Commit d85b758f authored by Michael S. Tsirkin's avatar Michael S. Tsirkin

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: 2613af0e ("virtio_net: migrate mergeable rx buffers to page frag allocators")
Signed-off-by: default avatarMichael S. Tsirkin <mst@redhat.com>
parent e377fcc8
...@@ -29,6 +29,7 @@ ...@@ -29,6 +29,7 @@
#include <linux/slab.h> #include <linux/slab.h>
#include <linux/cpu.h> #include <linux/cpu.h>
#include <linux/average.h> #include <linux/average.h>
#include <net/route.h>
static int napi_weight = NAPI_POLL_WEIGHT; static int napi_weight = NAPI_POLL_WEIGHT;
module_param(napi_weight, int, 0444); module_param(napi_weight, int, 0444);
...@@ -98,6 +99,9 @@ struct receive_queue { ...@@ -98,6 +99,9 @@ struct receive_queue {
/* RX: fragments + linear part + virtio header */ /* RX: fragments + linear part + virtio header */
struct scatterlist sg[MAX_SKB_FRAGS + 2]; 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.$index */ /* Name of this receive queue: input.$index */
char name[40]; char name[40];
}; };
...@@ -831,13 +835,14 @@ static int add_recvbuf_big(struct virtnet_info *vi, struct receive_queue *rq, ...@@ -831,13 +835,14 @@ static int add_recvbuf_big(struct virtnet_info *vi, struct receive_queue *rq,
return err; 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); const size_t hdr_len = sizeof(struct virtio_net_hdr_mrg_rxbuf);
unsigned int len; unsigned int len;
len = hdr_len + clamp_t(unsigned int, ewma_pkt_len_read(avg_pkt_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); return ALIGN(len, L1_CACHE_BYTES);
} }
...@@ -851,7 +856,7 @@ static int add_recvbuf_mergeable(struct virtnet_info *vi, ...@@ -851,7 +856,7 @@ static int add_recvbuf_mergeable(struct virtnet_info *vi,
int err; int err;
unsigned int len, hole; 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))) if (unlikely(!skb_page_frag_refill(len + headroom, alloc_frag, gfp)))
return -ENOMEM; return -ENOMEM;
...@@ -2023,6 +2028,21 @@ static void virtnet_del_vqs(struct virtnet_info *vi) ...@@ -2023,6 +2028,21 @@ static void virtnet_del_vqs(struct virtnet_info *vi)
virtnet_free_queues(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) static int virtnet_find_vqs(struct virtnet_info *vi)
{ {
vq_callback_t **callbacks; vq_callback_t **callbacks;
...@@ -2088,6 +2108,7 @@ static int virtnet_find_vqs(struct virtnet_info *vi) ...@@ -2088,6 +2108,7 @@ static int virtnet_find_vqs(struct virtnet_info *vi)
for (i = 0; i < vi->max_queue_pairs; i++) { for (i = 0; i < vi->max_queue_pairs; i++) {
vi->rq[i].vq = vqs[rxq2vq(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)]; vi->sq[i].vq = vqs[txq2vq(i)];
} }
...@@ -2174,7 +2195,8 @@ static ssize_t mergeable_rx_buffer_size_show(struct netdev_rx_queue *queue, ...@@ -2174,7 +2195,8 @@ static ssize_t mergeable_rx_buffer_size_show(struct netdev_rx_queue *queue,
BUG_ON(queue_index >= vi->max_queue_pairs); BUG_ON(queue_index >= vi->max_queue_pairs);
avg = &vi->rq[queue_index].mrg_avg_pkt_len; 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 = static struct rx_queue_attribute mergeable_rx_buffer_size_attribute =
......
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