Loading metrics/README +33 −0 Original line number Diff line number Diff line Loading @@ -116,3 +116,36 @@ signals to or communicate in some alternative way with the metrics daemon. Then the metrics daemon needs to monitor for the relevant events and take appropriate action -- for example, aggregate data and send the histogram samples. ================================================================================ FAQ ================================================================================ Q. What should my histogram's |min| and |max| values be set at? A. You should set the values to a range that covers the vast majority of samples that would appear in the field. Note that samples below the |min| will still be collected in the underflow bucket and samples above the |max| will end up in the overflow bucket. Also, the reported mean of the data will be correct regardless of the range. Q. How many buckets should I use in my histogram? A. You should allocate as many buckets as necessary to perform proper analysis on the collected data. Note, however, that the memory allocated in Chrome for each histogram is proportional to the number of buckets. Therefore, it is strongly recommended to keep this number low (e.g., 50 is normal, while 100 is probably high). Q. When should I use an enumeration (linear) histogram vs. a regular (exponential) histogram? A. Enumeration histograms should really be used only for sampling enumerated events and, in some cases, percentages. Normally, you should use a regular histogram with exponential bucket layout that provides higher resolution at the low end of the range and lower resolution at the high end. Regular histograms are generally used for collecting performance data (e.g., timing, memory usage, power) as well as aggregated event counts. metrics/metrics_library.h +11 −0 Original line number Diff line number Diff line Loading @@ -38,6 +38,11 @@ class MetricsLibrary : public MetricsLibraryInterface { // |nbuckets| is the number of histogram buckets. // [0,min) is the implicit underflow bucket. // [|max|,infinity) is the implicit overflow bucket. // // Note that the memory allocated in Chrome for each histogram is // proportional to the number of buckets. Therefore, it is strongly // recommended to keep this number low (e.g., 50 is normal, while // 100 is high). bool SendToUMA(const std::string& name, int sample, int min, int max, int nbuckets); Loading @@ -50,6 +55,12 @@ class MetricsLibrary : public MetricsLibraryInterface { // |max| is the maximum value of the histogram samples. // 0 is the implicit underflow bucket. // [|max|,infinity) is the implicit overflow bucket. // // An enumaration histogram requires |max| + 1 number of // buckets. Note that the memory allocated in Chrome for each // histogram is proportional to the number of buckets. Therefore, it // is strongly recommended to keep this number low (e.g., 50 is // normal, while 100 is high). bool SendEnumToUMA(const std::string& name, int sample, int max); // Sends to Autotest and returns true on success. Loading Loading
metrics/README +33 −0 Original line number Diff line number Diff line Loading @@ -116,3 +116,36 @@ signals to or communicate in some alternative way with the metrics daemon. Then the metrics daemon needs to monitor for the relevant events and take appropriate action -- for example, aggregate data and send the histogram samples. ================================================================================ FAQ ================================================================================ Q. What should my histogram's |min| and |max| values be set at? A. You should set the values to a range that covers the vast majority of samples that would appear in the field. Note that samples below the |min| will still be collected in the underflow bucket and samples above the |max| will end up in the overflow bucket. Also, the reported mean of the data will be correct regardless of the range. Q. How many buckets should I use in my histogram? A. You should allocate as many buckets as necessary to perform proper analysis on the collected data. Note, however, that the memory allocated in Chrome for each histogram is proportional to the number of buckets. Therefore, it is strongly recommended to keep this number low (e.g., 50 is normal, while 100 is probably high). Q. When should I use an enumeration (linear) histogram vs. a regular (exponential) histogram? A. Enumeration histograms should really be used only for sampling enumerated events and, in some cases, percentages. Normally, you should use a regular histogram with exponential bucket layout that provides higher resolution at the low end of the range and lower resolution at the high end. Regular histograms are generally used for collecting performance data (e.g., timing, memory usage, power) as well as aggregated event counts.
metrics/metrics_library.h +11 −0 Original line number Diff line number Diff line Loading @@ -38,6 +38,11 @@ class MetricsLibrary : public MetricsLibraryInterface { // |nbuckets| is the number of histogram buckets. // [0,min) is the implicit underflow bucket. // [|max|,infinity) is the implicit overflow bucket. // // Note that the memory allocated in Chrome for each histogram is // proportional to the number of buckets. Therefore, it is strongly // recommended to keep this number low (e.g., 50 is normal, while // 100 is high). bool SendToUMA(const std::string& name, int sample, int min, int max, int nbuckets); Loading @@ -50,6 +55,12 @@ class MetricsLibrary : public MetricsLibraryInterface { // |max| is the maximum value of the histogram samples. // 0 is the implicit underflow bucket. // [|max|,infinity) is the implicit overflow bucket. // // An enumaration histogram requires |max| + 1 number of // buckets. Note that the memory allocated in Chrome for each // histogram is proportional to the number of buckets. Therefore, it // is strongly recommended to keep this number low (e.g., 50 is // normal, while 100 is high). bool SendEnumToUMA(const std::string& name, int sample, int max); // Sends to Autotest and returns true on success. Loading
