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