Fixes to latency histogram: Make it multi thread + correct average calculation

1 files changed, 47 insertions, 26 deletions

diff --git a/src/time_histogram.h b/src/time_histogram.h
index e733c65f..9bdf2c93 100755
--- a/src/time_histogram.h
+++ b/src/time_histogram.h
@@ -2,11 +2,12 @@
 #define C_TIME_HISTOGRAM_H
 /*
  Hanoh Haim
+ Ido Barnea
  Cisco Systems, Inc.
 */
 
 /*
-Copyright (c) 2015-2015 Cisco Systems, Inc.
+Copyright (c) 2015-2016 Cisco Systems, Inc.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -29,6 +30,35 @@ limitations under the License.
 #include "mbuf.h"
 #include <string>
 
+class CTimeHistogramPerPeriodData {
+ public:
+    void reset() {
+        m_sum = 0;
+        m_cnt = 0;
+        m_cnt_high = 0;
+        m_max = 0;
+    }
+    void inc_cnt() {m_cnt++;}
+    void inc_high_cnt() {m_cnt_high++;}
+    void update_max(dsec_t dt) {
+        if (dt > m_max)
+            m_max = dt;
+    }
+    void update_sum(dsec_t dt) {
+        m_sum += dt * 1000000;
+    }
+    inline uint64_t get_sum() {return m_sum;}
+    inline uint64_t get_cnt() {return m_cnt;}
+    inline uint64_t get_high_cnt() {return m_cnt_high;}
+    inline dsec_t get_max() {return m_max;}
+    inline dsec_t get_max_usec() {return m_max * 1000000;}
+
+ private:
+    uint64_t m_sum; // Sum of samples
+    uint64_t m_cnt;  // Number of samples
+    uint64_t m_cnt_high;  // Number of samples above configured threshold
+    dsec_t   m_max;  // Max sample
+};
 
 class CTimeHistogram {
 public:
@@ -43,50 +73,41 @@ public:
     bool Add(dsec_t dt);
     void Dump(FILE *fd);
     void DumpWinMax(FILE *fd);
-    /* should be called each 1 sec */
+    /* should be called once each sampling period */
     void update();
     dsec_t  get_average_latency();
     /* get average of total data */
-    dsec_t get_total_average();
-
-
     dsec_t  get_max_latency(){
         return (get_usec(m_max_dt));
     }
-
     dsec_t  get_max_latency_last_update(){
-        return ( get_usec(m_max_win_last_dt) );
+        CTimeHistogramPerPeriodData &period_elem = m_period_data[get_read_period_index()];
+        return period_elem.get_max_usec();
     }
-
     void  dump_json(std::string name,std::string & json );
 
-
 private:
     uint32_t get_usec(dsec_t d);
     double  get_cur_average();
-    void  update_average();
-
-    double get_base_usec(int j,int i){
-        double base=pow(10.0,(double)j+1.0);
-        return ( base * ((double)i+1.0) );
+    void  update_average(CTimeHistogramPerPeriodData &period_elem);
+    inline uint8_t get_read_period_index() {
+        if (m_period == 0)
+            return 1;
+        else
+            return 0;
     }
 
-public:
+private:
     dsec_t   m_min_delta;/* set to 10usec*/
-    uint64_t m_cnt;
-    uint64_t m_high_cnt;
-    dsec_t   m_max_dt;
-    dsec_t   m_max_win_dt;
-    dsec_t   m_max_win_last_dt;
+    // One element collects data for current period, other is saved for sending report.
+    // Each period we switch between the two
+    CTimeHistogramPerPeriodData m_period_data[2];
+    uint8_t m_period; // 0 or 1 according to m_period_data element we currently use
+    dsec_t   m_max_dt;  // Total maximum latency
     dsec_t   m_average; /* moving average */
-
     uint32_t m_win_cnt;
-    dsec_t   m_max_ar[HISTOGRAM_QUEUE_SIZE];
-
+    dsec_t   m_max_ar[HISTOGRAM_QUEUE_SIZE]; // Array of maximum latencies for previous periods
     uint64_t m_hcnt[HISTOGRAM_SIZE_LOG][HISTOGRAM_SIZE] __rte_cache_aligned ;
-    uint64_t m_hcnt_shadow[HISTOGRAM_SIZE_LOG][HISTOGRAM_SIZE] __rte_cache_aligned ; // this this contorl side 
-    uint64_t m_cnt_shadow;
-    uint64_t m_high_cnt_shadow;
 };
 
 #endif