Add a basic exact linear macro. Ends up being the same as enum, but making it explicit will make ou…

base/metrics/histogram_macros.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef BASE_METRICS_HISTOGRAM_MACROS_H_
 #define BASE_METRICS_HISTOGRAM_MACROS_H_
 
 #include "base/metrics/histogram.h"
 #include "base/metrics/histogram_macros_internal.h"
 #include "base/metrics/histogram_macros_local.h"
@@ skipping 35 matching lines @@
 // Histogram for boolean values.
 
 // Sample usage:
 //   UMA_HISTOGRAM_BOOLEAN("Histogram.Boolean", bool);
 #define UMA_HISTOGRAM_BOOLEAN(name, sample)                                    \
     STATIC_HISTOGRAM_POINTER_BLOCK(name, AddBoolean(sample),                   \
         base::BooleanHistogram::FactoryGet(name,                               \
             base::HistogramBase::kUmaTargetedHistogramFlag))
 
 //------------------------------------------------------------------------------
-// Percentage histograms.
+// Linear histograms.
 
 // All of these macros must be called with |name| as a runtime constant.
 
+// Used for capturing integer data with a linear bucketing scheme. This can be
+// used when you want the exact value of some small numeric count, with a max of
+// 100 or less. If you need to capture a range of greater than 100, we recommend
+// the use of the COUNT histograms below.
+
+// Sample usage:
+//   UMA_HISTOGRAM_EXACT_LINEAR("Histogram.Linear", count, 10);
+#define UMA_HISTOGRAM_EXACT_LINEAR(name, sample, value_max)                    \
+    UMA_HISTOGRAM_ENUMERATION(name, sample, value_max)

[Mark P, 2016/10/03 17:42:29]

Should we make this value_max+1 to better detect corruption (corrupted data will
fall into the overflow bucket, which will not overlap a real bucket)?

[rkaplow, 2016/10/03 19:19:44]

sure, that sounds good, although we do want to do a better job of this more
systematically (as per the bug I filed). Made the adjustment here though

+
+

[Mark P, 2016/10/03 17:42:29]

optional nit: remove one black line

 // Used for capturing basic percentages. This will be 100 buckets of size 1.
 
 // Sample usage:
 //   UMA_HISTOGRAM_PERCENTAGE("Histogram.Percent", percent_as_int);
-#define UMA_HISTOGRAM_PERCENTAGE(name, under_one_hundred)                      \
-    UMA_HISTOGRAM_ENUMERATION(name, under_one_hundred, 101)
-
+#define UMA_HISTOGRAM_PERCENTAGE(name, percent_as_int)                         \
+    UMA_HISTOGRAM_ENUMERATION(name, percent_as_int, 101)
 
 //------------------------------------------------------------------------------
 // Count histograms. These are used for collecting numeric data. Note that we
 // have macros for more specialized use cases below (memory, time, percentages).
 
 // The number suffixes here refer to the max size of the sample, i.e. COUNT_1000
 // will be able to collect samples of counts up to 1000. The default number of
 // buckets in all default macros is 50. We recommend erring on the side of too
 // large a range versus too short a range.
 // These macros default to exponential histograms - i.e. the lengths of the
@@ skipping 33 matching lines @@
 // buckets. Min values should be >=1 as emitted 0s will still go into the
 // underflow bucket.
 
 // Sample usage:
 //   UMA_HISTOGRAM_CUSTOM_COUNTS("My.Histogram", 1, 100000000, 100);
 #define UMA_HISTOGRAM_CUSTOM_COUNTS(name, sample, min, max, bucket_count)      \
     INTERNAL_HISTOGRAM_CUSTOM_COUNTS_WITH_FLAG(                                \
         name, sample, min, max, bucket_count,                                  \
         base::HistogramBase::kUmaTargetedHistogramFlag)
 
-
 //------------------------------------------------------------------------------
 // Timing histograms. These are used for collecting timing data (generally
 // latencies).
 
 // These macros create exponentially sized histograms (lengths of the bucket
 // ranges exponentially increase as the sample range increases). The input
 // sample is a base::TimeDelta. The output data is measured in ms granularity.
 // All of these macros must be called with |name| as a runtime constant.
 
 // Sample usage:
@@ skipping 116 matching lines @@
 // |custom_ranges|. See comments above CustomRanges::FactoryGet about the
 // requirement of |custom_ranges|. You can use the helper function
 // CustomHistogram::ArrayToCustomRanges to transform a C-style array of valid
 // sample values to a std::vector<int>.
 #define UMA_HISTOGRAM_CUSTOM_ENUMERATION(name, sample, custom_ranges)          \
     STATIC_HISTOGRAM_POINTER_BLOCK(name, Add(sample),                          \
         base::CustomHistogram::FactoryGet(name, custom_ranges,                 \
             base::HistogramBase::kUmaTargetedHistogramFlag))
 
 #endif  // BASE_METRICS_HISTOGRAM_MACROS_H_