diff options
| -rw-r--r-- | include/linux/skbuff.h | 2 | ||||
| -rw-r--r-- | net/core/skbuff.c | 28 | ||||
| -rw-r--r-- | net/ipv4/udp.c | 12 |
3 files changed, 41 insertions, 1 deletions
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h index 9c535fbccf2c..0cd92b0f2af5 100644 --- a/include/linux/skbuff.h +++ b/include/linux/skbuff.h @@ -1966,6 +1966,8 @@ static inline int pskb_may_pull(struct sk_buff *skb, unsigned int len) return __pskb_pull_tail(skb, len - skb_headlen(skb)) != NULL; } +void skb_condense(struct sk_buff *skb); + /** * skb_headroom - bytes at buffer head * @skb: buffer to check diff --git a/net/core/skbuff.c b/net/core/skbuff.c index b45cd1494243..84151cf40aeb 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -4931,3 +4931,31 @@ struct sk_buff *pskb_extract(struct sk_buff *skb, int off, return clone; } EXPORT_SYMBOL(pskb_extract); + +/** + * skb_condense - try to get rid of fragments/frag_list if possible + * @skb: buffer + * + * Can be used to save memory before skb is added to a busy queue. + * If packet has bytes in frags and enough tail room in skb->head, + * pull all of them, so that we can free the frags right now and adjust + * truesize. + * Notes: + * We do not reallocate skb->head thus can not fail. + * Caller must re-evaluate skb->truesize if needed. + */ +void skb_condense(struct sk_buff *skb) +{ + if (!skb->data_len || + skb->data_len > skb->end - skb->tail || + skb_cloned(skb)) + return; + + /* Nice, we can free page frag(s) right now */ + __pskb_pull_tail(skb, skb->data_len); + + /* Now adjust skb->truesize, since __pskb_pull_tail() does + * not do this. + */ + skb->truesize = SKB_TRUESIZE(skb_end_offset(skb)); +} diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c index 16d88ba9ff1c..f5628ada47b5 100644 --- a/net/ipv4/udp.c +++ b/net/ipv4/udp.c @@ -1199,7 +1199,7 @@ int __udp_enqueue_schedule_skb(struct sock *sk, struct sk_buff *skb) { struct sk_buff_head *list = &sk->sk_receive_queue; int rmem, delta, amt, err = -ENOMEM; - int size = skb->truesize; + int size; /* try to avoid the costly atomic add/sub pair when the receive * queue is full; always allow at least a packet @@ -1208,6 +1208,16 @@ int __udp_enqueue_schedule_skb(struct sock *sk, struct sk_buff *skb) if (rmem > sk->sk_rcvbuf) goto drop; + /* Under mem pressure, it might be helpful to help udp_recvmsg() + * having linear skbs : + * - Reduce memory overhead and thus increase receive queue capacity + * - Less cache line misses at copyout() time + * - Less work at consume_skb() (less alien page frag freeing) + */ + if (rmem > (sk->sk_rcvbuf >> 1)) + skb_condense(skb); + size = skb->truesize; + /* we drop only if the receive buf is full and the receive * queue contains some other skb */ |