Date:	Tue, 4 Oct 2011 18:12:41 +0200
From:	Jiri Pirko <jpirko@...hat.com>
To:	Flavio Leitner <fbl@...hat.com>
Cc:	netdev@...r.kernel.org, davem@...emloft.net,
	eric.dumazet@...il.com, bhutchings@...arflare.com,
	shemminger@...tta.com, fubar@...ibm.com, andy@...yhouse.net,
	tgraf@...radead.org, ebiederm@...ssion.com, mirqus@...il.com,
	kaber@...sh.net, greearb@...delatech.com, jesse@...ira.com
Subject: Re: [patch net-next-2.6] net: introduce ethernet teaming device

Tue, Oct 04, 2011 at 04:53:44PM CEST, fbl@...hat.com wrote:

<snip>

>> +
>> +struct team_mode_ops {
>> +	int (*init)(struct team *team);
>> +	void (*exit)(struct team *team);
>> +	rx_handler_result_t (*receive)(struct team *team,
>> +				       struct team_port *port,
>> +				       struct sk_buff *skb);
>
>nitpick:
>As it doesn't have any other type of results, I would suggest
>to rename rx_handler_result_t be to shorter, i.e. rx_result_t.

Well that type is defined already in include/linux/netdevice.h
I like the original name better because it has "handler" word in it
(which imo reduces possible confusion)

>
>
>> +	bool (*transmit)(struct team *team, struct sk_buff *skb);
>> +	int (*port_enter)(struct team *team, struct team_port *port);
>
>Perhaps instead of 'port_enter', use 'port_join'.

Might be more appropriate, not sure (my eng skills recognize these two
as very similar in this case)

>
>
>> +	void (*port_leave)(struct team *team, struct team_port
>> *port);
>> +	void (*port_change_mac)(struct team *team, struct team_port
>> *port); +};
>> +
>> +enum team_option_type {
>> +	TEAM_OPTION_TYPE_U32,
>> +	TEAM_OPTION_TYPE_STRING,
>> +};
>> +
>> +struct team_option {
>> +	struct list_head list;
>> +	const char *name;
>> +	enum team_option_type type;
>> +	int (*getter)(struct team *team, void *arg);
>> +	int (*setter)(struct team *team, void *arg);
>
>What means getter and setter?

Option getter and setter. Function used to set and get the option.

>
>> +};
>> +
>> +struct team_mode {
>> +	const char *kind;
>> +	const struct team_mode_ops *ops;
>> +};
>> +
>> +struct rr_priv {
>> +	unsigned int sent_packets;
>> +};
>> +
>> +struct ab_priv {
>> +	struct team_port __rcu *active_port;
>> +};
>> +
>> +struct team {
>> +	struct net_device *dev; /* associated netdevice */
>> +	spinlock_t lock; /* used for overall locking, e.g. port
>> lists write */ +
>> +	/*
>> +	 * port lists with port count
>> +	 */
>> +	int port_count;
>> +	struct hlist_head *port_hlist;
>> +	struct list_head port_list;
>> +
>> +	struct list_head option_list;
>> +
>> +	const char *mode_kind;
>> +	struct team_mode_ops mode_ops;
>> +	union {
>> +		char priv_first_byte;
>> +		struct ab_priv ab_priv;
>> +		struct rr_priv rr_priv;
>> +	};
>
>I think the union should be a pointer or work in the same
>way as netdev_priv() does.

The reason I did this this way is saving one pointer dereference in hot
paths. In netdev priv the memory for priv data is allcated along with
netdev struct. In this case this is not possible because mode can be
changed during team device lifetime (and team priv is netdev priv).


<snip>

>> +
>> +static bool rr_transmit(struct team *team, struct sk_buff *skb)
>> +{
>> +	struct team_port *port;
>> +	int port_index;
>> +
>> +	port_index = team->rr_priv.sent_packets++ % team->port_count;
>> +	port = team_get_port_by_index_rcu(team, port_index);
>> +	port = __get_first_port_up(team, port);
>
>Well, __get_first_port_up() will frequently just do:
>
>	if (port->linkup)
>		return port;
>
>so, as it is in the hot TX path, can this be modified to be something
>like below to avoid one function call?
>
>        port = team_get_port_by_index_rcu(team, port_index);
>        if (unlikely(port->linkup))
>            port = __get_first_port_up(team, port);

Hmm, I don't think this is correct place to use "likely". Imagine you
have 2 ports and one of them is down all the team lifetime. You would
be hitting wrong branch always which will cause performance penalty.

>> +
>> +static const struct team_mode ab_mode = {
>> +	.kind		= "activebackup",
>> +	.ops		= &ab_mode_ops,
>> +};
>> +
>
>I would suggest to move each of the ab and rr specifics
>to their own module.  The idea is to have the team module
>as a generic module as possible and every mode on its module.
>Not sure what your plans are for this.

Well I was thinking about this for sure. One reason to have this in one
place is the mode_priv union you were referring to.
Other reason is that mode parts should be very easy and short. Also
their number should be limited (~4).


>
>
>> +/****************
>> + * Mode handling
>> + ****************/
>> +
>> +static const struct team_mode *team_modes[] = {
>> +	&rr_mode,
>> +	&ab_mode,
>> +};
>
>Following the above suggestion, this would require
>register/unregister ops.
>
>

<snip>

>> +
>> +static struct rtnl_link_stats64 *team_get_stats(struct net_device
>> *dev,
>> +						struct
>> rtnl_link_stats64 *stats) +{
>> +	struct team *team = netdev_priv(dev);
>> +	struct rtnl_link_stats64 temp;
>> +	struct team_port *port;
>> +
>> +	memset(stats, 0, sizeof(*stats));
>> +
>> +	rcu_read_lock();
>> +	list_for_each_entry_rcu(port, &team->port_list, list) {
>> +		const struct rtnl_link_stats64 *pstats;
>> +
>> +		pstats = dev_get_stats(port->dev, &temp);
>> +
>> +		stats->rx_packets += pstats->rx_packets;
>> +		stats->rx_bytes += pstats->rx_bytes;
>> +		stats->rx_errors += pstats->rx_errors;
>> +		stats->rx_dropped += pstats->rx_dropped;
>> +
>> +		stats->tx_packets += pstats->tx_packets;
>> +		stats->tx_bytes += pstats->tx_bytes;
>> +		stats->tx_errors += pstats->tx_errors;
>> +		stats->tx_dropped += pstats->tx_dropped;
>> +
>> +		stats->multicast += pstats->multicast;
>> +		stats->collisions += pstats->collisions;
>> +
>> +		stats->rx_length_errors += pstats->rx_length_errors;
>> +		stats->rx_over_errors += pstats->rx_over_errors;
>> +		stats->rx_crc_errors += pstats->rx_crc_errors;
>> +		stats->rx_frame_errors += pstats->rx_frame_errors;
>> +		stats->rx_fifo_errors += pstats->rx_fifo_errors;
>> +		stats->rx_missed_errors += pstats->rx_missed_errors;
>> +
>> +		stats->tx_aborted_errors +=
>> pstats->tx_aborted_errors;
>> +		stats->tx_carrier_errors +=
>> pstats->tx_carrier_errors;
>> +		stats->tx_fifo_errors += pstats->tx_fifo_errors;
>> +		stats->tx_heartbeat_errors +=
>> pstats->tx_heartbeat_errors;
>> +		stats->tx_window_errors += pstats->tx_window_errors;
>> +	}
>> +	rcu_read_unlock();
>> +
>> +	return stats;
>> +}
>
>I don't think computing stats like that is useful.  We can do
>that in userlevel with ethtool -S on each slave and sum all them.
>I think it would be better to have the errors computed based on
>events that happens inside of Team driver, so we can really see if
>something is happening inside of the Team driver or on its slaves.

I was thinking about this as well. I did this in same ways it's done in
bonding driver. One of reasons were that I can't count dropped packets
in team_handle_frame because I do not call netif_rx there and only
return RX_HANDLER_ANOTHER to "reinject" (saving one function call).

<snip>

>> +
>> +static int team_add_slave(struct net_device *dev, struct net_device
>> *port_dev) +{
>> +	struct team *team = netdev_priv(dev);
>> +	int err;
>> +
>> +	spin_lock(&team->lock);
>> +	err = team_port_add(team, port_dev);
>> +	spin_unlock(&team->lock);
>> +	return err;
>> +}
>
>I am not seeing any difference between slave and port, so why not stick
>with just one?

I like "port" better. It's more accurate. team_add/del_slave has its name
only because ndo is named the same.

<snip>

>
>fbl

Thanks for review Flavio.

Jirka
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