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From:   Kalle Valo <kvalo@kernel.org>
To:     petter@technux.se
Cc:     linux-wireless@vger.kernel.org, s.hauer@pengutronix.de,
        Larry.Finger@lwfinger.net, andreas@fatal.se, g0000ga@gmail.com,
        iam@valdikss.org.ru, kernel@pengutronix.de, linux@ulli-kroll.de,
        morrownr@gmail.com, mr.nuke.me@gmail.com, pkshih@realtek.com,
        tpkuester@gmail.com, Petter Mabacker <petter.mabacker@esab.se>
Subject: Re: [PATCH] wifi: rtw88: usb: Make work queues high prio
References: <20230530091532.2711675-1-petter@technux.se>
Date:   Tue, 30 May 2023 13:25:39 +0300
In-Reply-To: <20230530091532.2711675-1-petter@technux.se> (petter's message of
        "Tue, 30 May 2023 11:15:32 +0200")
Message-ID: <87zg5mjeu4.fsf@kernel.org>
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petter@technux.se writes:

> From: Petter Mabacker <petter.mabacker@esab.se>
>
> The rtw8822cu driver have problem to handle high rx or tx rates compared
> with high load (such as high I/O) on slower systems, such as for example
> i.MX6 SoloX and similar platforms.
>
> The problems are more frequent when having the access point close to the
> device. On slower systems it's often enough to download a large file,
> combined with generating I/O load to trigger:
>
> [  374.763424] rtw_8822cu 1-1.2:1.2: failed to get tx report from firmware
> [  377.771790] rtw_8822cu 1-1.2:1.2: failed to send h2c command
> [  407.813460] rtw_8822cu 1-1.2:1.2: firmware failed to report density after scan
> [  414.965826] rtw_8822cu 1-1.2:1.2: failed to send h2c command
> [  444.993462] rtw_8822cu 1-1.2:1.2: firmware failed to report density after scan
> [  452.144551] rtw_8822cu 1-1.2:1.2: failed to send h2c command
> [  482.183445] rtw_8822cu 1-1.2:1.2: firmware failed to report density after scan
> [  489.426263] rtw_8822cu 1-1.2:1.2: failed to send h2c command
>
> Another way is to simply perform a wifi rescan.
>
> Benchmarking shows that setting a high prio workqueue for tx/rx will
> significally improve things. Also compared alloc_workqueue with
> alloc_ordered_workqueue, but even thou the later seems to slightly
> improve things it's still quite easy to reproduce the above issues. So
> that leads to the decision to go for alloc_workqueue.
>
> Thanks to Ping-Ke Shih <pkshih@realtek.com> that came up with the idea
> of exploring tweaking of the work queue's within a similar discussion.
>
> Fixes: a82dfd33d1237 ("wifi: rtw88: Add common USB chip support")
> Signed-off-by: Petter Mabacker <petter.mabacker@esab.se>
> ---
>  drivers/net/wireless/realtek/rtw88/usb.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/net/wireless/realtek/rtw88/usb.c b/drivers/net/wireless/realtek/rtw88/usb.c
> index 44a5fafb9905..bfe0845528ec 100644
> --- a/drivers/net/wireless/realtek/rtw88/usb.c
> +++ b/drivers/net/wireless/realtek/rtw88/usb.c
> @@ -716,7 +716,7 @@ static int rtw_usb_init_rx(struct rtw_dev *rtwdev)
>  	struct rtw_usb *rtwusb = rtw_get_usb_priv(rtwdev);
>  	int i;
>  
> -	rtwusb->rxwq = create_singlethread_workqueue("rtw88_usb: rx wq");
> +	rtwusb->rxwq = alloc_workqueue("rtw88_usb: rx wq", WQ_UNBOUND | WQ_HIGHPRI, 0);
>  	if (!rtwusb->rxwq) {
>  		rtw_err(rtwdev, "failed to create RX work queue\n");
>  		return -ENOMEM;
> @@ -750,7 +750,7 @@ static int rtw_usb_init_tx(struct rtw_dev *rtwdev)
>  	struct rtw_usb *rtwusb = rtw_get_usb_priv(rtwdev);
>  	int i;
>  
> -	rtwusb->txwq = create_singlethread_workqueue("rtw88_usb: tx wq");
> +	rtwusb->txwq = alloc_workqueue("rtw88_usb: tx wq", WQ_UNBOUND | WQ_HIGHPRI, 0);
>  	if (!rtwusb->txwq) {
>  		rtw_err(rtwdev, "failed to create TX work queue\n");
>  		return -ENOMEM;

Should this workqueue be ordered or not? Please check Tejun's patchset
about using ordered queues:

https://lore.kernel.org/lkml/20230421025046.4008499-1-tj@kernel.org/

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