Subject: Re: [net-next RFC PATCH] virtio_net: collect satistics and export through ethtool

From: "Michael S. Tsirkin" <[email-masked]>
Date: Wed, 6 Jun 2012 09:49:59 +0300

On Wed, Jun 06, 2012 at 01:02:19PM +0800, Jason Wang wrote:
> 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<[email-masked]>
> >>---
> >>  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.

Make offset be in units of sizeof u64 and you won't need
this hack.
Also, macro parameters must be surrounded with ().

> >>+			       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.

Yes but you can then open-code.

> >
> >>  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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