The virtio-net driver currently uses netdev_alloc_frag() for GFP_ATOMIC
mergeable rx buffer allocations. This commit migrates virtio-net to use
per-receive queue page frags for GFP_ATOMIC allocation. This change unifies
mergeable rx buffer memory allocation, which now will use skb_refill_frag()
for both atomic and GFP-WAIT buffer allocations.
To address fragmentation concerns, if after buffer allocation there
is too little space left in the page frag to allocate a subsequent
buffer, the remaining space is added to the current allocated buffer
so that the remaining space can be used to store packet data.
Signed-off-by: Michael Dalton <mwdalton@xxxxxxxxxx>
---
v2->v3: Unchanged
v1->v2: Use GFP_COLD for RX buffer allocations (as in netdev_alloc_frag()).
Remove per-netdev GFP_KERNEL page_frag allocator.
drivers/net/virtio_net.c | 69 ++++++++++++++++++++++++------------------------
1 file changed, 35 insertions(+), 34 deletions(-)
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 7b17240..36cbf06 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -78,6 +78,9 @@ struct receive_queue {
/* Chain pages by the private ptr. */
struct page *pages;
+ /* Page frag for packet buffer allocation. */
+ struct page_frag alloc_frag;
+
/* RX: fragments + linear part + virtio header */
struct scatterlist sg[MAX_SKB_FRAGS + 2];
@@ -126,11 +129,6 @@ struct virtnet_info {
/* Lock for config space updates */
struct mutex config_lock;
- /* Page_frag for GFP_KERNEL packet buffer allocation when we run
- * low on memory.
- */
- struct page_frag alloc_frag;
-
/* Does the affinity hint is set for virtqueues? */
bool affinity_hint_set;
@@ -336,8 +334,8 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
int num_buf = hdr->mhdr.num_buffers;
struct page *page = virt_to_head_page(buf);
int offset = buf - page_address(page);
- struct sk_buff *head_skb = page_to_skb(rq, page, offset, len,
- MERGE_BUFFER_LEN);
+ unsigned int truesize = max_t(unsigned int, len, MERGE_BUFFER_LEN);
+ struct sk_buff *head_skb = page_to_skb(rq, page, offset, len, truesize);
struct sk_buff *curr_skb = head_skb;
if (unlikely(!curr_skb))
@@ -353,11 +351,6 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
dev->stats.rx_length_errors++;
goto err_buf;
}
- if (unlikely(len > MERGE_BUFFER_LEN)) {
- pr_debug("%s: rx error: merge buffer too long\n",
- dev->name);
- len = MERGE_BUFFER_LEN;
- }
page = virt_to_head_page(buf);
--rq->num;
@@ -376,19 +369,20 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
head_skb->truesize += nskb->truesize;
num_skb_frags = 0;
}
+ truesize = max_t(unsigned int, len, MERGE_BUFFER_LEN);
if (curr_skb != head_skb) {
head_skb->data_len += len;
head_skb->len += len;
- head_skb->truesize += MERGE_BUFFER_LEN;
+ head_skb->truesize += truesize;
}
offset = buf - page_address(page);
if (skb_can_coalesce(curr_skb, num_skb_frags, page, offset)) {
put_page(page);
skb_coalesce_rx_frag(curr_skb, num_skb_frags - 1,
- len, MERGE_BUFFER_LEN);
+ len, truesize);
} else {
skb_add_rx_frag(curr_skb, num_skb_frags, page,
- offset, len, MERGE_BUFFER_LEN);
+ offset, len, truesize);
}
}
@@ -578,25 +572,24 @@ static int add_recvbuf_big(struct receive_queue *rq, gfp_t gfp)
static int add_recvbuf_mergeable(struct receive_queue *rq, gfp_t gfp)
{
- struct virtnet_info *vi = rq->vq->vdev->priv;
- char *buf = NULL;
+ struct page_frag *alloc_frag = &rq->alloc_frag;
+ char *buf;
int err;
+ unsigned int len, hole;
- if (gfp & __GFP_WAIT) {
- if (skb_page_frag_refill(MERGE_BUFFER_LEN, &vi->alloc_frag,
- gfp)) {
- buf = (char *)page_address(vi->alloc_frag.page) +
- vi->alloc_frag.offset;
- get_page(vi->alloc_frag.page);
- vi->alloc_frag.offset += MERGE_BUFFER_LEN;
- }
- } else {
- buf = netdev_alloc_frag(MERGE_BUFFER_LEN);
- }
- if (!buf)
+ if (unlikely(!skb_page_frag_refill(MERGE_BUFFER_LEN, alloc_frag, gfp)))
return -ENOMEM;
+ buf = (char *)page_address(alloc_frag->page) + alloc_frag->offset;
+ get_page(alloc_frag->page);
+ len = MERGE_BUFFER_LEN;
+ alloc_frag->offset += len;
+ hole = alloc_frag->size - alloc_frag->offset;
+ if (hole < MERGE_BUFFER_LEN) {
+ len += hole;
+ alloc_frag->offset += hole;
+ }
- sg_init_one(rq->sg, buf, MERGE_BUFFER_LEN);
+ sg_init_one(rq->sg, buf, len);
err = virtqueue_add_inbuf(rq->vq, rq->sg, 1, buf, gfp);
if (err < 0)
put_page(virt_to_head_page(buf));
@@ -617,6 +610,7 @@ static bool try_fill_recv(struct receive_queue *rq, gfp_t gfp)
int err;
bool oom;
+ gfp |= __GFP_COLD;
do {
if (vi->mergeable_rx_bufs)
err = add_recvbuf_mergeable(rq, gfp);
@@ -1377,6 +1371,14 @@ static void free_receive_bufs(struct virtnet_info *vi)
}
}
+static void free_receive_page_frags(struct virtnet_info *vi)
+{
+ int i;
+ for (i = 0; i < vi->max_queue_pairs; i++)
+ if (vi->rq[i].alloc_frag.page)
+ put_page(vi->rq[i].alloc_frag.page);
+}
+
static void free_unused_bufs(struct virtnet_info *vi)
{
void *buf;
@@ -1705,9 +1707,8 @@ free_recv_bufs:
unregister_netdev(dev);
free_vqs:
cancel_delayed_work_sync(&vi->refill);
+ free_receive_page_frags(vi);
virtnet_del_vqs(vi);
- if (vi->alloc_frag.page)
- put_page(vi->alloc_frag.page);
free_stats:
free_percpu(vi->stats);
free:
@@ -1724,6 +1725,8 @@ static void remove_vq_common(struct virtnet_info *vi)
free_receive_bufs(vi);
+ free_receive_page_frags(vi);
+
virtnet_del_vqs(vi);
}
@@ -1741,8 +1744,6 @@ static void virtnet_remove(struct virtio_device *vdev)
unregister_netdev(vi->dev);
remove_vq_common(vi);
- if (vi->alloc_frag.page)
- put_page(vi->alloc_frag.page);
flush_work(&vi->config_work);
--
1.8.5.2
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