netdev - RE: [RFC net-next 2/2] net: fec: add ndo_select_queue to fix TX bandwidth fluctuations

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Date:   Tue, 25 May 2021 09:46:27 +0000
From:   Joakim Zhang <qiangqing.zhang@....com>
To:     Andrew Lunn <andrew@...n.ch>
CC:     "davem@...emloft.net" <davem@...emloft.net>,
        "kuba@...nel.org" <kuba@...nel.org>,
        "frieder.schrempf@...tron.de" <frieder.schrempf@...tron.de>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        dl-linux-imx <linux-imx@....com>
Subject: RE: [RFC net-next 2/2] net: fec: add ndo_select_queue to fix TX
 bandwidth fluctuations


Hi Andrew,

> -----Original Message-----
> From: Andrew Lunn <andrew@...n.ch>
> Sent: 2021年5月23日 22:46
> To: Joakim Zhang <qiangqing.zhang@....com>
> Cc: davem@...emloft.net; kuba@...nel.org; frieder.schrempf@...tron.de;
> netdev@...r.kernel.org; linux-kernel@...r.kernel.org; dl-linux-imx
> <linux-imx@....com>
> Subject: Re: [RFC net-next 2/2] net: fec: add ndo_select_queue to fix TX
> bandwidth fluctuations
> 
> On Sun, May 23, 2021 at 06:20:19PM +0800, Joakim Zhang wrote:
> > From: Fugang Duan <fugang.duan@....com>
> >
> > As we know that AVB is enabled by default, and the ENET IP design is
> > queue 0 for best effort, queue 1&2 for AVB Class A&B. Bandwidth of
> > queue 1&2 set in driver is 50%, TX bandwidth fluctuated when selecting
> > tx queues randomly with FEC_QUIRK_HAS_AVB quirk available.
> 
> How is the driver currently scheduling between these queues? Given the
> 802.1q priorities, i think we want queue 2 with the highest priority for
> scheduling. Then queue 0 and lastly queue 1.

I think currently there is no schedule between these queues in the driver.

Could you please point me where I can find mapping between priorities and queues? You prefer to below mapping?
static const u16 fec_enet_vlan_pri_to_queue[8] = {1, 1, 0, 0, 0, 2, 2, 2};

Best Regards,
Joakim Zhang
>     Andrew