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Message-ID: <20140108182456.GC18162@redhat.com>
Date: Wed, 8 Jan 2014 20:24:56 +0200
From: "Michael S. Tsirkin" <mst@...hat.com>
To: Michael Dalton <mwdalton@...gle.com>
Cc: "David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
Eric Dumazet <edumazet@...gle.com>,
Rusty Russell <rusty@...tcorp.com.au>,
Jason Wang <jasowang@...hat.com>,
virtualization@...ts.linux-foundation.org
Subject: Re: [PATCH net-next v2 4/4] virtio-net: initial debugfs support,
export mergeable rx buffer size
On Mon, Jan 06, 2014 at 09:25:55PM -0800, Michael Dalton wrote:
> Add initial support for debugfs to virtio-net. Each virtio-net network
> device will have a directory under /virtio-net in debugfs. The
> per-network device directory will contain one sub-directory per active,
> enabled receive queue. If mergeable receive buffers are enabled, each
> receive queue directory will contain a read-only file that returns the
> current packet buffer size for the receive queue.
>
> Signed-off-by: Michael Dalton <mwdalton@...gle.com>
thanks, I'll play with it.
Could you tell us meanwhile, what's the typical size that you see?
> ---
> drivers/net/virtio_net.c | 314 ++++++++++++++++++++++++++++++++++++++++++++---
> 1 file changed, 296 insertions(+), 18 deletions(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index f6e1ee0..5da18d6 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -27,6 +27,9 @@
> #include <linux/slab.h>
> #include <linux/cpu.h>
> #include <linux/average.h>
> +#include <linux/seqlock.h>
> +#include <linux/kref.h>
> +#include <linux/debugfs.h>
>
> static int napi_weight = NAPI_POLL_WEIGHT;
> module_param(napi_weight, int, 0444);
> @@ -35,6 +38,9 @@ static bool csum = true, gso = true;
> module_param(csum, bool, 0444);
> module_param(gso, bool, 0444);
>
> +/* Debugfs root directory for all virtio-net devices. */
> +static struct dentry *virtnet_debugfs_root;
> +
> /* FIXME: MTU in config. */
> #define GOOD_PACKET_LEN (ETH_HLEN + VLAN_HLEN + ETH_DATA_LEN)
> #define GOOD_COPY_LEN 128
> @@ -102,9 +108,6 @@ struct receive_queue {
> /* Chain pages by the private ptr. */
> struct page *pages;
>
> - /* Average packet length for mergeable receive buffers. */
> - struct ewma mrg_avg_pkt_len;
> -
> /* Page frag for packet buffer allocation. */
> struct page_frag alloc_frag;
>
> @@ -115,6 +118,28 @@ struct receive_queue {
> char name[40];
> };
>
> +/* Per-receive queue statistics exported via debugfs. */
> +struct receive_queue_stats {
> + /* Average packet length of receive queue (for mergeable rx buffers). */
> + struct ewma avg_pkt_len;
> +
> + /* Per-receive queue stats debugfs directory. */
> + struct dentry *dbg;
> +
> + /* Reference count for the receive queue statistics, needed because
> + * an open debugfs file may outlive the receive queue and netdevice.
> + * Open files will remain in-use until all outstanding file descriptors
> + * are closed, even after the underlying file is unlinked.
> + */
> + struct kref refcount;
> +
> + /* Sequence counter to allow debugfs readers to safely access stats.
> + * Assumes a single virtio-net writer, which is enforced by virtio-net
> + * and NAPI.
> + */
> + seqcount_t dbg_seq;
> +};
> +
> struct virtnet_info {
> struct virtio_device *vdev;
> struct virtqueue *cvq;
> @@ -147,6 +172,15 @@ struct virtnet_info {
> /* Active statistics */
> struct virtnet_stats __percpu *stats;
>
> + /* Per-receive queue statstics exported via debugfs. Stored in
> + * virtnet_info to survive freeze/restore -- a task may have a per-rq
> + * debugfs file open at the time of freeze.
> + */
> + struct receive_queue_stats **rq_stats;
> +
> + /* Per-netdevice debugfs directory. */
> + struct dentry *dbg_dev_root;
> +
> /* Work struct for refilling if we run low on memory. */
> struct delayed_work refill;
>
> @@ -358,6 +392,8 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
> unsigned int len)
> {
> struct skb_vnet_hdr *hdr = ctx->buf;
> + struct virtnet_info *vi = netdev_priv(dev);
> + struct receive_queue_stats *rq_stats = vi->rq_stats[vq2rxq(rq->vq)];
> int num_buf = hdr->mhdr.num_buffers;
> struct page *page = virt_to_head_page(ctx->buf);
> int offset = ctx->buf - page_address(page);
> @@ -413,7 +449,9 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
> }
> }
>
> - ewma_add(&rq->mrg_avg_pkt_len, head_skb->len);
> + write_seqcount_begin(&rq_stats->dbg_seq);
> + ewma_add(&rq_stats->avg_pkt_len, head_skb->len);
> + write_seqcount_end(&rq_stats->dbg_seq);
> return head_skb;
>
> err_skb:
> @@ -600,18 +638,30 @@ static int add_recvbuf_big(struct receive_queue *rq, gfp_t gfp)
> return err;
> }
>
> +static unsigned int get_mergeable_buf_len(struct ewma *avg_pkt_len)
> +{
> + const size_t hdr_len = sizeof(struct virtio_net_hdr_mrg_rxbuf);
> + unsigned int len;
> +
> + len = hdr_len + clamp_t(unsigned int, ewma_read(avg_pkt_len),
> + GOOD_PACKET_LEN, PAGE_SIZE - hdr_len);
> + return ALIGN(len, L1_CACHE_BYTES);
> +}
> +
> static int add_recvbuf_mergeable(struct receive_queue *rq, gfp_t gfp)
> {
> const unsigned int ring_size = rq->mrg_buf_ctx_size;
> - const size_t hdr_len = sizeof(struct virtio_net_hdr_mrg_rxbuf);
> struct page_frag *alloc_frag = &rq->alloc_frag;
> + struct virtnet_info *vi = rq->vq->vdev->priv;
> struct mergeable_receive_buf_ctx *ctx;
> int err;
> unsigned int len, hole;
>
> - len = hdr_len + clamp_t(unsigned int, ewma_read(&rq->mrg_avg_pkt_len),
> - GOOD_PACKET_LEN, PAGE_SIZE - hdr_len);
> - len = ALIGN(len, L1_CACHE_BYTES);
> + /* avg_pkt_len is written only in NAPI rx softirq context. We may
> + * read avg_pkt_len without using the dbg_seq seqcount, as this code
> + * is called only in NAPI rx softirq context or when NAPI is disabled.
> + */
> + len = get_mergeable_buf_len(&vi->rq_stats[vq2rxq(rq->vq)]->avg_pkt_len);
> if (unlikely(!skb_page_frag_refill(len, alloc_frag, gfp)))
> return -ENOMEM;
>
> @@ -1274,13 +1324,101 @@ static void virtnet_get_drvinfo(struct net_device *dev,
>
> }
>
> +static ssize_t mergeable_rx_buffer_size_read(struct file *file,
> + char __user *userbuf,
> + size_t count,
> + loff_t *ppos)
> +{
> + struct receive_queue_stats *rq_stats = file->private_data;
> + char buf[32];
> + struct ewma avg;
> + unsigned int start, len;
> +
> + /* Don't allow partial reads. */
> + if (*ppos)
> + return 0;
> + do {
> + start = read_seqcount_begin(&rq_stats->dbg_seq);
> + avg = rq_stats->avg_pkt_len;
> + } while (read_seqcount_retry(&rq_stats->dbg_seq, start));
> + len = scnprintf(buf, sizeof(buf), "%u\n", get_mergeable_buf_len(&avg));
> + return simple_read_from_buffer(userbuf, count, ppos, buf, len);
> +}
> +
> +void receive_queue_stats_free(struct kref *ref)
> +{
> + struct receive_queue_stats *rq_stats;
> +
> + rq_stats = container_of(ref, struct receive_queue_stats, refcount);
> + kfree(rq_stats);
> +}
> +
> +static int receive_queue_stats_debugfs_open(struct inode *inode,
> + struct file *file)
> +{
> + struct receive_queue_stats *rq_stats = inode->i_private;
> + kref_get(&rq_stats->refcount);
> + file->private_data = rq_stats;
> + return 0;
> +}
> +
> +static int receive_queue_stats_debugfs_release(struct inode *inode,
> + struct file *file)
> +{
> + struct receive_queue_stats *rq_stats = inode->i_private;
> + kref_put(&rq_stats->refcount, receive_queue_stats_free);
> + file->private_data = NULL;
> + return 0;
> +}
> +
> +static const struct file_operations mergeable_rx_buffer_size_fops = {
> + .owner = THIS_MODULE,
> + .open = receive_queue_stats_debugfs_open,
> + .read = mergeable_rx_buffer_size_read,
> + .llseek = default_llseek,
> + .release = receive_queue_stats_debugfs_release,
> +};
> +
> +static void receive_queue_debugfs_add(struct receive_queue *rq)
> +{
> + struct virtnet_info *vi = rq->vq->vdev->priv;
> + unsigned int rq_index = vq2rxq(rq->vq);
> + struct receive_queue_stats *rq_stats = vi->rq_stats[rq_index];
> + struct dentry *dentry;
> + char name[32];
> +
> + if (IS_ERR_OR_NULL(vi->dbg_dev_root))
> + return;
> + scnprintf(name, sizeof(name), "rx-%u", rq_index);
> + dentry = debugfs_create_dir(name, vi->dbg_dev_root);
> + if (IS_ERR_OR_NULL(dentry)) {
> + pr_warn("%s: could not create %s rx queue debugfs dir\n",
> + vi->dev->name, name);
> + return;
> + }
> + rq_stats->dbg = dentry;
> + if (vi->mergeable_rx_bufs)
> + debugfs_create_file("mergeable_rx_buffer_size", S_IRUSR,
> + rq_stats->dbg, rq_stats,
> + &mergeable_rx_buffer_size_fops);
> +}
> +
> +static void receive_queue_debugfs_del(struct receive_queue *rq)
> +{
> + struct virtnet_info *vi = rq->vq->vdev->priv;
> + struct receive_queue_stats *rq_stats = vi->rq_stats[vq2rxq(rq->vq)];
> + debugfs_remove_recursive(rq_stats->dbg);
> + rq_stats->dbg = NULL;
> +}
> +
> /* TODO: Eliminate OOO packets during switching */
> static int virtnet_set_channels(struct net_device *dev,
> struct ethtool_channels *channels)
> {
> struct virtnet_info *vi = netdev_priv(dev);
> - u16 queue_pairs = channels->combined_count;
> - int err;
> + u16 new_queue_pairs = channels->combined_count;
> + u16 old_queue_pairs = vi->curr_queue_pairs;
> + int err, i;
>
> /* We don't support separate rx/tx channels.
> * We don't allow setting 'other' channels.
> @@ -1288,14 +1426,21 @@ static int virtnet_set_channels(struct net_device *dev,
> if (channels->rx_count || channels->tx_count || channels->other_count)
> return -EINVAL;
>
> - if (queue_pairs > vi->max_queue_pairs)
> + if (new_queue_pairs > vi->max_queue_pairs)
> return -EINVAL;
>
> get_online_cpus();
> - err = virtnet_set_queues(vi, queue_pairs);
> + err = virtnet_set_queues(vi, new_queue_pairs);
> if (!err) {
> - netif_set_real_num_tx_queues(dev, queue_pairs);
> - netif_set_real_num_rx_queues(dev, queue_pairs);
> + if (new_queue_pairs < old_queue_pairs) {
> + for (i = new_queue_pairs; i < old_queue_pairs; i++)
> + receive_queue_debugfs_del(&vi->rq[i]);
> + } else {
> + for (i = old_queue_pairs; i < new_queue_pairs; i++)
> + receive_queue_debugfs_add(&vi->rq[i]);
> + }
> + netif_set_real_num_tx_queues(dev, new_queue_pairs);
> + netif_set_real_num_rx_queues(dev, new_queue_pairs);
>
> virtnet_set_affinity(vi);
> }
> @@ -1336,7 +1481,44 @@ static int virtnet_change_mtu(struct net_device *dev, int new_mtu)
> return 0;
> }
>
> +/* Must be called only after the net_device name has been expanded. */
> +static void virtnet_debugfs_init(struct virtnet_info *vi)
> +{
> + int i;
> +
> + if (IS_ERR_OR_NULL(virtnet_debugfs_root))
> + return;
> + vi->dbg_dev_root = debugfs_create_dir(vi->dev->name,
> + virtnet_debugfs_root);
> + if (IS_ERR_OR_NULL(vi->dbg_dev_root)) {
> + pr_warn("%s: could not create netdevice debugfs dir\n",
> + vi->dev->name);
> + return;
> + }
> + for (i = 0; i < vi->curr_queue_pairs; i++)
> + receive_queue_debugfs_add(&vi->rq[i]);
> +}
> +
> +static void virtnet_debugfs_cleanup(struct virtnet_info *vi)
> +{
> + int i;
> +
> + for (i = 0; i < vi->max_queue_pairs; i++)
> + receive_queue_debugfs_del(&vi->rq[i]);
> + debugfs_remove_recursive(vi->dbg_dev_root);
> + vi->dbg_dev_root = NULL;
> +}
> +
> +static int virtnet_init(struct net_device *dev)
> +{
> + struct virtnet_info *vi = netdev_priv(dev);
> +
> + virtnet_debugfs_init(vi);
> + return 0;
> +}
> +
> static const struct net_device_ops virtnet_netdev = {
> + .ndo_init = virtnet_init,
> .ndo_open = virtnet_open,
> .ndo_stop = virtnet_close,
> .ndo_start_xmit = start_xmit,
> @@ -1560,7 +1742,6 @@ static int virtnet_alloc_queues(struct virtnet_info *vi)
> napi_weight);
>
> sg_init_table(vi->rq[i].sg, ARRAY_SIZE(vi->rq[i].sg));
> - ewma_init(&vi->rq[i].mrg_avg_pkt_len, 1, RECEIVE_AVG_WEIGHT);
> sg_init_table(vi->sq[i].sg, ARRAY_SIZE(vi->sq[i].sg));
> }
>
> @@ -1614,6 +1795,39 @@ err:
> return ret;
> }
>
> +static int virtnet_rename(struct notifier_block *this,
> + unsigned long event, void *ptr)
> +{
> + struct net_device *dev = netdev_notifier_info_to_dev(ptr);
> + struct virtnet_info *vi;
> +
> + if (event != NETDEV_CHANGENAME || dev->netdev_ops != &virtnet_netdev)
> + return NOTIFY_DONE;
> + vi = netdev_priv(dev);
> + if (IS_ERR_OR_NULL(vi->dbg_dev_root))
> + return NOTIFY_DONE;
> + if (IS_ERR_OR_NULL(debugfs_rename(virtnet_debugfs_root,
> + vi->dbg_dev_root,
> + virtnet_debugfs_root, dev->name))) {
> + pr_warn("%s: failed debugfs rename, removing old debugfs dir\n",
> + dev->name);
> + virtnet_debugfs_cleanup(vi);
> + }
> + return NOTIFY_DONE;
> +}
> +
> +static void virtnet_release_receive_queue_stats(struct virtnet_info *vi)
> +{
> + int i;
> +
> + for (i = 0; i < vi->max_queue_pairs; i++) {
> + struct receive_queue_stats *rq_stats = vi->rq_stats[i];
> + if (rq_stats)
> + kref_put(&rq_stats->refcount, receive_queue_stats_free);
> + }
> + kfree(vi->rq_stats);
> +}
> +
> static int virtnet_probe(struct virtio_device *vdev)
> {
> int i, err;
> @@ -1723,10 +1937,24 @@ static int virtnet_probe(struct virtio_device *vdev)
> vi->curr_queue_pairs = 1;
> vi->max_queue_pairs = max_queue_pairs;
>
> + vi->rq_stats = kzalloc(sizeof(vi->rq_stats[0]) *
> + vi->max_queue_pairs, GFP_KERNEL);
> + if (!vi->rq_stats)
> + goto free_dev_stats;
> + for (i = 0; i < vi->max_queue_pairs; i++) {
> + vi->rq_stats[i] = kzalloc(sizeof(*vi->rq_stats[0]), GFP_KERNEL);
> + if (!vi->rq_stats[i])
> + goto free_rq_stats;
> + seqcount_init(&vi->rq_stats[i]->dbg_seq);
> + kref_init(&vi->rq_stats[i]->refcount);
> + ewma_init(&vi->rq_stats[i]->avg_pkt_len, 1,
> + RECEIVE_AVG_WEIGHT);
> + }
> +
> /* Allocate/initialize the rx/tx queues, and invoke find_vqs */
> err = init_vqs(vi);
> if (err)
> - goto free_stats;
> + goto free_rq_stats;
>
> netif_set_real_num_tx_queues(dev, vi->curr_queue_pairs);
> netif_set_real_num_rx_queues(dev, vi->curr_queue_pairs);
> @@ -1777,8 +2005,11 @@ free_recv_bufs:
> free_vqs:
> cancel_delayed_work_sync(&vi->refill);
> free_receive_page_frags(vi);
> + virtnet_debugfs_cleanup(vi);
> virtnet_del_vqs(vi);
> -free_stats:
> +free_rq_stats:
> + virtnet_release_receive_queue_stats(vi);
> +free_dev_stats:
> free_percpu(vi->stats);
> free:
> free_netdev(dev);
> @@ -1812,10 +2043,12 @@ static void virtnet_remove(struct virtio_device *vdev)
>
> unregister_netdev(vi->dev);
>
> + virtnet_debugfs_cleanup(vi);
> remove_vq_common(vi);
>
> flush_work(&vi->config_work);
>
> + virtnet_release_receive_queue_stats(vi);
> free_percpu(vi->stats);
> free_netdev(vi->dev);
> }
> @@ -1884,6 +2117,19 @@ static int virtnet_restore(struct virtio_device *vdev)
> }
> #endif
>
> +static void virtnet_register_debugfs(void)
> +{
> + virtnet_debugfs_root = debugfs_create_dir("virtio-net", NULL);
> + if (IS_ERR_OR_NULL(virtnet_debugfs_root))
> + pr_warn("Could not create virtio-net debugfs dir\n");
> +}
> +
> +static void virtnet_unregister_debugfs(void)
> +{
> + debugfs_remove_recursive(virtnet_debugfs_root);
> + virtnet_debugfs_root = NULL;
> +}
> +
> static struct virtio_device_id id_table[] = {
> { VIRTIO_ID_NET, VIRTIO_DEV_ANY_ID },
> { 0 },
> @@ -1917,7 +2163,39 @@ static struct virtio_driver virtio_net_driver = {
> #endif
> };
>
> -module_virtio_driver(virtio_net_driver);
> +static struct notifier_block virtnet_rename_notifier = {
> + .notifier_call = virtnet_rename,
> +};
> +
> +static int __init init(void)
> +{
> + int err;
> +
> + virtnet_register_debugfs();
> + err = register_netdevice_notifier(&virtnet_rename_notifier);
> + if (err)
> + goto free_debugfs;
> + err = register_virtio_driver(&virtio_net_driver);
> + if (err)
> + goto free_notifier;
> + return 0;
> +
> +free_notifier:
> + unregister_netdevice_notifier(&virtnet_rename_notifier);
> +free_debugfs:
> + virtnet_unregister_debugfs();
> + return err;
> +}
> +
> +static void __exit cleanup(void)
> +{
> + unregister_virtio_driver(&virtio_net_driver);
> + unregister_netdevice_notifier(&virtnet_rename_notifier);
> + virtnet_unregister_debugfs();
> +}
> +
> +module_init(init);
> +module_exit(cleanup);
>
> MODULE_DEVICE_TABLE(virtio, id_table);
> MODULE_DESCRIPTION("Virtio network driver");
> --
> 1.8.5.1
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