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

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Message-ID: <20200520121252.6cee8674@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
Date:   Wed, 20 May 2020 12:12:52 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     Ioana Ciornei <ioana.ciornei@....com>
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

On Wed, 20 May 2020 15:10:42 +0000 Ioana Ciornei wrote:
> DPAA2 has frame queues per each Rx traffic class and the decision from which queue
> to pull frames from is made by the HW based on the queue priority within a channel
> (there is one channel per each CPU).

IOW you're reading the descriptor for the device memory/iomem address
and the HW will return the next descriptor based on configured priority?
Presumably strict priority?

> If this should be modeled in software, then I assume there should be a NAPI instance
> for each traffic class and the stack should know in which order to call the poll()
> callbacks so that the priority is respected.

Right, something like that. But IMHO not needed if HW can serve the
right descriptor upon poll.