netdev - RE: [PATCH v2 net-next 0/7] dpaa2-eth: add support for Rx traffic classes

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Message-ID: <VI1PR0402MB3871F0358FE1369A2F00621DE0BD0@VI1PR0402MB3871.eurprd04.prod.outlook.com>
Date:   Fri, 15 May 2020 20:48:27 +0000
From:   Ioana Ciornei <ioana.ciornei@....com>
To:     Jakub Kicinski <kuba@...nel.org>
CC:     "davem@...emloft.net" <davem@...emloft.net>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: RE: [PATCH v2 net-next 0/7] dpaa2-eth: add support for Rx traffic
 classes


> Subject: Re: [PATCH v2 net-next 0/7] dpaa2-eth: add support for Rx traffic
> classes
> 
> On Fri, 15 May 2020 19:31:18 +0000 Ioana Ciornei wrote:
> > > Subject: Re: [PATCH v2 net-next 0/7] dpaa2-eth: add support for Rx
> > > traffic classes
> > >
> > > On Fri, 15 May 2020 21:47:46 +0300 Ioana Ciornei wrote:
> > > > This patch set adds support for Rx traffic classes on DPAA2
> > > > Ethernet devices.
> > > >
> > > > The first two patches make the necessary changes so that multiple
> > > > traffic classes are configured and their statistics are displayed
> > > > in the debugfs. The third patch adds a static distribution to said
> > > > traffic classes based on the VLAN PCP field.
> > > >
> > > > The last patches add support for the congestion group taildrop
> > > > mechanism that allows us to control the number of frames that can
> > > > accumulate on a group of Rx frame queues belonging to the same traffic
> class.
> > >
> > > Ah, I miseed you already sent a v2. Same question applies:
> > >
> > > > How is this configured from the user perspective? I looked through
> > > > the patches and I see no information on how the input is taken
> > > > from the user.
> >
> > There is no input taken from the user at the moment. The traffic class
> > id is statically selected based on the VLAN PCP field. The
> > configuration for this is added in patch 3/7.
> 
> Having some defaults for RX queue per TC is understandable. But patch 1
> changes how many RX queues are used in the first place. Why if user does not
> need RX queues per TC?

In DPAA2 we have a boot time configurable system in which the user can select
for each interface how many queues and how many traffic classes it needs.

The driver picks these up from firmware and configures the traffic class
distribution only if there is more than one requested.
With one TC the behavior of the driver is exactly as before.

Ioana