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Date: Mon, 9 Oct 2023 06:54:32 +0000 (UTC)
From: Kalle Valo <kvalo@...nel.org>
To: Jérôme Pouiller <jerome.pouiller@...abs.com>
Cc: linux-wireless@...r.kernel.org, linux-kernel@...r.kernel.org,
Felix Fietkau <nbd@....name>,
Felipe Negrelli Wolter <felipe.negrelliwolter@...abs.com>,
Olivier Souloumiac <olivier.souloumiac@...abs.com>,
Alexandr Suslenko <suslenko.o@...x.systems>,
Jérôme Pouiller
<jerome.pouiller@...abs.com>
Subject: Re: [PATCH v2] wifi: wfx: fix case where rates are out of order
Jérôme Pouiller <jerome.pouiller@...abs.com> wrote:
> From: Felipe Negrelli Wolter <felipe.negrelliwolter@...abs.com>
>
> When frames are sent over the air, the device always applies the data
> rates in descending order. The driver assumed Minstrel also provided
> rate in descending order.
>
> However, in some cases, Minstrel can a choose a fallback rate greater
> than the primary rate. In this case, the two rates was inverted, the
> device try highest rate first and we get many retries.
>
> Since the device always applies rates in descending order, the
> workaround is to drop the rate when it higher than its predecessor in
> the rate list. Thus [ 4, 5, 3 ] becomes [ 4, 3 ].
>
> This patch has been tested in isolated room with a series of
> attenuators. Here are the Minstrel statistics with 80dBm of attenuation:
>
> Without the fix:
>
> best ____________rate__________ ____statistics___ _____last____ ______sum-of________
> mode guard # rate [name idx airtime max_tp] [avg(tp) avg(prob)] [retry|suc|att] [#success | #attempts]
> HT20 LGI 1 S MCS0 0 1477 5.6 5.2 82.7 3 0 0 3 4
> HT20 LGI 1 MCS1 1 738 10.6 0.0 0.0 0 0 0 0 1
> HT20 LGI 1 D MCS2 2 492 14.9 13.5 81.5 5 0 0 5 9
> HT20 LGI 1 C MCS3 3 369 18.8 17.6 84.3 5 0 0 76 96
> HT20 LGI 1 A P MCS4 4 246 25.4 22.4 79.5 5 0 0 11268 14026
> HT20 LGI 1 B S MCS5 5 185 30.7 19.7 57.7 5 8 9 3918 9793
> HT20 LGI 1 MCS6 6 164 33.0 0.0 0.0 5 0 0 6 102
> HT20 LGI 1 MCS7 7 148 35.1 0.0 0.0 0 0 0 0 44
>
> With the fix:
>
> best ____________rate__________ ____statistics___ _____last____ ______sum-of________
> mode guard # rate [name idx airtime max_tp] [avg(tp) avg(prob)] [retry|suc|att] [#success | #attempts]
> HT20 LGI 1 S MCS0 0 1477 5.6 1.8 28.6 1 0 0 1 5
> HT20 LGI 1 DP MCS1 1 738 10.6 9.7 82.6 4 0 0 14 34
> HT20 LGI 1 MCS2 2 492 14.9 9.2 55.4 5 0 0 52 77
> HT20 LGI 1 B S MCS3 3 369 18.8 15.6 74.9 5 1 1 417 554
> HT20 LGI 1 A MCS4 4 246 25.4 16.7 59.2 5 1 1 13812 17951
> HT20 LGI 1 C S MCS5 5 185 30.7 14.0 41.0 5 1 5 57 640
> HT20 LGI 1 MCS6 6 164 33.0 0.0 0.0 0 0 1 0 48
> HT20 LGI 1 S MCS7 7 148 35.1 0.0 0.0 0 0 0 0 36
>
> We can notice the device try now to send with lower rates (and high
> success rates). At the end, we measured 20-25% better throughput with
> this patch.
>
> Fixes: 9bca45f3d692 ("staging: wfx: allow to send 802.11 frames")
> Tested-by: Olivier Souloumiac <olivier.souloumiac@...abs.com>
> Tested-by: Alexandr Suslenko <suslenko.o@...x.systems>
> Reported-by: Alexandr Suslenko <suslenko.o@...x.systems>
> Co-developed-by: Jérôme Pouiller <jerome.pouiller@...abs.com>
> Signed-off-by: Jérôme Pouiller <jerome.pouiller@...abs.com>
> Signed-off-by: Felipe Negrelli Wolter <felipe.negrelliwolter@...abs.com>
Patch applied to wireless-next.git, thanks.
ea2274ab0b18 wifi: wfx: fix case where rates are out of order
--
https://patchwork.kernel.org/project/linux-wireless/patch/20231004123039.157112-1-jerome.pouiller@silabs.com/
https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches
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