linux-kernel - Re: [PATCH 13/17] net: stmmac: Implement NAPI for TX

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Message-ID: <20170203134145.GB3653@Red>
Date:   Fri, 3 Feb 2017 14:41:45 +0100
From:   Corentin Labbe <clabbe.montjoie@...il.com>
To:     David Miller <davem@...emloft.net>
Cc:     peppe.cavallaro@...com, alexandre.torgue@...com,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 13/17] net: stmmac: Implement NAPI for TX

On Tue, Jan 31, 2017 at 11:12:25PM -0500, David Miller wrote:
> From: Corentin Labbe <clabbe.montjoie@...il.com>
> Date: Tue, 31 Jan 2017 10:11:48 +0100
> 
> > The stmmac driver run TX completion under NAPI but without checking
> > the work done by the TX completion function.
> 
> The current behavior is correct and completely intentional.
> 
> A driver should _never_ account TX work to the NAPI poll budget.
> 
> This is because TX liberation is orders of magnitude cheaper than
> receiving a packet, and such SKB freeing makes more SKBs available
> for RX processing.
> 
> Therefore, TX work should never count against the NAPI budget.
> 
> Please do not fix something which is not broken.

So at least the documentation I read must be fixed (https://wiki.linuxfoundation.org/networking/napi)

So perhaps the best way is to do like intel igb/ixgbe, keeping under NAPI until the stmmac_tx_clean function said that it finish handling the queue ?

Regards
Corentin Labbe