From 90b3984e6026b28f90a820c461e11812d5d4e930 Mon Sep 17 00:00:00 2001 From: Felix Fietkau <nbd@openwrt.org> Date: Sat, 14 Mar 2015 02:00:44 +0000 Subject: [PATCH] mac80211: fix a rounding issue in minstrel MCS rate duration calculation Signed-off-by: Felix Fietkau <nbd@openwrt.org> SVN-Revision: 44749 --- ...l_ht-fix-rounding-issue-in-MCS-durat.patch | 43 +++++++++++++++++++ 1 file changed, 43 insertions(+) create mode 100644 package/kernel/mac80211/patches/308-mac80211-minstrel_ht-fix-rounding-issue-in-MCS-durat.patch diff --git a/package/kernel/mac80211/patches/308-mac80211-minstrel_ht-fix-rounding-issue-in-MCS-durat.patch b/package/kernel/mac80211/patches/308-mac80211-minstrel_ht-fix-rounding-issue-in-MCS-durat.patch new file mode 100644 index 0000000000..d13263655e --- /dev/null +++ b/package/kernel/mac80211/patches/308-mac80211-minstrel_ht-fix-rounding-issue-in-MCS-durat.patch @@ -0,0 +1,43 @@ +From: Felix Fietkau <nbd@openwrt.org> +Date: Fri, 13 Mar 2015 10:49:40 +0100 +Subject: [PATCH] mac80211: minstrel_ht: fix rounding issue in MCS duration + calculation + +On very high MCS bitrates, the calculated duration of rates that are +next to each other can be very imprecise, due to the small packet size +used as reference (1200 bytes). +This is most visible in VHT80 nss=2 MCS8/9, for which minstrel shows the +same throughput when the probability is also the same. This leads to a +bad rate selection for such rates. + +Fix this issue by introducing an average A-MPDU size factor into the +calculation. + +Signed-off-by: Felix Fietkau <nbd@openwrt.org> +--- + +--- a/net/mac80211/rc80211_minstrel_ht.c ++++ b/net/mac80211/rc80211_minstrel_ht.c +@@ -17,10 +17,11 @@ + #include "rc80211_minstrel.h" + #include "rc80211_minstrel_ht.h" + ++#define AVG_AMPDU_SIZE 16 + #define AVG_PKT_SIZE 1200 + + /* Number of bits for an average sized packet */ +-#define MCS_NBITS (AVG_PKT_SIZE << 3) ++#define MCS_NBITS ((AVG_PKT_SIZE * AVG_AMPDU_SIZE) << 3) + + /* Number of symbols for a packet with (bps) bits per symbol */ + #define MCS_NSYMS(bps) DIV_ROUND_UP(MCS_NBITS, (bps)) +@@ -33,7 +34,8 @@ + ) + + /* Transmit duration for the raw data part of an average sized packet */ +-#define MCS_DURATION(streams, sgi, bps) MCS_SYMBOL_TIME(sgi, MCS_NSYMS((streams) * (bps))) ++#define MCS_DURATION(streams, sgi, bps) \ ++ (MCS_SYMBOL_TIME(sgi, MCS_NSYMS((streams) * (bps))) / AVG_AMPDU_SIZE) + + #define BW_20 0 + #define BW_40 1 -- GitLab