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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: 2613af0ed1 ("virtio_net: migrate mergeable rx buffers to page frag allocators")
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
This commit is contained in:
Michael S. Tsirkin 2017-03-09 02:21:21 +02:00
parent e377fcc848
commit d85b758f72
1 changed files with 26 additions and 4 deletions
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30
drivers/net/virtio_net.c
View File

@ -29,6 +29,7 @@
#include <linux/slab.h>
#include <linux/cpu.h>
#include <linux/average.h>
#include <net/route.h>
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];
};
@ -831,13 +835,14 @@ 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);
}
@ -851,7 +856,7 @@ 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;
@ -2023,6 +2028,21 @@ 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;
@ -2088,6 +2108,7 @@ 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)];
}
@ -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);
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 =