linux-kernel - RE: Re: [PATCH v2 1/2] net: ravb: Always process TX descriptor ring

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Date: Wed, 3 Apr 2024 09:28:00 +0000
From: Ratheesh Kannoth <rkannoth@...vell.com>
To: Paul Barker <paul.barker.ct@...renesas.com>,
        Jakub Kicinski
	<kuba@...nel.org>
CC: Sergey Shtylyov <s.shtylyov@....ru>,
        "David S. Miller"
	<davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>, Paolo Abeni
	<pabeni@...hat.com>,
        Niklas Söderlund
	<niklas.soderlund+renesas@...natech.se>,
        "netdev@...r.kernel.org"
	<netdev@...r.kernel.org>,
        "linux-renesas-soc@...r.kernel.org"
	<linux-renesas-soc@...r.kernel.org>,
        "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>
Subject: RE: Re: [PATCH v2 1/2] net: ravb: Always process TX descriptor ring

> From: Paul Barker <paul.barker.ct@...renesas.com>
> > AFAIU, TX is processed without any budget. This wont result in rx work
> > starvation if TX traffic is more ?
> 
> Quoting the docs in Documentation/networking/napi.rst:
> 
>     The method takes a ``budget`` argument - drivers can process
>     completions for any number of Tx packets but should only process up
>     to ``budget`` number of Rx packets.
> 
>     skb Tx processing should happen regardless of the ``budget``
> 
> I take that to mean that the RX work budget running out should not stop
> processing of TX packets.
> 
> Other drivers with a combined TX/RX poll function follow the same pattern of
> processing TX packets regardless of RX budget exhaustion, for example see
> ixgbe_poll() which processes TX packets first (in
> drivers/net/ethernet/intel/ixgbe/ixgbe_main.c).
ACK.  Thanks for pointing out. I had seen some drivers, TX NAPI routines exist to bring fairness to rx and tx. 
Just wondering, if there is a lot of tx traffic, would RX budget alone can do fairness among NAPI
Routines.