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From:   Kalle Valo <kvalo@codeaurora.org>
To:     Thomas Graf <post@thomas-graf.de>
Cc:     linux-wireless@vger.kernel.org, nbd@nbd.name
Subject: Re: [PATCH 5.10 2/3] mac80211: minstrel: remove deferred sampling code
References: <20201111183359.43528-1-nbd@nbd.name>
        <20201111183359.43528-2-nbd@nbd.name>
        <5a3c06de-0970-643f-e895-869dfb376fb9@thomas-graf.de>
Date:   Mon, 11 Oct 2021 13:52:36 +0300
In-Reply-To: <5a3c06de-0970-643f-e895-869dfb376fb9@thomas-graf.de> (Thomas
        Graf's message of "Wed, 28 Jul 2021 16:04:28 +0200")
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Thomas Graf <post@thomas-graf.de> writes:

> I tracked down an issue with using the Kernel 4.9.277 and 5.4.131 back
> to this patch.
>
> In 802.11bg mode the effective transmit rate drops to 3MBit/s.
> With that patch and perfect SNR (> 45dB) I get and rc_stats:
>
> *********************
> best   __________rate_________    ________statistics________
> ________last_______    ______sum-of________
> rate  [name idx airtime max_tp]  [avg(tp) avg(prob) sd(prob)]
> [prob.|retry|suc|att]  [#success | #attempts]
>         1     0    9738    0.9       0.9      93.7      0.5      75.0
> 1     3 4           562   572
>         2     1    4922    1.6       1.6      97.0      1.5     100.0
> 1     2 2           559   576
>         5.5   2    1858    4.7       4.7      99.9      0.0     100.0
> 2     2 2           542   565
>        11     3     982    9.1       9.1      94.9      1.2     100.0
> 4     3 3           560   578
>         6     4    1648    5.3       5.3      95.3      1.3     100.0
> 3     3 3           538   595
>         9     5    1112    8.0       8.0      97.5      1.8     100.0
> 4     2 2           560   596
>        12     6     844   10.5      10.5      92.4      2.0      75.0
> 5     3 4           572   615
>        18     7     576   15.5      15.4      89.0      1.4      66.6
> 5     2 3           559   609
>    D   24     8     440   20.4      20.4      99.4      1.1     100.0
> 6     2 2           560   604
>   C    36     9     308   29.1      29.1      98.7      1.6     100.0
> 6     2 2           565   600
>  B     48    10     240   37.3      36.3      87.3      1.4      66.6
> 6     2 3           608   671
> A   P  54    11     216   41.6      41.6      97.3      1.7     100.0
> 6     3 3           565   620
>
> Total packet count::    ideal 6111      lookaround 652
> *********************
>
> After reverting that patch the transmit rate is back to 20MBit/s:
> *********************
> best   __________rate_________    ________statistics________
> ________last_______    ______sum-of________
> rate  [name idx airtime max_tp]  [avg(tp) avg(prob) sd(prob)]
> [prob.|retry|suc|att]  [#success | #attempts]
>         1     0    9738    0.9       0.9      99.8      0.6     100.0
> 1     0 0            41   44
>         2     1    4922    1.6       1.6     100.0      0.0     100.0
> 1     0 0            45   45
>         5.5   2    1858    4.7       4.7      99.9      0.0     100.0
> 2     0 0            43   44
>        11     3     982    9.1       9.1      97.0      1.4     100.0
> 4     0 0            44   45
>         6     4    1648    5.3       5.3      99.9      0.0     100.0
> 3     0 0            43   44
>         9     5    1112    8.0       8.0      99.9      0.0     100.0
> 4     0 0            45   47
>        12     6     844   10.5       8.8      74.9      0.7       0.0
> 5     0 0            43   47
>        18     7     576   15.5      15.5     100.0      0.0     100.0
> 5     0 0            42   42
>    D   24     8     440   20.4      20.4      99.9      0.0     100.0
> 6     0 0            60   62
>   C P  36     9     308   29.1      29.1      99.9      0.0     100.0
> 6     0 0            44   46
> A      48    10     240   37.3      37.3      93.8      1.2     100.0
> 6     1 1           587   618
>  B     54    11     216   41.6      32.3      69.8      2.1      33.3
> 6     0 0         24506   25849
>
> Total packet count::    ideal 4962      lookaround 552
> *********************
>
> I'm using the ath9k driver with a sparklan WPEA-121N card.
>
> For my case reverting that patch is enough.
> What I see is that IEEE80211_TX_CTL_RATE_CTRL_PROBE is set but not
> used anywhere in the code. Maybe there is an easy and better fix than
> just reverting.

I lost track, is this regression resolved now or is it still open?

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