Re: [PATCH v2] virtio_net: fix support for small rings
On 2017年03月30日 01:42, Michael S. Tsirkin wrote:
When ring size is small (<32 entries) making buffers smaller means a
full ring might not be able to hold enough buffers to fit a single large
packet.
Make sure a ring full of buffers is large enough to allow at least one
packet of max size.
Fixes: 2613af0ed18a ("virtio_net: migrate mergeable rx buffers to page frag
allocators")
Signed-off-by: Michael S. Tsirkin
---
changes from v1:
typo fix
drivers/net/virtio_net.c | 30 ++
1 file changed, 26 insertions(+), 4 deletions(-)
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 9dc31dc..e5f6e34 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -29,6 +29,7 @@
#include
#include
#include
+#include
This seems unnecessary.
static int napi_weight = NAPI_POLL_WEIGHT;
module_param(napi_weight, int, 0444);
@@ -98,6 +99,9 @@ struct receive_queue {
/* RX: fragments + linear part + virtio header */
struct scatterlist sg[MAX_SKB_FRAGS + 2];
+ /* Min single buffer size for mergeable buffers case. */
+ unsigned int min_buf_len;
+
/* Name of this receive queue: input.$index */
char name[40];
};
@@ -894,13 +898,14 @@ static int add_recvbuf_big(struct virtnet_info *vi,
struct receive_queue *rq,
return err;
}
-static unsigned int get_mergeable_buf_len(struct ewma_pkt_len *avg_pkt_len)
+static unsigned int get_mergeable_buf_len(struct receive_queue *rq,
+ struct ewma_pkt_len *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_pkt_len_read(avg_pkt_len),
- GOOD_PACKET_LEN, PAGE_SIZE - hdr_len);
+ rq->min_buf_len - hdr_len, PAGE_SIZE - hdr_len);
return ALIGN(len, L1_CACHE_BYTES);
}
@@ -914,7 +919,7 @@ static int add_recvbuf_mergeable(struct virtnet_info *vi,
int err;
unsigned int len, hole;
- len = get_mergeable_buf_len(&rq->mrg_avg_pkt_len);
+ len = get_mergeable_buf_len(rq, &rq->mrg_avg_pkt_len);
if (unlikely(!skb_page_frag_refill(len + headroom, alloc_frag, gfp)))
return -ENOMEM;
@@ -2086,6 +2091,21 @@ static void virtnet_del_vqs(struct virtnet_info *vi)
virtnet_free_queues(vi);
}
+/* How large should a single buffer be so a queue full of these can fit at
+ * least one full packet?
+ * Logic below assumes the mergeable buffer header is used.
+ */
+static unsigned int mergeable_min_buf_len(struct virtnet_info *vi, struct
virtqueue *vq)
+{
+ const unsigned int hdr_len = sizeof(struct virtio_net_hdr_mrg_rxbuf);
+ unsigned int rq_size = virtqueue_get_vring_size(vq);
+ unsigned int packet_len = vi->big_packets ? IP_MAX_MTU :
vi->dev->max_mtu;
+ unsigned int buf_len = hdr_len + ETH_HLEN + VLAN_HLEN + packet_len;
+ unsigned int min_buf_len = DIV_ROUND_UP(buf_len, rq_size);
+
+ return max(min_buf_len, hdr_len);
+}
Consider rq_size may be large, I think this should be max(min_buf_len,
GOOD_PACKET_LEN)?
+
static int virtnet_find_vqs(struct virtnet_info *vi)
{
vq_callback_t **callbacks;
@@ -2151,6 +2171,7 @@ static int virtnet_find_vqs(struct virtnet_info *vi)
for (i = 0; i < vi->max_queue_pairs; i++) {
vi->rq[i].vq = vqs[rxq2vq(i)];
+ vi->rq[i].min_buf_len = mergeable_min_buf_len(vi, vi->rq[i].vq);
vi->sq[i].vq = vqs[txq2vq(i)];
}
@@ -2237,7 +2258,8 @@ static ssize_t mergeable_rx_buffer_size_show(struct netdev_rx_queue *queue,
BUG_ON(queue_index >= vi->max_queue_pairs);
avg = &vi->rq[queue_index].mrg_avg_pkt_len;
- return sprintf(buf, "%u\n", get_mergeable_buf_len(avg));
+ return sprintf(buf, "%u\n",
+ get_mergeable_buf_len(&vi->rq[queue_index], avg));
}
static struct rx_queue_attribute mergeable_rx_buffer_size_attribute =
[PATCH v2] virtio_net: fix support for small rings
When ring size is small (<32 entries) making buffers smaller means a
full ring might not be able to hold enough buffers to fit a single large
packet.
Make sure a ring full of buffers is large enough to allow at least one
packet of max size.
Fixes: 2613af0ed18a ("virtio_net: migrate mergeable rx buffers to page frag
allocators")
Signed-off-by: Michael S. Tsirkin
---
changes from v1:
typo fix
drivers/net/virtio_net.c | 30 ++
1 file changed, 26 insertions(+), 4 deletions(-)
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 9dc31dc..e5f6e34 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -29,6 +29,7 @@
#include
#include
#include
+#include
static int napi_weight = NAPI_POLL_WEIGHT;
module_param(napi_weight, int, 0444);
@@ -98,6 +99,9 @@ struct receive_queue {
/* RX: fragments + linear part + virtio header */
struct scatterlist sg[MAX_SKB_FRAGS + 2];
+ /* Min single buffer size for mergeable buffers case. */
+ unsigned int min_buf_len;
+
/* Name of this receive queue: input.$index */
char name[40];
};
@@ -894,13 +898,14 @@ static int add_recvbuf_big(struct virtnet_info *vi,
struct receive_queue *rq,
return err;
}
-static unsigned int get_mergeable_buf_len(struct ewma_pkt_len *avg_pkt_len)
+static unsigned int get_mergeable_buf_len(struct receive_queue *rq,
+ struct ewma_pkt_len *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_pkt_len_read(avg_pkt_len),
- GOOD_PACKET_LEN, PAGE_SIZE - hdr_len);
+ rq->min_buf_len - hdr_len, PAGE_SIZE - hdr_len);
return ALIGN(len, L1_CACHE_BYTES);
}
@@ -914,7 +919,7 @@ static int add_recvbuf_mergeable(struct virtnet_info *vi,
int err;
unsigned int len, hole;
- len = get_mergeable_buf_len(&rq->mrg_avg_pkt_len);
+ len = get_mergeable_buf_len(rq, &rq->mrg_avg_pkt_len);
if (unlikely(!skb_page_frag_refill(len + headroom, alloc_frag, gfp)))
return -ENOMEM;
@@ -2086,6 +2091,21 @@ static void virtnet_del_vqs(struct virtnet_info *vi)
virtnet_free_queues(vi);
}
+/* How large should a single buffer be so a queue full of these can fit at
+ * least one full packet?
+ * Logic below assumes the mergeable buffer header is used.
+ */
+static unsigned int mergeable_min_buf_len(struct virtnet_info *vi, struct
virtqueue *vq)
+{
+ const unsigned int hdr_len = sizeof(struct virtio_net_hdr_mrg_rxbuf);
+ unsigned int rq_size = virtqueue_get_vring_size(vq);
+ unsigned int packet_len = vi->big_packets ? IP_MAX_MTU :
vi->dev->max_mtu;
+ unsigned int buf_len = hdr_len + ETH_HLEN + VLAN_HLEN + packet_len;
+ unsigned int min_buf_len = DIV_ROUND_UP(buf_len, rq_size);
+
+ return max(min_buf_len, hdr_len);
+}
+
static int virtnet_find_vqs(struct virtnet_info *vi)
{
vq_callback_t **callbacks;
@@ -2151,6 +2171,7 @@ static int virtnet_find_vqs(struct virtnet_info *vi)
for (i = 0; i < vi->max_queue_pairs; i++) {
vi->rq[i].vq = vqs[rxq2vq(i)];
+ vi->rq[i].min_buf_len = mergeable_min_buf_len(vi, vi->rq[i].vq);
vi->sq[i].vq = vqs[txq2vq(i)];
}
@@ -2237,7 +2258,8 @@ static ssize_t mergeable_rx_buffer_size_show(struct
netdev_rx_queue *queue,
BUG_ON(queue_index >= vi->max_queue_pairs);
avg = &vi->rq[queue_index].mrg_avg_pkt_len;
- return sprintf(buf, "%u\n", get_mergeable_buf_len(avg));
+ return sprintf(buf, "%u\n",
+ get_mergeable_buf_len(&vi->rq[queue_index], avg));
}
static struct rx_queue_attribute mergeable_rx_buffer_size_attribute =
--
MST
