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Date: Thu, 16 Jan 2014 01:38:46 -0800
From: Michael Dalton <mwdalton@...gle.com>
To: "David S. Miller" <davem@...emloft.net>
Cc: netdev@...r.kernel.org, Eric Dumazet <edumazet@...gle.com>,
Rusty Russell <rusty@...tcorp.com.au>,
"Michael S. Tsirkin" <mst@...hat.com>,
Jason Wang <jasowang@...hat.com>,
virtualization@...ts.linux-foundation.org,
Michael Dalton <mwdalton@...gle.com>
Subject: [PATCH net-next v3 5/5] virtio-net: initial rx sysfs support, export mergeable rx buffer size
Add initial support for per-rx queue sysfs attributes to virtio-net. If
mergeable packet buffers are enabled, adds a read-only mergeable packet
buffer size sysfs attribute for each RX queue.
Signed-off-by: Michael Dalton <mwdalton@...gle.com>
---
drivers/net/virtio_net.c | 66 +++++++++++++++++++++++++++++++++++++++++++++---
1 file changed, 62 insertions(+), 4 deletions(-)
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 3e82311..f315cbb 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -27,6 +27,7 @@
#include <linux/slab.h>
#include <linux/cpu.h>
#include <linux/average.h>
+#include <linux/seqlock.h>
static int napi_weight = NAPI_POLL_WEIGHT;
module_param(napi_weight, int, 0444);
@@ -89,6 +90,12 @@ struct receive_queue {
/* Average packet length for mergeable receive buffers. */
struct ewma mrg_avg_pkt_len;
+ /* Sequence counter to allow sysfs readers to safely access stats.
+ * Assumes a single virtio-net writer, which is enforced by virtio-net
+ * and NAPI.
+ */
+ seqcount_t sysfs_seq;
+
/* Page frag for packet buffer allocation. */
struct page_frag alloc_frag;
@@ -416,7 +423,9 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
}
}
+ write_seqcount_begin(&rq->sysfs_seq);
ewma_add(&rq->mrg_avg_pkt_len, head_skb->len);
+ write_seqcount_end(&rq->sysfs_seq);
return head_skb;
err_skb:
@@ -604,18 +613,29 @@ static int add_recvbuf_big(struct receive_queue *rq, gfp_t gfp)
return err;
}
-static int add_recvbuf_mergeable(struct receive_queue *rq, gfp_t gfp)
+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, MERGEABLE_BUFFER_ALIGN);
+}
+
+static int add_recvbuf_mergeable(struct receive_queue *rq, gfp_t gfp)
+{
struct page_frag *alloc_frag = &rq->alloc_frag;
char *buf;
unsigned long 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, MERGEABLE_BUFFER_ALIGN);
+ /* avg_pkt_len is written only in NAPI rx softirq context. We may
+ * read avg_pkt_len without using the sysfs_seq seqcount, as this code
+ * is called only in NAPI rx softirq context or when NAPI is disabled.
+ */
+ len = get_mergeable_buf_len(&rq->mrg_avg_pkt_len);
if (unlikely(!skb_page_frag_refill(len, alloc_frag, gfp)))
return -ENOMEM;
@@ -1557,6 +1577,7 @@ static int virtnet_alloc_queues(struct virtnet_info *vi)
napi_weight);
sg_init_table(vi->rq[i].sg, ARRAY_SIZE(vi->rq[i].sg));
+ seqcount_init(&vi->rq[i].sysfs_seq);
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));
}
@@ -1594,6 +1615,39 @@ err:
return ret;
}
+#ifdef CONFIG_SYSFS
+static ssize_t mergeable_rx_buffer_size_show(struct netdev_rx_queue *queue,
+ struct rx_queue_attribute *attribute, char *buf)
+{
+ struct virtnet_info *vi = netdev_priv(queue->dev);
+ unsigned int queue_index = get_netdev_rx_queue_index(queue);
+ struct receive_queue *rq;
+ struct ewma avg;
+ unsigned int start;
+
+ BUG_ON(queue_index >= vi->max_queue_pairs);
+ rq = &vi->rq[queue_index];
+ do {
+ start = read_seqcount_begin(&rq->sysfs_seq);
+ avg = rq->mrg_avg_pkt_len;
+ } while (read_seqcount_retry(&rq->sysfs_seq, start));
+ return sprintf(buf, "%u\n", get_mergeable_buf_len(&avg));
+}
+
+static struct rx_queue_attribute mergeable_rx_buffer_size_attribute =
+ __ATTR_RO(mergeable_rx_buffer_size);
+
+static struct attribute *virtio_net_mrg_rx_attrs[] = {
+ &mergeable_rx_buffer_size_attribute.attr,
+ NULL
+};
+
+static const struct attribute_group virtio_net_mrg_rx_group = {
+ .name = "virtio_net",
+ .attrs = virtio_net_mrg_rx_attrs
+};
+#endif
+
static int virtnet_probe(struct virtio_device *vdev)
{
int i, err;
@@ -1708,6 +1762,10 @@ static int virtnet_probe(struct virtio_device *vdev)
if (err)
goto free_stats;
+#ifdef CONFIG_SYSFS
+ if (vi->mergeable_rx_bufs)
+ dev->sysfs_rx_queue_group = &virtio_net_mrg_rx_group;
+#endif
netif_set_real_num_tx_queues(dev, vi->curr_queue_pairs);
netif_set_real_num_rx_queues(dev, vi->curr_queue_pairs);
--
1.8.5.2
--
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