headers/private/kernel/load_tracking.h

   1 /*
   2  * Copyright 2013 Paweł Dziepak, pdziepak@quarnos.org.
   3  * Distributed under the terms of the MIT License.
   4  */
   5 #ifndef _KERNEL_LOAD_TRACKING_H
   6 #define _KERNEL_LOAD_TRACKING_H
   7
   8
   9 #include <OS.h>
  10
  11
  12 const int32 kMaxLoad = 1000;
  13 const bigtime_t kLoadMeasureInterval = 1000;
  14 const bigtime_t kIntervalInaccuracy = kLoadMeasureInterval / 4;
  15
  16
  17 static inline int32
  18 compute_load(bigtime_t& measureTime, bigtime_t& measureActiveTime, int32& load,
  19         bigtime_t now)
  20 {
  21         if (measureTime == 0) {
  22                 measureTime = now;
  23                 return -1;
  24         }
  25
  26         bigtime_t deltaTime = now - measureTime;
  27
  28         if (deltaTime < kLoadMeasureInterval)
  29                 return -1;
  30
  31         int32 oldLoad = load;
  32         ASSERT(oldLoad >= 0 && oldLoad <= kMaxLoad);
  33
  34         int32 newLoad = measureActiveTime * kMaxLoad;
  35         newLoad /= max_c(deltaTime, 1);
  36         newLoad = max_c(min_c(newLoad, kMaxLoad), 0);
  37
  38         measureActiveTime = 0;
  39         measureTime = now;
  40
  41         deltaTime += kIntervalInaccuracy;
  42         int n = deltaTime / kLoadMeasureInterval;
  43         ASSERT(n > 0);
  44
  45         if (n > 10)
  46                 load = newLoad;
  47         else {
  48                 newLoad *= (1 << n) - 1;
  49                 load = (load + newLoad) / (1 << n);
  50                 ASSERT(load >= 0 && load <= kMaxLoad);
  51         }
  52
  53         return oldLoad;
  54 }
  55
  56
  57 #endif  // _KERNEL_LOAD_TRACKING_H