LXR qemu/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
  17typedef struct {
  18    int64_t next_slice_time;
  19    uint64_t slice_quota;
  20    uint64_t slice_ns;
  21    uint64_t dispatched;
  22} RateLimit;
  23
  24static 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
  41static 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
  49