netdev - Re: [PATCH 2/9] pasemi_mac: Clean TX ring in poll

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Message-ID: <4688F0CE.9020600@pobox.com>
Date:	Mon, 02 Jul 2007 08:34:22 -0400
From:	Jeff Garzik <jgarzik@...ox.com>
To:	Olof Johansson <olof@...om.net>
CC:	netdev@...r.kernel.org
Subject: Re: [PATCH 2/9] pasemi_mac: Clean TX ring in poll

Olof Johansson wrote:
> Clean the TX ring in the poll call, to avoid sitting on mapped buffers
> for a long time. NFS doesn't seem to like it much, for example.
> 
> 
> Signed-off-by: Olof Johansson <olof@...om.net>
> 
> Index: netdev-2.6/drivers/net/pasemi_mac.c
> ===================================================================
> --- netdev-2.6.orig/drivers/net/pasemi_mac.c
> +++ netdev-2.6/drivers/net/pasemi_mac.c
> @@ -1052,6 +1052,7 @@ static int pasemi_mac_poll(struct net_de
>  	int pkts, limit = min(*budget, dev->quota);
>  	struct pasemi_mac *mac = netdev_priv(dev);
>  
> +	pasemi_mac_clean_tx(mac);
>  	pkts = pasemi_mac_clean_rx(mac, limit);

Why is this needed?  Is your TX interrupt mitigated or delayed somehow?

In general, drivers should only clean TX in one place.  Doing so in 
multiple places tends to indicate a bug somewhere.

You are correct that you should not sit on buffers for too long -- that 
increases latency of all who are waiting on those buffers to be sent.


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