On Fri, 2011-11-18 at 01:08 +0000, Ben Hutchings wrote:
> On Fri, 2011-11-11 at 18:34 +0530, Krishna Kumar wrote:
> > Changes for multiqueue virtio_net driver.
> [...]
> > @@ -677,25 +730,35 @@ static struct rtnl_link_stats64 *virtnet
> > {
> > struct virtnet_info *vi = netdev_priv(dev);
> > int cpu;
> > - unsigned int start;
> >
> > for_each_possible_cpu(cpu) {
> > - struct virtnet_stats __percpu *stats
> > - = per_cpu_ptr(vi->stats, cpu);
> > - u64 tpackets, tbytes, rpackets, rbytes;
> > -
> > - do {
> > - start = u64_stats_fetch_begin(&stats->syncp);
> > - tpackets = stats->tx_packets;
> > - tbytes = stats->tx_bytes;
> > - rpackets = stats->rx_packets;
> > - rbytes = stats->rx_bytes;
> > - } while (u64_stats_fetch_retry(&stats->syncp, start));
> > -
> > - tot->rx_packets += rpackets;
> > - tot->tx_packets += tpackets;
> > - tot->rx_bytes += rbytes;
> > - tot->tx_bytes += tbytes;
> > + int qpair;
> > +
> > + for (qpair = 0; qpair < vi->num_queue_pairs; qpair++) {
> > + struct virtnet_send_stats __percpu *tx_stat;
> > + struct virtnet_recv_stats __percpu *rx_stat;
>
> While you're at it, you can drop the per-CPU stats and make them only
> per-queue. There is unlikely to be any benefit in maintaining them
> per-CPU while receive and transmit processing is serialised per-queue.
It allows you to update stats without a lock.
Whats the benefit of having them per queue?
--
Sasha.
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