diff options
-rw-r--r-- | net/ipv4/udp.c | 114 |
1 files changed, 103 insertions, 11 deletions
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c index d8b265f1a33b..2bc638c48b86 100644 --- a/net/ipv4/udp.c +++ b/net/ipv4/udp.c @@ -1163,6 +1163,83 @@ out: return ret; } +/* Copy as much information as possible into skb->dev_scratch to avoid + * possibly multiple cache miss on dequeue(); + */ +#if BITS_PER_LONG == 64 + +/* we can store multiple info here: truesize, len and the bit needed to + * compute skb_csum_unnecessary will be on cold cache lines at recvmsg + * time. + * skb->len can be stored on 16 bits since the udp header has been already + * validated and pulled. + */ +struct udp_dev_scratch { + u32 truesize; + u16 len; + bool is_linear; + bool csum_unnecessary; +}; + +static void udp_set_dev_scratch(struct sk_buff *skb) +{ + struct udp_dev_scratch *scratch; + + BUILD_BUG_ON(sizeof(struct udp_dev_scratch) > sizeof(long)); + scratch = (struct udp_dev_scratch *)&skb->dev_scratch; + scratch->truesize = skb->truesize; + scratch->len = skb->len; + scratch->csum_unnecessary = !!skb_csum_unnecessary(skb); + scratch->is_linear = !skb_is_nonlinear(skb); +} + +static int udp_skb_truesize(struct sk_buff *skb) +{ + return ((struct udp_dev_scratch *)&skb->dev_scratch)->truesize; +} + +static unsigned int udp_skb_len(struct sk_buff *skb) +{ + return ((struct udp_dev_scratch *)&skb->dev_scratch)->len; +} + +static bool udp_skb_csum_unnecessary(struct sk_buff *skb) +{ + return ((struct udp_dev_scratch *)&skb->dev_scratch)->csum_unnecessary; +} + +static bool udp_skb_is_linear(struct sk_buff *skb) +{ + return ((struct udp_dev_scratch *)&skb->dev_scratch)->is_linear; +} + +#else +static void udp_set_dev_scratch(struct sk_buff *skb) +{ + skb->dev_scratch = skb->truesize; +} + +static int udp_skb_truesize(struct sk_buff *skb) +{ + return skb->dev_scratch; +} + +static unsigned int udp_skb_len(struct sk_buff *skb) +{ + return skb->len; +} + +static bool udp_skb_csum_unnecessary(struct sk_buff *skb) +{ + return skb_csum_unnecessary(skb); +} + +static bool udp_skb_is_linear(struct sk_buff *skb) +{ + return !skb_is_nonlinear(skb); +} +#endif + /* fully reclaim rmem/fwd memory allocated for skb */ static void udp_rmem_release(struct sock *sk, int size, int partial, bool rx_queue_lock_held) @@ -1213,14 +1290,16 @@ static void udp_rmem_release(struct sock *sk, int size, int partial, */ void udp_skb_destructor(struct sock *sk, struct sk_buff *skb) { - udp_rmem_release(sk, skb->dev_scratch, 1, false); + prefetch(&skb->data); + udp_rmem_release(sk, udp_skb_truesize(skb), 1, false); } EXPORT_SYMBOL(udp_skb_destructor); /* as above, but the caller held the rx queue lock, too */ static void udp_skb_dtor_locked(struct sock *sk, struct sk_buff *skb) { - udp_rmem_release(sk, skb->dev_scratch, 1, true); + prefetch(&skb->data); + udp_rmem_release(sk, udp_skb_truesize(skb), 1, true); } /* Idea of busylocks is to let producers grab an extra spinlock @@ -1274,10 +1353,7 @@ int __udp_enqueue_schedule_skb(struct sock *sk, struct sk_buff *skb) busy = busylock_acquire(sk); } size = skb->truesize; - /* Copy skb->truesize into skb->dev_scratch to avoid a cache line miss - * in udp_skb_destructor() - */ - skb->dev_scratch = size; + udp_set_dev_scratch(skb); /* we drop only if the receive buf is full and the receive * queue contains some other skb @@ -1515,6 +1591,18 @@ busy_check: } EXPORT_SYMBOL_GPL(__skb_recv_udp); +static int copy_linear_skb(struct sk_buff *skb, int len, int off, + struct iov_iter *to) +{ + int n, copy = len - off; + + n = copy_to_iter(skb->data + off, copy, to); + if (n == copy) + return 0; + + return -EFAULT; +} + /* * This should be easy, if there is something there we * return it, otherwise we block. @@ -1541,7 +1629,7 @@ try_again: if (!skb) return err; - ulen = skb->len; + ulen = udp_skb_len(skb); copied = len; if (copied > ulen - off) copied = ulen - off; @@ -1556,14 +1644,18 @@ try_again: if (copied < ulen || peeking || (is_udplite && UDP_SKB_CB(skb)->partial_cov)) { - checksum_valid = !udp_lib_checksum_complete(skb); + checksum_valid = udp_skb_csum_unnecessary(skb) || + !__udp_lib_checksum_complete(skb); if (!checksum_valid) goto csum_copy_err; } - if (checksum_valid || skb_csum_unnecessary(skb)) - err = skb_copy_datagram_msg(skb, off, msg, copied); - else { + if (checksum_valid || udp_skb_csum_unnecessary(skb)) { + if (udp_skb_is_linear(skb)) + err = copy_linear_skb(skb, copied, off, &msg->msg_iter); + else + err = skb_copy_datagram_msg(skb, off, msg, copied); + } else { err = skb_copy_and_csum_datagram_msg(skb, off, msg); if (err == -EINVAL) |