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Date: Thu, 14 May 2015 00:52:26 -0400 (EDT)
From: David Miller <davem@...emloft.net>
To: sixiao@...rosoft.com
Cc: kys@...rosoft.com, haiyangz@...rosoft.com,
devel@...uxdriverproject.org, netdev@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next,1/1] hv_netvsc: use per_cpu stats to calculate
TX/RX data
From: sixiao@...rosoft.com
Date: Tue, 12 May 2015 15:50:02 -0700
> From: Simon Xiao <sixiao@...rosoft.com>
>
> Current code does not lock anything when calculating the TX and RX stats.
> As a result, the RX and TX data reported by ifconfig are not accuracy in a
> system with high network throughput and multiple CPUs (in my test,
> RX/TX = 83% between 2 HyperV VM nodes which have 8 vCPUs and 40G Ethernet).
>
> This patch fixed the above issue by using per_cpu stats.
> netvsc_get_stats64() summarizes TX and RX data by iterating over all CPUs
> to get their respective stats.
>
> Signed-off-by: Simon Xiao <sixiao@...rosoft.com>
> Reviewed-by: K. Y. Srinivasan <kys@...rosoft.com>
> Reviewed-by: Haiyang Zhang <haiyangz@...rosoft.com>
> ---
> drivers/net/hyperv/hyperv_net.h | 9 +++++
> drivers/net/hyperv/netvsc_drv.c | 80 ++++++++++++++++++++++++++++++++++++-----
> 2 files changed, 81 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/net/hyperv/hyperv_net.h b/drivers/net/hyperv/hyperv_net.h
> index 41071d3..5a92b36 100644
> --- a/drivers/net/hyperv/hyperv_net.h
> +++ b/drivers/net/hyperv/hyperv_net.h
> @@ -611,6 +611,12 @@ struct multi_send_data {
> u32 count; /* counter of batched packets */
> };
>
> +struct netvsc_stats {
> + u64 packets;
> + u64 bytes;
> + struct u64_stats_sync s_sync;
> +};
> +
> /* The context of the netvsc device */
> struct net_device_context {
> /* point back to our device context */
> @@ -618,6 +624,9 @@ struct net_device_context {
> struct delayed_work dwork;
> struct work_struct work;
> u32 msg_enable; /* debug level */
> +
> + struct netvsc_stats __percpu *tx_stats;
> + struct netvsc_stats __percpu *rx_stats;
> };
>
> /* Per netvsc device */
> diff --git a/drivers/net/hyperv/netvsc_drv.c b/drivers/net/hyperv/netvsc_drv.c
> index 5993c7e..310b902 100644
> --- a/drivers/net/hyperv/netvsc_drv.c
> +++ b/drivers/net/hyperv/netvsc_drv.c
> @@ -391,7 +391,7 @@ static int netvsc_start_xmit(struct sk_buff *skb, struct net_device *net)
> u32 skb_length;
> u32 pkt_sz;
> struct hv_page_buffer page_buf[MAX_PAGE_BUFFER_COUNT];
> -
> + struct netvsc_stats *tx_stats = this_cpu_ptr(net_device_ctx->tx_stats);
>
> /* We will atmost need two pages to describe the rndis
> * header. We can only transmit MAX_PAGE_BUFFER_COUNT number
> @@ -580,8 +580,10 @@ do_send:
>
> drop:
> if (ret == 0) {
> - net->stats.tx_bytes += skb_length;
> - net->stats.tx_packets++;
> + u64_stats_update_begin(&tx_stats->s_sync);
> + tx_stats->packets++;
> + tx_stats->bytes += skb_length;
> + u64_stats_update_end(&tx_stats->s_sync);
> } else {
> if (ret != -EAGAIN) {
> dev_kfree_skb_any(skb);
> @@ -644,13 +646,17 @@ int netvsc_recv_callback(struct hv_device *device_obj,
> struct ndis_tcp_ip_checksum_info *csum_info)
> {
> struct net_device *net;
> + struct net_device_context *net_device_ctx;
> struct sk_buff *skb;
> + struct netvsc_stats *rx_stats;
>
> net = ((struct netvsc_device *)hv_get_drvdata(device_obj))->ndev;
> if (!net || net->reg_state != NETREG_REGISTERED) {
> packet->status = NVSP_STAT_FAIL;
> return 0;
> }
> + net_device_ctx = netdev_priv(net);
> + rx_stats = this_cpu_ptr(net_device_ctx->rx_stats);
>
> /* Allocate a skb - TODO direct I/O to pages? */
> skb = netdev_alloc_skb_ip_align(net, packet->total_data_buflen);
> @@ -686,8 +692,10 @@ int netvsc_recv_callback(struct hv_device *device_obj,
> skb_record_rx_queue(skb, packet->channel->
> offermsg.offer.sub_channel_index);
>
> - net->stats.rx_packets++;
> - net->stats.rx_bytes += packet->total_data_buflen;
> + u64_stats_update_begin(&rx_stats->s_sync);
> + rx_stats->packets++;
> + rx_stats->bytes += packet->total_data_buflen;
> + u64_stats_update_end(&rx_stats->s_sync);
>
> /*
> * Pass the skb back up. Network stack will deallocate the skb when it
> @@ -753,6 +761,46 @@ static int netvsc_change_mtu(struct net_device *ndev, int mtu)
> return 0;
> }
>
> +static struct rtnl_link_stats64 *netvsc_get_stats64(struct net_device *net,
> + struct rtnl_link_stats64 *t)
> +{
> + struct net_device_context *ndev_ctx = netdev_priv(net);
> + int cpu;
> +
> + for_each_possible_cpu(cpu) {
> + struct netvsc_stats *tx_stats = per_cpu_ptr(ndev_ctx->tx_stats,
> + cpu);
> + struct netvsc_stats *rx_stats = per_cpu_ptr(ndev_ctx->rx_stats,
> + cpu);
> + u64 tx_packets, tx_bytes, rx_packets, rx_bytes;
> + unsigned int start;
> +
> + do {
> + start = u64_stats_fetch_begin_irq(&tx_stats->s_sync);
> + tx_packets = tx_stats->packets;
> + tx_bytes = tx_stats->bytes;
> + } while (u64_stats_fetch_retry_irq(&tx_stats->s_sync, start));
> +
> + do {
> + start = u64_stats_fetch_begin_irq(&rx_stats->s_sync);
> + rx_packets = rx_stats->packets;
> + rx_bytes = rx_stats->bytes;
> + } while (u64_stats_fetch_retry_irq(&rx_stats->s_sync, start));
> +
> + t->tx_bytes += tx_bytes;
> + t->tx_packets += tx_packets;
> + t->rx_bytes += rx_bytes;
> + t->rx_packets += rx_packets;
> + }
> +
> + t->tx_dropped = net->stats.tx_dropped;
> + t->tx_errors = net->stats.tx_dropped;
> +
> + t->rx_dropped = net->stats.rx_dropped;
> + t->rx_errors = net->stats.rx_errors;
> +
> + return t;
> +}
>
> static int netvsc_set_mac_addr(struct net_device *ndev, void *p)
> {
> @@ -804,6 +852,7 @@ static const struct net_device_ops device_ops = {
> .ndo_validate_addr = eth_validate_addr,
> .ndo_set_mac_address = netvsc_set_mac_addr,
> .ndo_select_queue = netvsc_select_queue,
> + .ndo_get_stats64 = netvsc_get_stats64,
> #ifdef CONFIG_NET_POLL_CONTROLLER
> .ndo_poll_controller = netvsc_poll_controller,
> #endif
> @@ -855,6 +904,14 @@ static void netvsc_link_change(struct work_struct *w)
> netdev_notify_peers(net);
> }
>
> +static void netvsc_free_netdev(struct net_device *netdev)
> +{
> + struct net_device_context *net_device_ctx = netdev_priv(netdev);
> +
> + free_percpu(net_device_ctx->tx_stats);
> + free_percpu(net_device_ctx->rx_stats);
> + free_netdev(netdev);
> +}
>
> static int netvsc_probe(struct hv_device *dev,
> const struct hv_vmbus_device_id *dev_id)
> @@ -883,6 +940,13 @@ static int netvsc_probe(struct hv_device *dev,
> netdev_dbg(net, "netvsc msg_enable: %d\n",
> net_device_ctx->msg_enable);
>
> + net_device_ctx->tx_stats = netdev_alloc_pcpu_stats(struct netvsc_stats);
> + if (!net_device_ctx->tx_stats)
> + return -ENOMEM;
> + net_device_ctx->rx_stats = netdev_alloc_pcpu_stats(struct netvsc_stats);
> + if (!net_device_ctx->rx_stats)
> + return -ENOMEM;
Both of these return statements leak.
The first one leaks the net_device, the second one leaks the net_device
and the ->tx_stats memory.
You have to have cleanup paths here.
--
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