On Wed, 2012-06-06 at 15:52 +0800, Jason Wang wrote:
> Currently, we store the statistics in the independent fields of virtnet_stats,
> this is not scalable when we want to add more counters. As suggested by Michael,
> this patch convert it to an array and use the enum as the index to access them.
>
> Signed-off-by: Jason Wang <jasowang@xxxxxxxxxx>
> ---
> drivers/net/virtio_net.c | 30 +++++++++++++++++-------------
> 1 files changed, 17 insertions(+), 13 deletions(-)
>
> struct virtnet_stats {
> struct u64_stats_sync syncp;
> - u64 tx_bytes;
> - u64 tx_packets;
> -
> - u64 rx_bytes;
> - u64 rx_packets;
> + u64 data[VIRTNET_NUM_STATS];
> };
>
Interesting, but I fear you'll have a lot of problems.
Current code is buggy, and you are adding more possible races.
We could have one cpu doing the :
u64_stats_update_begin(&stats->syncp);
stats->rx_bytes += skb->len;
stats->rx_packets++;
u64_stats_update_end(&stats->syncp);
And another one doing :
u64_stats_update_begin(&stats->syncp);
stats->tx_bytes += skb->len;
stats->tx_packets++;
u64_stats_update_end(&stats->syncp);
And one syncp sequence increment can be lost, since both cpus are
basically doing this at the same time :
write_seqcount_begin(&syncp->seq);
I'll send a fix in a separate thread.
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