netdev - Re: [PATCH 3/4] ethtool: can't set combined and tx/rx channel counts at the same time

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Message-ID: <20160208205247.74aaaee8@jkicinski-Precision-T1700>
Date:	Mon, 8 Feb 2016 20:52:47 +0000
From:	Jakub Kicinski <moorray3@...pl>
To:	Jacob Keller <jacob.e.keller@...el.com>
Cc:	netdev@...r.kernel.org, davem@...emloft.net
Subject: Re: [PATCH 3/4] ethtool: can't set combined and tx/rx channel
 counts at the same time

On Mon,  8 Feb 2016 12:06:04 -0800, Jacob Keller wrote:
> +	/* can't set combined and separate channels at the same time */
> +	if ((channels.combined_count &&
> +	     (channels.rx_count || channels.tx_count))
> +	    return -EINVAL;
> +
>  	/* ensure the new Rx count fits within the configured Rx flow
>  	 * indirection table settings */
>  	if (netif_is_rxfh_configured(dev) &&

My understanding is that unsymmetrical rx/tx queue configuration with
combined IRQ vectors should be expressed as:

combined = min(tx, rx);
num_tx = tx - combined;
num_rx = rx - combined;

Please see:

https://www.mail-archive.com/netdev@vger.kernel.org/msg93977.html

Patches which I cooked up for this are rotting in my queue blocked by
other things, unfortunately.