netdev - Re: [PATCH net 6/7] net: axienet: fix for TX busy handling

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Message-ID: <20220111194948.056c7211@kicinski-fedora-PC1C0HJN.hsd1.ca.comcast.net>
Date:   Tue, 11 Jan 2022 19:49:48 -0800
From:   Jakub Kicinski <kuba@...nel.org>
To:     Robert Hancock <robert.hancock@...ian.com>
Cc:     netdev@...r.kernel.org, radhey.shyam.pandey@...inx.com,
        davem@...emloft.net
Subject: Re: [PATCH net 6/7] net: axienet: fix for TX busy handling

On Tue, 11 Jan 2022 15:13:57 -0600 Robert Hancock wrote:
> We should be avoiding returning NETDEV_TX_BUSY from ndo_start_xmit in
> normal cases. Move the main check for a full TX ring to the end of the
> function so that we stop the queue after the last available space is used
> up, and only wake up the queue if enough space is available for a full
> maximally fragmented packet. Print a warning if there is insufficient
> space at the start of start_xmit, since this should no longer happen.
> 
> Fixes: 8a3b7a252dca9 ("drivers/net/ethernet/xilinx: added Xilinx AXI Ethernet driver")
> Signed-off-by: Robert Hancock <robert.hancock@...ian.com>

Feels a little more like an optimization than strictly a fix.
Can we apply this and the following patch to net-next in two
week's time? It's not too much of a stretch to take it in now
if it's a bit convenience but I don't think the Fixes tags should 
stay.

> -		netif_wake_queue(ndev);
> +		netdev_warn(ndev, "TX ring unexpectedly full\n");

Probably wise to make this netdev_warn_once() or at least rate limit it.

> +		return NETDEV_TX_BUSY;
>  	}
>  
>  	if (skb->ip_summed == CHECKSUM_PARTIAL) {