debian/patches/extra/0035-ratelimit-don-t-align-wait-time-with-slices.patch

   1 From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
   2 From: Wolfgang Bumiller <w.bumiller@proxmox.com>
   3 Date: Tue, 6 Feb 2018 11:34:34 +0100
   4 Subject: [PATCH] ratelimit: don't align wait time with slices
   5
   6 It is possible for rate limited writes to keep overshooting a slice's
   7 quota by a tiny amount causing the slice-aligned waiting period to
   8 effectively halve the rate.
   9
  10 Signed-off-by: Wolfgang Bumiller <w.bumiller@proxmox.com>
  11 ---
  12  include/qemu/ratelimit.h | 11 +++++------
  13  1 file changed, 5 insertions(+), 6 deletions(-)
  14
  15 diff --git a/include/qemu/ratelimit.h b/include/qemu/ratelimit.h
  16 index 8da1232574..324ff04fe2 100644
  17 --- a/include/qemu/ratelimit.h
  18 +++ b/include/qemu/ratelimit.h
  19 @@ -35,7 +35,7 @@ typedef struct {
  20  static inline int64_t ratelimit_calculate_delay(RateLimit *limit, uint64_t n)
  21  {
  22      int64_t now = qemu_clock_get_ns(QEMU_CLOCK_REALTIME);
  23 -    uint64_t delay_slices;
  24 +    double delay_slices;
  25
  26      assert(limit->slice_quota && limit->slice_ns);
  27
  28 @@ -54,12 +54,11 @@ static inline int64_t ratelimit_calculate_delay(RateLimit *limit, uint64_t n)
  29          return 0;
  30      }
  31
  32 -    /* Quota exceeded. Calculate the next time slice we may start
  33 -     * sending data again. */
  34 -    delay_slices = (limit->dispatched + limit->slice_quota - 1) /
  35 -        limit->slice_quota;
  36 +    /* Quota exceeded. Wait based on the excess amount and then start a new
  37 +     * slice. */
  38 +    delay_slices = (double)limit->dispatched / limit->slice_quota;
  39      limit->slice_end_time = limit->slice_start_time +
  40 -        delay_slices * limit->slice_ns;
  41 +        (uint64_t)(delay_slices * limit->slice_ns);
  42      return limit->slice_end_time - now;
  43  }
  44
  45 --
  46 2.11.0
  47