From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001 From: Wolfgang Bumiller Date: Tue, 6 Feb 2018 11:34:34 +0100 Subject: [PATCH] ratelimit: don't align wait time with slices It is possible for rate limited writes to keep overshooting a slice's quota by a tiny amount causing the slice-aligned waiting period to effectively halve the rate. Signed-off-by: Wolfgang Bumiller --- include/qemu/ratelimit.h | 11 +++++------ 1 file changed, 5 insertions(+), 6 deletions(-) diff --git a/include/qemu/ratelimit.h b/include/qemu/ratelimit.h index 8dece483f5..1b38291823 100644 --- a/include/qemu/ratelimit.h +++ b/include/qemu/ratelimit.h @@ -36,7 +36,7 @@ typedef struct { static inline int64_t ratelimit_calculate_delay(RateLimit *limit, uint64_t n) { int64_t now = qemu_clock_get_ns(QEMU_CLOCK_REALTIME); - uint64_t delay_slices; + double delay_slices; assert(limit->slice_quota && limit->slice_ns); @@ -55,12 +55,11 @@ static inline int64_t ratelimit_calculate_delay(RateLimit *limit, uint64_t n) return 0; } - /* Quota exceeded. Calculate the next time slice we may start - * sending data again. */ - delay_slices = (limit->dispatched + limit->slice_quota - 1) / - limit->slice_quota; + /* Quota exceeded. Wait based on the excess amount and then start a new + * slice. */ + delay_slices = (double)limit->dispatched / limit->slice_quota; limit->slice_end_time = limit->slice_start_time + - delay_slices * limit->slice_ns; + (uint64_t)(delay_slices * limit->slice_ns); return limit->slice_end_time - now; } -- 2.11.0