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
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.
10 Signed-off-by: Wolfgang Bumiller <w.bumiller@proxmox.com>
12 include/qemu/ratelimit.h | 11 +++++------
13 1 file changed, 5 insertions(+), 6 deletions(-)
15 diff --git a/include/qemu/ratelimit.h b/include/qemu/ratelimit.h
16 index 8dece483f5..1b38291823 100644
17 --- a/include/qemu/ratelimit.h
18 +++ b/include/qemu/ratelimit.h
19 @@ -36,7 +36,7 @@ typedef struct {
20 static inline int64_t ratelimit_calculate_delay(RateLimit *limit, uint64_t n)
22 int64_t now = qemu_clock_get_ns(QEMU_CLOCK_REALTIME);
23 - uint64_t delay_slices;
24 + double delay_slices;
26 assert(limit->slice_quota && limit->slice_ns);
28 @@ -55,12 +55,11 @@ static inline int64_t ratelimit_calculate_delay(RateLimit *limit, uint64_t n)
32 - /* Quota exceeded. Calculate the next time slice we may start
33 - * sending data again. */
34 - delay_slices = (limit->dispatched + limit->slice_quota - 1) /
36 + /* Quota exceeded. Wait based on the excess amount and then start a new
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;