include/qemu/ratelimit.h

   1 /*
   2  * Ratelimiting calculations
   3  *
   4  * Copyright IBM, Corp. 2011
   5  *
   6  * Authors:
   7  *  Stefan Hajnoczi   <stefanha@linux.vnet.ibm.com>
   8  *
   9  * This work is licensed under the terms of the GNU LGPL, version 2 or later.
  10  * See the COPYING.LIB file in the top-level directory.
  11  *
  12  */
  13
  14 #ifndef QEMU_RATELIMIT_H
  15 #define QEMU_RATELIMIT_H 1
  16
  17 typedef struct {
  18     int64_t next_slice_time;
  19     uint64_t slice_quota;
  20     uint64_t slice_ns;
  21     uint64_t dispatched;
  22 } RateLimit;
  23
  24 static inline int64_t ratelimit_calculate_delay(RateLimit *limit, uint64_t n)
  25 {
  26     int64_t now = qemu_clock_get_ns(QEMU_CLOCK_REALTIME);
  27
  28     if (limit->next_slice_time < now) {
  29         limit->next_slice_time = now + limit->slice_ns;
  30         limit->dispatched = 0;
  31     }
  32     if (limit->dispatched == 0 || limit->dispatched + n <= limit->slice_quota) {
  33         limit->dispatched += n;
  34         return 0;
  35     } else {
  36         limit->dispatched = n;
  37         return limit->next_slice_time - now;
  38     }
  39 }
  40
  41 static inline void ratelimit_set_speed(RateLimit *limit, uint64_t speed,
  42                                        uint64_t slice_ns)
  43 {
  44     limit->slice_ns = slice_ns;
  45     limit->slice_quota = ((double)speed * slice_ns)/1000000000ULL;
  46 }
  47
  48 #endif