From e370a7236321773245c5522d8bb299380830d3b2 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Thu, 8 Aug 2013 14:37:32 -0700 Subject: af_unix: improve STREAM behavior with fragmented memory unix_stream_sendmsg() currently uses order-2 allocations, and we had numerous reports this can fail. The __GFP_REPEAT flag present in sock_alloc_send_pskb() is not helping. This patch extends the work done in commit eb6a24816b247c ("af_unix: reduce high order page allocations) for datagram sockets. This opens the possibility of zero copy IO (splice() and friends) The trick is to not use skb_pull() anymore in recvmsg() path, and instead add a @consumed field in UNIXCB() to track amount of already read payload in the skb. There is a performance regression for large sends because of extra page allocations that will be addressed in a follow-up patch, allowing sock_alloc_send_pskb() to attempt high order page allocations. Signed-off-by: Eric Dumazet Cc: David Rientjes Signed-off-by: David S. Miller --- net/unix/af_unix.c | 65 +++++++++++++++++++++++++----------------------------- 1 file changed, 30 insertions(+), 35 deletions(-) (limited to 'net/unix') diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c index c4ce243824bb..99dc760cdd95 100644 --- a/net/unix/af_unix.c +++ b/net/unix/af_unix.c @@ -1596,6 +1596,10 @@ out: return err; } +/* We use paged skbs for stream sockets, and limit occupancy to 32768 + * bytes, and a minimun of a full page. + */ +#define UNIX_SKB_FRAGS_SZ (PAGE_SIZE << get_order(32768)) static int unix_stream_sendmsg(struct kiocb *kiocb, struct socket *sock, struct msghdr *msg, size_t len) @@ -1609,6 +1613,7 @@ static int unix_stream_sendmsg(struct kiocb *kiocb, struct socket *sock, struct scm_cookie tmp_scm; bool fds_sent = false; int max_level; + int data_len; if (NULL == siocb->scm) siocb->scm = &tmp_scm; @@ -1635,40 +1640,21 @@ static int unix_stream_sendmsg(struct kiocb *kiocb, struct socket *sock, goto pipe_err; while (sent < len) { - /* - * Optimisation for the fact that under 0.01% of X - * messages typically need breaking up. - */ - - size = len-sent; + size = len - sent; /* Keep two messages in the pipe so it schedules better */ - if (size > ((sk->sk_sndbuf >> 1) - 64)) - size = (sk->sk_sndbuf >> 1) - 64; + size = min_t(int, size, (sk->sk_sndbuf >> 1) - 64); - if (size > SKB_MAX_ALLOC) - size = SKB_MAX_ALLOC; - - /* - * Grab a buffer - */ + /* allow fallback to order-0 allocations */ + size = min_t(int, size, SKB_MAX_HEAD(0) + UNIX_SKB_FRAGS_SZ); - skb = sock_alloc_send_skb(sk, size, msg->msg_flags&MSG_DONTWAIT, - &err); + data_len = max_t(int, 0, size - SKB_MAX_HEAD(0)); - if (skb == NULL) + skb = sock_alloc_send_pskb(sk, size - data_len, data_len, + msg->msg_flags & MSG_DONTWAIT, &err); + if (!skb) goto out_err; - /* - * If you pass two values to the sock_alloc_send_skb - * it tries to grab the large buffer with GFP_NOFS - * (which can fail easily), and if it fails grab the - * fallback size buffer which is under a page and will - * succeed. [Alan] - */ - size = min_t(int, size, skb_tailroom(skb)); - - /* Only send the fds in the first buffer */ err = unix_scm_to_skb(siocb->scm, skb, !fds_sent); if (err < 0) { @@ -1678,7 +1664,10 @@ static int unix_stream_sendmsg(struct kiocb *kiocb, struct socket *sock, max_level = err + 1; fds_sent = true; - err = memcpy_fromiovec(skb_put(skb, size), msg->msg_iov, size); + skb_put(skb, size - data_len); + skb->data_len = data_len; + skb->len = size; + err = skb_copy_datagram_from_iovec(skb, 0, msg->msg_iov, 0, size); if (err) { kfree_skb(skb); goto out_err; @@ -1890,6 +1879,11 @@ static long unix_stream_data_wait(struct sock *sk, long timeo, return timeo; } +static unsigned int unix_skb_len(const struct sk_buff *skb) +{ + return skb->len - UNIXCB(skb).consumed; +} + static int unix_stream_recvmsg(struct kiocb *iocb, struct socket *sock, struct msghdr *msg, size_t size, int flags) @@ -1977,8 +1971,8 @@ again: } skip = sk_peek_offset(sk, flags); - while (skip >= skb->len) { - skip -= skb->len; + while (skip >= unix_skb_len(skb)) { + skip -= unix_skb_len(skb); last = skb; skb = skb_peek_next(skb, &sk->sk_receive_queue); if (!skb) @@ -2005,8 +1999,9 @@ again: sunaddr = NULL; } - chunk = min_t(unsigned int, skb->len - skip, size); - if (memcpy_toiovec(msg->msg_iov, skb->data + skip, chunk)) { + chunk = min_t(unsigned int, unix_skb_len(skb) - skip, size); + if (skb_copy_datagram_iovec(skb, UNIXCB(skb).consumed + skip, + msg->msg_iov, chunk)) { if (copied == 0) copied = -EFAULT; break; @@ -2016,14 +2011,14 @@ again: /* Mark read part of skb as used */ if (!(flags & MSG_PEEK)) { - skb_pull(skb, chunk); + UNIXCB(skb).consumed += chunk; sk_peek_offset_bwd(sk, chunk); if (UNIXCB(skb).fp) unix_detach_fds(siocb->scm, skb); - if (skb->len) + if (unix_skb_len(skb)) break; skb_unlink(skb, &sk->sk_receive_queue); @@ -2107,7 +2102,7 @@ long unix_inq_len(struct sock *sk) if (sk->sk_type == SOCK_STREAM || sk->sk_type == SOCK_SEQPACKET) { skb_queue_walk(&sk->sk_receive_queue, skb) - amount += skb->len; + amount += unix_skb_len(skb); } else { skb = skb_peek(&sk->sk_receive_queue); if (skb) -- cgit v1.2.3-59-g8ed1b