diff options
Diffstat (limited to 'net/vmw_vsock/virtio_transport_common.c')
| -rw-r--r-- | net/vmw_vsock/virtio_transport_common.c | 165 |
1 files changed, 164 insertions, 1 deletions
diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c index 09475007165b..8becad81279c 100644 --- a/net/vmw_vsock/virtio_transport_common.c +++ b/net/vmw_vsock/virtio_transport_common.c @@ -26,6 +26,13 @@ /* Threshold for detecting small packets to copy */ #define GOOD_COPY_LEN 128 +/* Max payload that can be collapsed into a single linear skb, using the same + * allocation threshold as virtio_vsock_alloc_skb() to avoid adding pressure + * on the page allocator. + */ +#define MAX_COLLAPSE_LEN \ + SKB_MAX_ORDER(VIRTIO_VSOCK_SKB_HEADROOM, PAGE_ALLOC_COSTLY_ORDER) + static void virtio_transport_cancel_close_work(struct vsock_sock *vsk, bool cancel_timeout); static s64 virtio_transport_has_space(struct virtio_vsock_sock *vvs); @@ -420,6 +427,145 @@ static int virtio_transport_send_pkt_info(struct vsock_sock *vsk, return ret; } +static bool virtio_transport_can_collapse(struct sk_buff *skb) +{ + /* skbs that are partially consumed, mark a SEQPACKET message boundary, + * or are already large enough should not be collapsed: they either + * need special accounting, carry protocol state, or already have a + * good data-to-overhead ratio. + */ + if (VIRTIO_VSOCK_SKB_CB(skb)->offset) + return false; + if (le32_to_cpu(virtio_vsock_hdr(skb)->flags) & VIRTIO_VSOCK_SEQ_EOM) + return false; + if (skb->len >= MAX_COLLAPSE_LEN) + return false; + return true; +} + +/* Iterate through the packets in the queue starting from the current skb to + * count the number of bytes we can collapse. + */ +static unsigned int +virtio_transport_collapse_size(struct sk_buff *skb, struct sk_buff_head *queue) +{ + unsigned int target = skb->len - VIRTIO_VSOCK_SKB_CB(skb)->offset; + + while ((skb = skb_peek_next(skb, queue)) && + virtio_transport_can_collapse(skb)) { + unsigned int len = skb->len - VIRTIO_VSOCK_SKB_CB(skb)->offset; + + if (len > MAX_COLLAPSE_LEN - target) + return target; + + target += len; + } + + return target; +} + +/* Called under lock_sock to compact the receive queue by merging small skbs. + * @min_to_free: minimum number of skbs to eliminate from the queue. May free + * more to fill each collapsed skb to capacity. + */ +static void +virtio_transport_collapse_rx_queue(struct virtio_vsock_sock *vvs, + u32 min_to_free) +{ + struct sk_buff *skb, *next_skb, *new_skb = NULL; + struct sk_buff_head new_queue; + u32 saved = 0; + + __skb_queue_head_init(&new_queue); + + skb_queue_walk_safe(&vvs->rx_queue, skb, next_skb) { + struct virtio_vsock_hdr *hdr = virtio_vsock_hdr(skb); + u32 src_off = VIRTIO_VSOCK_SKB_CB(skb)->offset; + u32 src_len = skb->len - src_off; + bool keep; + + keep = !virtio_transport_can_collapse(skb); + if (keep) { + /* Finalize pending collapsed skb to preserve packet + * ordering. + */ + if (new_skb) { + __skb_queue_tail(&new_queue, new_skb); + new_skb = NULL; + saved--; + } + goto next; + } + + /* Finalize if this packet won't fit in the remaining tailroom, + * so we can allocate a right-sized new_skb. + */ + if (new_skb && src_len > skb_tailroom(new_skb)) { + __skb_queue_tail(&new_queue, new_skb); + new_skb = NULL; + saved--; + } + + if (!new_skb) { + unsigned int alloc_size; + + /* Check after finalizing to opportunistically fill + * each collapsed skb to capacity, merging more skbs + * than strictly required. + */ + if (saved >= min_to_free) + break; + + alloc_size = virtio_transport_collapse_size(skb, &vvs->rx_queue); + + /* Only this skb's data is eligible, nothing to merge + * with. Keep as-is. + */ + if (alloc_size <= src_len) { + keep = true; + goto next; + } + + new_skb = virtio_vsock_alloc_linear_skb(alloc_size + + VIRTIO_VSOCK_SKB_HEADROOM, GFP_KERNEL); + if (!new_skb) + break; + + memcpy(virtio_vsock_hdr(new_skb), hdr, + sizeof(struct virtio_vsock_hdr)); + virtio_vsock_hdr(new_skb)->len = 0; + } + + /* Cannot fail since src_off/src_len are within bounds, but if + * it does, discard new_skb to avoid queuing corrupted data. + */ + if (WARN_ON_ONCE(skb_copy_bits(skb, src_off, + skb_put(new_skb, src_len), + src_len))) { + kfree_skb(new_skb); + new_skb = NULL; + break; + } + + le32_add_cpu(&virtio_vsock_hdr(new_skb)->len, src_len); + virtio_vsock_hdr(new_skb)->flags |= hdr->flags; + +next: + __skb_unlink(skb, &vvs->rx_queue); + if (keep) { + __skb_queue_tail(&new_queue, skb); + } else { + consume_skb(skb); + saved++; + } + } + + if (new_skb) + __skb_queue_tail(&new_queue, new_skb); + + skb_queue_splice(&new_queue, &vvs->rx_queue); +} + static bool virtio_transport_inc_rx_pkt(struct virtio_vsock_sock *vvs, u32 len) { @@ -1354,12 +1500,29 @@ virtio_transport_recv_enqueue(struct vsock_sock *vsk, { struct virtio_vsock_sock *vvs = vsk->trans; bool can_enqueue, free_pkt = false; + u32 len, queue_max, queue_len; struct virtio_vsock_hdr *hdr; - u32 len; hdr = virtio_vsock_hdr(skb); len = le32_to_cpu(hdr->len); + /* virtio_transport_inc_rx_pkt() rejects packets when the per-skb + * overhead (skb_queue_len * SKB_TRUESIZE(0)) exceeds buf_alloc. + * Proactively collapse the queue before that happens. + * No rx_lock needed: lock_sock is held by caller, preventing + * concurrent enqueue or dequeue. + */ + queue_max = vvs->buf_alloc / SKB_TRUESIZE(0); + queue_len = skb_queue_len(&vvs->rx_queue); + if (queue_len >= queue_max) { + /* Walking a large queue may take a significant amount of time + * and cache misses, causing traffic burstiness. Limit the + * collapse to freeing room for this packet and the next one. + * It may free more to fill each collapsed skb to capacity. + */ + virtio_transport_collapse_rx_queue(vvs, queue_len + 2 - queue_max); + } + spin_lock_bh(&vvs->rx_lock); can_enqueue = virtio_transport_inc_rx_pkt(vvs, len); |