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

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Message-ID: <20170203155822.GD3653@Red>
Date:   Fri, 3 Feb 2017 16:58:22 +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 Fri, Feb 03, 2017 at 10:15:30AM -0500, David Miller wrote:
> From: Corentin Labbe <clabbe.montjoie@...il.com>
> Date: Fri, 3 Feb 2017 14:41:45 +0100
> 
> > 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)
> 
> We have no control over nor care about what the Linux Foundation writes
> about the Linux networking code.
> 
> Complain to them and please do not bother us about it.
> 
> Thank you.

Sorry, this was not to bother you.

Could you give me your opinion on the other question of the mail ? (just copied below)
So perhaps the best way is to do like intel igb/ixgbe, keeping under NAPI until the stmmac_tx_clean function said that it finished handling the queue (with a distinct TX budget)?

Thanks
Regards