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35 lines
1.1 KiB
Diff
35 lines
1.1 KiB
Diff
From: Felix Fietkau <nbd@nbd.name>
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Date: Fri, 15 Jan 2021 12:15:06 +0100
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Subject: [PATCH] mac80211: minstrel_ht: fix rounding error in throughput
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calculation
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On lower data rates, the throughput calculation has a significant rounding
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error, causing rates like 48M and 54M OFDM to share the same throughput
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value with >= 90% success probablity.
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This is because the result of the division (prob_avg * 1000) / nsecs
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is really small (8 in this example).
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Improve accuracy by moving over some zeroes, making better use of the full
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range of u32 before the division.
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Signed-off-by: Felix Fietkau <nbd@nbd.name>
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---
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--- a/net/mac80211/rc80211_minstrel_ht.c
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+++ b/net/mac80211/rc80211_minstrel_ht.c
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@@ -445,10 +445,9 @@ minstrel_ht_get_tp_avg(struct minstrel_h
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* (prob is scaled - see MINSTREL_FRAC above)
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*/
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if (prob_avg > MINSTREL_FRAC(90, 100))
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- return MINSTREL_TRUNC(100000 * ((MINSTREL_FRAC(90, 100) * 1000)
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- / nsecs));
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- else
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- return MINSTREL_TRUNC(100000 * ((prob_avg * 1000) / nsecs));
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+ prob_avg = MINSTREL_FRAC(90, 100);
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+
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+ return MINSTREL_TRUNC(100 * ((prob_avg * 1000000) / nsecs));
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}
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/*
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