netdev - Re: [PATCH net-next v2 3/3] gianfar: Implement PAUSE frame generation support

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Message-Id: <20141029.143418.274385566081130545.davem@davemloft.net>
Date:	Wed, 29 Oct 2014 14:34:18 -0400 (EDT)
From:	David Miller <davem@...emloft.net>
To:	matei.pavaluca@...escale.com
Cc:	netdev@...r.kernel.org, claudiu.manoil@...escale.com
Subject: Re: [PATCH net-next v2 3/3] gianfar: Implement PAUSE frame
 generation support

From: Matei Pavaluca <matei.pavaluca@...escale.com>
Date: Mon, 27 Oct 2014 10:42:44 +0200

> The hardware can automatically generate pause frames when the number
> of free buffers drops under a certain threshold, but in order to do this,
> the address of the last free buffer needs to be written to a specific
> register for each RX queue.
> 
> This has to be done in 'gfar_clean_rx_ring' which is called for each
> RX queue. In order not to impact performance, by adding a register write
> for each incoming packet, this operation is done only when the PAUSE frame
> transmission is enabled.
> 
> Whenever the link is readjusted, this capability is turned on or off.
> 
> Signed-off-by: Matei Pavaluca <matei.pavaluca@...escale.com>

Applied.

But I would turn pause frames on by default, and deal with the
"performance" issue by aggregating the register writes.  Only
do it every N cleaned frames.
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