netdev - Re: [PATCH 4/5 v2] ifb: add multiqueue support

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Date:	Tue, 14 Dec 2010 16:59:18 +0100
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Changli Gao <xiaosuo@...il.com>
Cc:	Jamal Hadi Salim <hadi@...erus.ca>,
	"David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org
Subject: Re: [PATCH 4/5 v2] ifb: add multiqueue support

Le mardi 14 décembre 2010 à 23:21 +0800, Changli Gao a écrit :


> +static struct rtnl_link_stats64 *ifb_get_stats64(struct net_device *dev,
> +		struct rtnl_link_stats64 *stats)
> +{
> +	struct ifb_q_private *q;
> +	struct netdev_queue *txq;
> +	int cpu;
> +	u64 rx_packets, rx_bytes, rx_dropped;
> +	u64 tx_packets, tx_bytes, tx_dropped;
> +	unsigned int start;
> +
> +	for_each_possible_cpu(cpu) {
> +		q = per_cpu_ptr(ifb_priv(dev), cpu);
> +		txq = q->txq;
> +		do {
> +			start = u64_stats_fetch_begin_bh(&q->syncp);
> +			rx_packets = q->rx_packets;
> +			rx_bytes = q->rx_bytes;
> +			rx_dropped = q->rx_dropped;
> +			tx_packets = txq->tx_packets;
> +			tx_bytes = txq->tx_bytes;
> +			tx_dropped = txq->tx_dropped;
> +		} while (u64_stats_fetch_retry_bh(&q->syncp, start));
> +		stats->rx_packets += rx_packets;
> +		stats->rx_bytes += rx_bytes;
> +		stats->rx_dropped += rx_dropped;
> +		stats->tx_packets += tx_packets;
> +		stats->tx_bytes += tx_bytes;
> +		stats->tx_dropped += tx_dropped;
> +	}
> +
> +	return stats;
> +}
> +


There is a problem here.

You should sum in the loop rx_counters only, (the counters syncp
protected), and use dev_txq_stats_fold() to get the tx_counters from
core network.

dev_txq_stats_fold(dev, stats);
for_each_possible_cpu(cpu) {
	q = per_cpu_ptr(ifb_priv(dev), cpu);
	txq = q->txq;
	do {
		start = u64_stats_fetch_begin_bh(&q->syncp);
		rx_packets = q->rx_packets;
		rx_bytes   = q->rx_bytes;
		rx_dropped = q->rx_dropped;
	} while (u64_stats_fetch_retry_bh(&q->syncp, start));
	stats->rx_packets += rx_packets;
	stats->rx_bytes   += rx_bytes;
	stats->rx_dropped += rx_dropped;
}
return stats;


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