Date:	Wed, 06 Jun 2012 13:02:19 +0800
From:	Jason Wang <jasowang@...hat.com>
To:	"Michael S. Tsirkin" <mst@...hat.com>
CC:	netdev@...r.kernel.org, rusty@...tcorp.com.au,
	virtualization@...ts.linux-foundation.org,
	linux-kernel@...r.kernel.org
Subject: Re: [net-next RFC PATCH] virtio_net: collect satistics and export
 through ethtool

On 06/05/2012 06:10 PM, Michael S. Tsirkin wrote:
> On Tue, Jun 05, 2012 at 04:38:41PM +0800, Jason Wang wrote:
>> Satistics counters is useful for debugging and performance optimization, so this
>> patch lets virtio_net driver collect following and export them to userspace
>> through "ethtool -S":
>>
>> - number of packets sent/received
>> - number of bytes sent/received
>> - number of callbacks for tx/rx
>> - number of kick for tx/rx
>> - number of bytes/packets queued for tx
>>
>> As virtnet_stats were per-cpu, so both per-cpu and gloabl satistics were exposed
>> like:
>>
>> NIC statistics:
>>       tx_bytes[0]: 2551
>>       tx_packets[0]: 12
>>       tx_kick[0]: 12
>>       tx_callbacks[0]: 1
>>       tx_queued_packets[0]: 12
>>       tx_queued_bytes[0]: 3055
>>       rx_bytes[0]: 0
>>       rx_packets[0]: 0
>>       rx_kick[0]: 0
>>       rx_callbacks[0]: 0
>>       tx_bytes[1]: 5575
>>       tx_packets[1]: 37
>>       tx_kick[1]: 38
>>       tx_callbacks[1]: 0
>>       tx_queued_packets[1]: 38
>>       tx_queued_bytes[1]: 5217
>>       rx_bytes[1]: 4175
>>       rx_packets[1]: 25
>>       rx_kick[1]: 1
>>       rx_callbacks[1]: 16
>>       tx_bytes: 8126
>>       tx_packets: 49
>>       tx_kick: 50
>>       tx_callbacks: 1
>>       tx_queued_packets: 50
>>       tx_queued_bytes: 8272
>>       rx_bytes: 4175
>>       rx_packets: 25
>>       rx_kick: 1
>>       rx_callbacks: 16
>>
>> TODO:
>>
>> - more satistics
>> - unitfy the ndo_get_stats64 and get_ethtool_stats
>> - calculate the pending bytes/pkts
>>
>> Signed-off-by: Jason Wang<jasowang@...hat.com>
>> ---
>>   drivers/net/virtio_net.c |  130 +++++++++++++++++++++++++++++++++++++++++++++-
>>   1 files changed, 127 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
>> index 5214b1e..7ab0cc1 100644
>> --- a/drivers/net/virtio_net.c
>> +++ b/drivers/net/virtio_net.c
>> @@ -41,6 +41,10 @@ module_param(gso, bool, 0444);
>>   #define VIRTNET_SEND_COMMAND_SG_MAX    2
>>   #define VIRTNET_DRIVER_VERSION "1.0.0"
>>
>> +#define VIRTNET_STAT_OFF(m) offsetof(struct virtnet_stats, m)
>> +#define VIRTNET_STAT(stat, i) (*((u64 *)((char *)stat + \
> What's going on? Why cast to char *?

It's used to let the pointer advance at the unit of bytes instead of the 
whole stat strcuture.
>> +			       virtnet_stats_str_attr[i].stat_offset)))
> These are confusing unless you see what virtnet_stats_str_attr
> is so please move them near that definition.

ok.
>> +
>>   struct virtnet_stats {
>>   	struct u64_stats_sync syncp;
>>   	u64 tx_bytes;
>> @@ -48,8 +52,33 @@ struct virtnet_stats {
>>
>>   	u64 rx_bytes;
>>   	u64 rx_packets;
>> +
>> +	u64 tx_kick;
>> +	u64 rx_kick;
>> +	u64 tx_callbacks;
>> +	u64 rx_callbacks;
>> +	u64 tx_queued_packets;
>> +	u64 tx_queued_bytes;
>> +};
> I have an idea (not a must): why don't we simply create an enum
> enum virtnet_stats {
> 	VIRTNET_TX_KICK,
> 	VIRTNET_RX_KICK,
> 	....
> 	VIRTNET_MAX_STAT,
> }
>
>
> now stats can just do
> 	stats->data[VIRTNET_RX_KICK] instead of stats->rx_kick
> which is not a big problem, but copying them in bulk
> becomes straight-forward, no need for macros at all.
>
> If we decide to do this, needs to be a separate patch,
> then this one on top.

Make sense, would do this.
>> +
>> +static struct {
> static const.
>
>> +	char string[ETH_GSTRING_LEN];
>> +	int stat_offset;
>> +} virtnet_stats_str_attr[] = {
>> +	{ "tx_bytes", VIRTNET_STAT_OFF(tx_bytes)},
>> +	{ "tx_packets", VIRTNET_STAT_OFF(tx_packets)},
>> +	{ "tx_kick", VIRTNET_STAT_OFF(tx_kick)},
>> +	{ "tx_callbacks", VIRTNET_STAT_OFF(tx_callbacks)},
>> +	{ "tx_queued_packets", VIRTNET_STAT_OFF(tx_queued_packets)},
>> +	{ "tx_queued_bytes", VIRTNET_STAT_OFF(tx_queued_bytes)},
>> +	{ "rx_bytes" , VIRTNET_STAT_OFF(rx_bytes)},
>> +	{ "rx_packets", VIRTNET_STAT_OFF(rx_packets)},
>> +	{ "rx_kick", VIRTNET_STAT_OFF(rx_kick)},
>> +	{ "rx_callbacks", VIRTNET_STAT_OFF(rx_callbacks)},
> VIRTNET_STAT_OFF does not save much here, but if you are after
> saving characters then make the macro instanciate the string
> as well.
>
>>   };
>>
>> +#define VIRTNET_NUM_STATS ARRAY_SIZE(virtnet_stats_str_attr)
>> +
> if you pass virtnet_stats_str_attr to VIRTNET_STAT macro,
> then it's explicit and VIRTNET_NUM_STATS won't be needed either.

It's used to report the number of satistics through .get_sset_count.
>
>>   struct virtnet_info {
>>   	struct virtio_device *vdev;
>>   	struct virtqueue *rvq, *svq, *cvq;
>> @@ -142,6 +171,11 @@ static struct page *get_a_page(struct virtnet_info *vi, gfp_t gfp_mask)
>>   static void skb_xmit_done(struct virtqueue *svq)
>>   {
>>   	struct virtnet_info *vi = svq->vdev->priv;
>> +	struct virtnet_stats *stats = this_cpu_ptr(vi->stats);
>> +
>> +	u64_stats_update_begin(&stats->syncp);
>> +	stats->tx_callbacks++;
>> +	u64_stats_update_end(&stats->syncp);
>>
>>   	/* Suppress further interrupts. */
>>   	virtqueue_disable_cb(svq);
>> @@ -461,6 +495,7 @@ static bool try_fill_recv(struct virtnet_info *vi, gfp_t gfp)
>>   {
>>   	int err;
>>   	bool oom;
>> +	struct virtnet_stats *stats = this_cpu_ptr(vi->stats);
>>
>>   	do {
>>   		if (vi->mergeable_rx_bufs)
>> @@ -477,13 +512,24 @@ static bool try_fill_recv(struct virtnet_info *vi, gfp_t gfp)
>>   	} while (err>  0);
>>   	if (unlikely(vi->num>  vi->max))
>>   		vi->max = vi->num;
>> -	virtqueue_kick(vi->rvq);
>> +	if (virtqueue_kick_prepare(vi->rvq)) {
>> +		virtqueue_notify(vi->rvq);
>> +		u64_stats_update_begin(&stats->syncp);
>> +		stats->rx_kick++;
>> +		u64_stats_update_end(&stats->syncp);
>> +	}
>>   	return !oom;
>>   }
>>
>>   static void skb_recv_done(struct virtqueue *rvq)
>>   {
>>   	struct virtnet_info *vi = rvq->vdev->priv;
>> +	struct virtnet_stats *stats = this_cpu_ptr(vi->stats);
>> +
>> +	u64_stats_update_begin(&stats->syncp);
>> +	stats->rx_callbacks++;
>> +	u64_stats_update_end(&stats->syncp);
>> +
>>   	/* Schedule NAPI, Suppress further interrupts if successful. */
>>   	if (napi_schedule_prep(&vi->napi)) {
>>   		virtqueue_disable_cb(rvq);
>> @@ -626,7 +672,9 @@ static int xmit_skb(struct virtnet_info *vi, struct sk_buff *skb)
>>   static netdev_tx_t start_xmit(struct sk_buff *skb, struct net_device *dev)
>>   {
>>   	struct virtnet_info *vi = netdev_priv(dev);
>> +	struct virtnet_stats *stats = this_cpu_ptr(vi->stats);
>>   	int capacity;
>> +	bool kick;
>>
>>   	/* Free up any pending old buffers before queueing new ones. */
>>   	free_old_xmit_skbs(vi);
>> @@ -651,7 +699,17 @@ static netdev_tx_t start_xmit(struct sk_buff *skb, struct net_device *dev)
>>   		kfree_skb(skb);
>>   		return NETDEV_TX_OK;
>>   	}
>> -	virtqueue_kick(vi->svq);
>> +
>> +	kick = virtqueue_kick_prepare(vi->svq);
>> +	if (kick)
> probably
> 	 if (unlikely(kick))
>
>> +		virtqueue_notify(vi->svq);
>> +
>> +	u64_stats_update_begin(&stats->syncp);
>> +	if (kick)
> this too
>
>> +		stats->tx_kick++;
>> +	stats->tx_queued_bytes += skb->len;
>> +	stats->tx_queued_packets++;
>> +	u64_stats_update_end(&stats->syncp);
>>
>>   	/* Don't wait up for transmitted skbs to be freed. */
>>   	skb_orphan(skb);
>> @@ -926,7 +984,6 @@ static void virtnet_get_ringparam(struct net_device *dev,
>>
>>   }
>>
>> -
>>   static void virtnet_get_drvinfo(struct net_device *dev,
>>   				struct ethtool_drvinfo *info)
>>   {
>> @@ -939,10 +996,77 @@ static void virtnet_get_drvinfo(struct net_device *dev,
>>
>>   }
>>
>> +static void virtnet_get_strings(struct net_device *dev, u32 stringset, u8 *buf)
>> +{
>> +	int i, cpu;
>> +	switch (stringset) {
>> +	case ETH_SS_STATS:
>> +		for_each_possible_cpu(cpu)
>> +			for (i = 0; i<  VIRTNET_NUM_STATS; i++) {
>> +				sprintf(buf, "%s[%u]",
>> +					virtnet_stats_str_attr[i].string, cpu);
>> +				buf += ETH_GSTRING_LEN;
>> +			}
>> +		for (i = 0; i<  VIRTNET_NUM_STATS; i++) {
>> +			memcpy(buf, virtnet_stats_str_attr[i].string,
>> +				ETH_GSTRING_LEN);
>> +			buf += ETH_GSTRING_LEN;
>> +		}
>> +		break;
>> +	}
>> +}
>> +
>> +static int virtnet_get_sset_count(struct net_device *dev, int sset)
>> +{
>> +	switch (sset) {
>> +	case ETH_SS_STATS:
>> +		return VIRTNET_NUM_STATS * (num_online_cpus() + 1);
> This will allocate buffers for online cpus only, but the above
> will fill them in for all possible cpus.
> Will this overrun some buffer?
>

Yes, a typo here, should be num_possible_cpus().
Thanks
>> +	default:
>> +		return -EOPNOTSUPP;
>> +	}
>> +}
>> +
>> +static void virtnet_get_ethtool_stats(struct net_device *dev,
>> +				struct ethtool_stats *stats, u64 *buf)
> The coding style says
> 	Descendants are always substantially shorter than the parent and
> 	are placed substantially to the right.
>
> you can't call it substantially to the right if it's to the left of
> the opening '('  :), so please indent it aligning on the opening.

Looks like something wrong in my emacs c-style confiugration, would 
check it.
>> +{
>> +	struct virtnet_info *vi = netdev_priv(dev);
>> +	int cpu, i;
>> +	unsigned int start;
>> +	struct virtnet_stats sample, total;
>> +
>> +	memset(&total, 0, sizeof(total));
>> +	memset(&sample, 0, sizeof(sample));
>> +
>> +	for_each_possible_cpu(cpu) {
>> +		struct virtnet_stats *stats = per_cpu_ptr(vi->stats, cpu);
>> +		do {
>> +			start = u64_stats_fetch_begin(&stats->syncp);
>> +			for (i = 0; i<  VIRTNET_NUM_STATS; i++) {
>> +				VIRTNET_STAT(&sample, i) =
>> +					VIRTNET_STAT(stats, i);
> when you feel the need to break lines like this - don't :)
> use an inline function instead.
>
>> +
> kill empty line here
>> +			}
> don't put {} around single statements pls.

Sure
>> +		} while (u64_stats_fetch_retry(&stats->syncp, start));
>> +		for (i = 0; i<  VIRTNET_NUM_STATS; i++) {
>> +			*buf = VIRTNET_STAT(&sample, i);
>> +			VIRTNET_STAT(&total, i) += VIRTNET_STAT(stats, i);
>> +			buf++;
>> +		}
>> +	}
>> +
>> +	for (i = 0; i<  VIRTNET_NUM_STATS; i++) {
>> +		*buf = VIRTNET_STAT(&total, i);
>> +		buf++;
>> +	}
>> +}
>> +
>>   static const struct ethtool_ops virtnet_ethtool_ops = {
>>   	.get_drvinfo = virtnet_get_drvinfo,
>>   	.get_link = ethtool_op_get_link,
>>   	.get_ringparam = virtnet_get_ringparam,
>> +	.get_ethtool_stats = virtnet_get_ethtool_stats,
>> +	.get_strings = virtnet_get_strings,
>> +	.get_sset_count = virtnet_get_sset_count,
>>   };
>>
>>   #define MIN_MTU 68
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