------------------
@@ -710,8 +787,11 @@ scoped_refptr<Histogram> LinearHistogram::FactoryGet(const std::string& name,
maximum = kSampleType_MAX - 1;
if (!StatisticsRecorder::FindHistogram(name, &histogram)) {
- histogram = new LinearHistogram(name, minimum, maximum, bucket_count);
- StatisticsRecorder::FindHistogram(name, &histogram);
+ LinearHistogram* linear_histogram =
+ new LinearHistogram(name, minimum, maximum, bucket_count);
+ linear_histogram->InitializeBucketRange();
+ histogram = linear_histogram;
+ StatisticsRecorder::RegisterOrDiscardDuplicate(&histogram);
}
DCHECK_EQ(LINEAR_HISTOGRAM, histogram->histogram_type());
@@ -746,8 +826,6 @@ LinearHistogram::LinearHistogram(const std::string& name,
Sample maximum,
size_t bucket_count)
: Histogram(name, minimum >= 1 ? minimum : 1, maximum, bucket_count) {
- InitializeBucketRange();
- DCHECK(ValidateBucketRanges());
}
LinearHistogram::LinearHistogram(const std::string& name,
@@ -757,9 +835,6 @@ LinearHistogram::LinearHistogram(const std::string& name,
: Histogram(name, minimum >= TimeDelta::FromMilliseconds(1) ?
minimum : TimeDelta::FromMilliseconds(1),
maximum, bucket_count) {
- // Do a "better" (different) job at init than a base classes did...
- InitializeBucketRange();
- DCHECK(ValidateBucketRanges());
}
void LinearHistogram::InitializeBucketRange() {
@@ -805,8 +880,10 @@ scoped_refptr<Histogram> BooleanHistogram::FactoryGet(const std::string& name,
scoped_refptr<Histogram> histogram(NULL);
if (!StatisticsRecorder::FindHistogram(name, &histogram)) {
- histogram = new BooleanHistogram(name);
- StatisticsRecorder::FindHistogram(name, &histogram);
+ BooleanHistogram* boolean_histogram = new BooleanHistogram(name);
+ boolean_histogram->InitializeBucketRange();
+ histogram = boolean_histogram;
+ StatisticsRecorder::RegisterOrDiscardDuplicate(&histogram);
}
DCHECK_EQ(BOOLEAN_HISTOGRAM, histogram->histogram_type());
@@ -850,8 +927,10 @@ scoped_refptr<Histogram> CustomHistogram::FactoryGet(
DCHECK_LT(ranges.back(), kSampleType_MAX);
if (!StatisticsRecorder::FindHistogram(name, &histogram)) {
- histogram = new CustomHistogram(name, ranges);
- StatisticsRecorder::FindHistogram(name, &histogram);
+ CustomHistogram* custom_histogram = new CustomHistogram(name, ranges);
+ custom_histogram->InitializedCustomBucketRange(ranges);
+ histogram = custom_histogram;
+ StatisticsRecorder::RegisterOrDiscardDuplicate(&histogram);
}
DCHECK_EQ(histogram->histogram_type(), CUSTOM_HISTOGRAM);
@@ -871,16 +950,15 @@ CustomHistogram::CustomHistogram(const std::string& name,
custom_ranges.size()) {
DCHECK_GT(custom_ranges.size(), 1u);
DCHECK_EQ(custom_ranges[0], 0);
- ranges_vector_ = &custom_ranges;
- InitializeBucketRange();
- ranges_vector_ = NULL;
- DCHECK(ValidateBucketRanges());
}
-void CustomHistogram::InitializeBucketRange() {
- DCHECK_LE(ranges_vector_->size(), bucket_count());
- for (size_t index = 0; index < ranges_vector_->size(); ++index)
- SetBucketRange(index, (*ranges_vector_)[index]);
+void CustomHistogram::InitializedCustomBucketRange(
+ const std::vector<Sample>& custom_ranges) {
+ DCHECK_GT(custom_ranges.size(), 1u);
+ DCHECK_EQ(custom_ranges[0], 0);
+ DCHECK_LE(custom_ranges.size(), bucket_count());
+ for (size_t index = 0; index < custom_ranges.size(); ++index)
+ SetBucketRange(index, custom_ranges[index]);
ResetRangeChecksum();
}
@@ -945,16 +1023,21 @@ bool StatisticsRecorder::IsActive() {
// was passed to us, decremented it when we returned, and the instance would be
// destroyed before assignment (when value was returned by new).
// static
-void StatisticsRecorder::Register(Histogram* histogram) {
+void StatisticsRecorder::RegisterOrDiscardDuplicate(
+ scoped_refptr<Histogram>* histogram) {
+ DCHECK((*histogram)->HasValidRangeChecksum());
if (lock_ == NULL)
return;
base::AutoLock auto_lock(*lock_);
if (!histograms_)
return;
- const std::string name = histogram->histogram_name();
+ const std::string name = (*histogram)->histogram_name();
+ HistogramMap::iterator it = histograms_->find(name);
// Avoid overwriting a previous registration.
- if (histograms_->end() == histograms_->find(name))
- (*histograms_)[name] = histogram;
+ if (histograms_->end() == it)
+ (*histograms_)[name] = *histogram;
+ else
+ *histogram = it->second;
}
// static
diff --git a/base/metrics/histogram.h b/base/metrics/histogram.h
index 372dae5..347932a 100644
--- a/base/metrics/histogram.h
+++ b/base/metrics/histogram.h
@@ -411,7 +411,7 @@ class Histogram : public base::RefCountedThreadSafe<Histogram> {
Sample declared_min() const { return declared_min_; }
Sample declared_max() const { return declared_max_; }
virtual Sample ranges(size_t i) const;
- Sample range_checksum() const { return range_checksum_; }
+ uint32 range_checksum() const { return range_checksum_; }
virtual size_t bucket_count() const;
// Snapshot the current complete set of sample data.
// Override with atomic/locked snapshot if needed.
@@ -423,6 +423,8 @@ class Histogram : public base::RefCountedThreadSafe<Histogram> {
virtual bool HasConstructorTimeDeltaArguments(TimeDelta minimum,
TimeDelta maximum,
size_t bucket_count);
+ // Return true iff the range_checksum_ matches current ranges_ vector.
+ bool HasValidRangeChecksum() const;
protected:
friend class base::RefCountedThreadSafe<Histogram>;
@@ -433,14 +435,15 @@ class Histogram : public base::RefCountedThreadSafe<Histogram> {
virtual ~Histogram();
+ // Initialize ranges_ mapping.
+ void InitializeBucketRange();
+
// Method to override to skip the display of the i'th bucket if it's empty.
virtual bool PrintEmptyBucket(size_t index) const;
//----------------------------------------------------------------------------
// Methods to override to create histogram with different bucket widths.
//----------------------------------------------------------------------------
- // Initialize ranges_ mapping.
- virtual void InitializeBucketRange();
// Find bucket to increment for sample value.
virtual size_t BucketIndex(Sample value) const;
// Get normalized size, relative to the ranges_[i].
@@ -469,18 +472,20 @@ class Histogram : public base::RefCountedThreadSafe<Histogram> {
// values relate properly to the declared_min_ and declared_max_)..
bool ValidateBucketRanges() const;
+ virtual uint32 CalculateRangeChecksum() const;
+
private:
// Allow tests to corrupt our innards for testing purposes.
FRIEND_TEST(HistogramTest, CorruptBucketBounds);
FRIEND_TEST(HistogramTest, CorruptSampleCounts);
+ FRIEND_TEST(HistogramTest, Crc32SampleHash);
+ FRIEND_TEST(HistogramTest, Crc32TableTest);
// Post constructor initialization.
void Initialize();
- // Return true iff the range_checksum_ matches current ranges_ vector.
- bool HasValidRangeChecksum() const;
-
- Sample CalculateRangeChecksum() const;
+ // Checksum function for accumulating range values into a checksum.
+ static uint32 Crc32(uint32 sum, Sample range);
//----------------------------------------------------------------------------
// Helpers for emitting Ascii graphic. Each method appends data to output.
@@ -508,6 +513,9 @@ class Histogram : public base::RefCountedThreadSafe<Histogram> {
std::string* output) const;
//----------------------------------------------------------------------------
+ // Table for generating Crc32 values.
+ static const uint32 kCrcTable[256];
+ //----------------------------------------------------------------------------
// Invariant values set at/near construction time
// ASCII version of original name given to the constructor. All identically
@@ -526,10 +534,10 @@ class Histogram : public base::RefCountedThreadSafe<Histogram> {
// The dimension of ranges_ is bucket_count + 1.
Ranges ranges_;
- // For redundancy, we store the sum of all the sample ranges when ranges are
- // generated. If ever there is ever a difference, then the histogram must
+ // For redundancy, we store a checksum of all the sample ranges when ranges
+ // are generated. If ever there is ever a difference, then the histogram must
// have been corrupted.
- Sample range_checksum_;
+ uint32 range_checksum_;
// Finally, provide the state that changes with the addition of each new
// sample.
@@ -569,7 +577,7 @@ class LinearHistogram : public Histogram {
TimeDelta maximum, size_t bucket_count);
// Initialize ranges_ mapping.
- virtual void InitializeBucketRange();
+ void InitializeBucketRange();
virtual double GetBucketSize(Count current, size_t i) const;
// If we have a description for a bucket, then return that. Otherwise
@@ -625,13 +633,9 @@ class CustomHistogram : public Histogram {
const std::vector<Sample>& custom_ranges);
// Initialize ranges_ mapping.
- virtual void InitializeBucketRange();
+ void InitializedCustomBucketRange(const std::vector<Sample>& custom_ranges);
virtual double GetBucketSize(Count current, size_t i) const;
- private:
- // Temporary pointer used during construction/initialization, and then NULLed.
- const std::vector<Sample>* ranges_vector_;
-
DISALLOW_COPY_AND_ASSIGN(CustomHistogram);
};
@@ -651,8 +655,11 @@ class StatisticsRecorder {
// Find out if histograms can now be registered into our list.
static bool IsActive();
- // Register, or add a new histogram to the collection of statistics.
- static void Register(Histogram* histogram);
+ // Register, or add a new histogram to the collection of statistics. If an
+ // identically named histogram is already registered, then the argument
+ // |histogram| will be replaced by the previously registered value, discarding
+ // the referenced argument.
+ static void RegisterOrDiscardDuplicate(scoped_refptr<Histogram>* histogram);
// Methods for printing histograms. Only histograms which have query as
// a substring are written to output (an empty string will process all
diff --git a/base/metrics/histogram_unittest.cc b/base/metrics/histogram_unittest.cc
index b9c51ad..afa69a6 100644
--- a/base/metrics/histogram_unittest.cc
+++ b/base/metrics/histogram_unittest.cc
@@ -348,7 +348,8 @@ TEST(HistogramTest, CorruptBucketBounds) {
EXPECT_EQ(0, histogram->FindCorruption(snapshot)); // No default corruption.
std::swap(histogram->ranges_[1], histogram->ranges_[2]);
- EXPECT_EQ(Histogram::BUCKET_ORDER_ERROR, histogram->FindCorruption(snapshot));
+ EXPECT_EQ(Histogram::BUCKET_ORDER_ERROR | Histogram::RANGE_CHECKSUM_ERROR,
+ histogram->FindCorruption(snapshot));
std::swap(histogram->ranges_[1], histogram->ranges_[2]);
EXPECT_EQ(0, histogram->FindCorruption(snapshot));
@@ -357,8 +358,30 @@ TEST(HistogramTest, CorruptBucketBounds) {
EXPECT_EQ(Histogram::RANGE_CHECKSUM_ERROR,
histogram->FindCorruption(snapshot));
+ // Show that two simple changes don't offset each other
+ --histogram->ranges_[4];
+ EXPECT_EQ(Histogram::RANGE_CHECKSUM_ERROR,
+ histogram->FindCorruption(snapshot));
+
// Repair histogram so that destructor won't DCHECK().
--histogram->ranges_[3];
+ ++histogram->ranges_[4];
+}
+
+// Table was generated similarly to sample code for CRC-32 given on:
+// http://www.w3.org/TR/PNG/#D-CRCAppendix.
+TEST(HistogramTest, Crc32TableTest) {
+ for (int i = 0; i < 256; ++i) {
+ uint32 checksum = i;
+ for (int j = 0; j < 8; ++j) {
+ const uint32 kReversedPolynomial = 0xedb88320L;
+ if (checksum & 1)
+ checksum = kReversedPolynomial ^ (checksum >> 1);
+ else
+ checksum >>= 1;
+ }
+ EXPECT_EQ(Histogram::kCrcTable[i], checksum);
+ }
}
} // namespace base
diff --git a/chrome/common/metrics_helpers.cc b/chrome/common/metrics_helpers.cc
index 644df78..c043846 100644
--- a/chrome/common/metrics_helpers.cc
+++ b/chrome/common/metrics_helpers.cc
@@ -531,6 +531,18 @@ void HistogramSender::TransmitHistogram(const Histogram& histogram) {
const std::string& histogram_name = histogram.histogram_name();
int corruption = histogram.FindCorruption(snapshot);
+
+ // Crash if we detect that our histograms have been overwritten. This may be
+ // a fair distance from the memory smasher, but we hope to correlate these
+ // crashes with other events, such as plugins, or usage patterns, etc.
+ if (Histogram::BUCKET_ORDER_ERROR & corruption) {
+ // The checksum should have caught this, so crash separately if it didn't.
+ CHECK_NE(0, Histogram::RANGE_CHECKSUM_ERROR & corruption);
+ CHECK(false); // Crash for the bucket order corruption.
+ }
+ // Checksum corruption might not have caused order corruption.
+ CHECK_EQ(0, Histogram::RANGE_CHECKSUM_ERROR & corruption);
+
if (corruption) {
NOTREACHED();
InconsistencyDetected(corruption);
diff --git a/net/disk_cache/stats_histogram.cc b/net/disk_cache/stats_histogram.cc
index 39c9056..d859899 100644
--- a/net/disk_cache/stats_histogram.cc
+++ b/net/disk_cache/stats_histogram.cc
@@ -32,12 +32,11 @@ scoped_refptr<StatsHistogram> StatsHistogram::StatsHistogramFactoryGet(
if (StatisticsRecorder::FindHistogram(name, &histogram)) {
DCHECK(histogram.get() != NULL);
} else {
- histogram = new StatsHistogram(name, minimum, maximum, bucket_count);
- scoped_refptr<Histogram> registered_histogram(NULL);
- StatisticsRecorder::FindHistogram(name, &registered_histogram);
- if (registered_histogram.get() != NULL &&
- registered_histogram.get() != histogram.get())
- histogram = registered_histogram;
+ StatsHistogram* stats_histogram = new StatsHistogram(name, minimum, maximum,
+ bucket_count);
+ stats_histogram->InitializeBucketRange();
+ histogram = stats_histogram;
+ StatisticsRecorder::RegisterOrDiscardDuplicate(&histogram);
}
DCHECK(HISTOGRAM == histogram->histogram_type());
@@ -48,6 +47,9 @@ scoped_refptr<StatsHistogram> StatsHistogram::StatsHistogramFactoryGet(
Histogram* temp_histogram = histogram.get();
StatsHistogram* temp_stats_histogram =
static_cast<StatsHistogram*>(temp_histogram);
+ // Validate upcast by seeing that we're probably providing the checksum.
+ CHECK_EQ(temp_stats_histogram->StatsHistogram::CalculateRangeChecksum(),
+ temp_stats_histogram->CalculateRangeChecksum());
scoped_refptr<StatsHistogram> return_histogram(temp_stats_histogram);
return return_histogram;
}
@@ -91,5 +93,10 @@ Histogram::Inconsistencies StatsHistogram::FindCorruption(
return NO_INCONSISTENCIES; // This class won't monitor inconsistencies.
}
+uint32 StatsHistogram::CalculateRangeChecksum() const {
+ // We don't calculate checksums, so at least establish a unique constant.
+ const uint32 kStatsHistogramChecksum = 0x0cecce;
+ return kStatsHistogramChecksum;
+}
} // namespace disk_cache
diff --git a/net/disk_cache/stats_histogram.h b/net/disk_cache/stats_histogram.h
index 499784c..249327c 100644
--- a/net/disk_cache/stats_histogram.h
+++ b/net/disk_cache/stats_histogram.h
@@ -45,6 +45,7 @@ class StatsHistogram : public base::Histogram {
virtual size_t bucket_count() const;
virtual void SnapshotSample(SampleSet* sample) const;
virtual Inconsistencies FindCorruption(const SampleSet& snapshot) const;
+ virtual uint32 CalculateRangeChecksum() const;
private:
bool init_;
generated by cgit v1.1 at 2025-01-20 08:21:04 +0000