net: use a per task frag allocator

We currently use a per socket order-0 page cache for tcp_sendmsg()
operations.

This page is used to build fragments for skbs.

Its done to increase probability of coalescing small write() into
single segments in skbs still in write queue (not yet sent)

But it wastes a lot of memory for applications handling many mostly
idle sockets, since each socket holds one page in sk->sk_sndmsg_page

Its also quite inefficient to build TSO 64KB packets, because we need
about 16 pages per skb on arches where PAGE_SIZE = 4096, so we hit
page allocator more than wanted.

This patch adds a per task frag allocator and uses bigger pages,
if available. An automatic fallback is done in case of memory pressure.

(up to 32768 bytes per frag, thats order-3 pages on x86)

This increases TCP stream performance by 20% on loopback device,
but also benefits on other network devices, since 8x less frags are
mapped on transmit and unmapped on tx completion. Alexander Duyck
mentioned a probable performance win on systems with IOMMU enabled.

Its possible some SG enabled hardware cant cope with bigger fragments,
but their ndo_start_xmit() should already handle this, splitting a
fragment in sub fragments, since some arches have PAGE_SIZE=65536

Successfully tested on various ethernet devices.
(ixgbe, igb, bnx2x, tg3, mellanox mlx4)

Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Ben Hutchings <bhutchings@solarflare.com>
Cc: Vijay Subramanian <subramanian.vijay@gmail.com>
Cc: Alexander Duyck <alexander.h.duyck@intel.com>
Tested-by: Vijay Subramanian <subramanian.vijay@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

4 files changed, 62 insertions, 114 deletions

diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
index a5beab1..24a29a3 100644
--- a/net/ipv4/ip_output.c
+++ b/net/ipv4/ip_output.c
@@ -793,6 +793,7 @@ static int __ip_append_data(struct sock *sk,
 			    struct flowi4 *fl4,
 			    struct sk_buff_head *queue,
 			    struct inet_cork *cork,
+			    struct page_frag *pfrag,
 			    int getfrag(void *from, char *to, int offset,
 					int len, int odd, struct sk_buff *skb),
 			    void *from, int length, int transhdrlen,
@@ -987,47 +988,30 @@ alloc_new_skb:
 			}
 		} else {
 			int i = skb_shinfo(skb)->nr_frags;
-			skb_frag_t *frag = &skb_shinfo(skb)->frags[i-1];
-			struct page *page = cork->page;
-			int off = cork->off;
-			unsigned int left;
-
-			if (page && (left = PAGE_SIZE - off) > 0) {
-				if (copy >= left)
-					copy = left;
-				if (page != skb_frag_page(frag)) {
-					if (i == MAX_SKB_FRAGS) {
-						err = -EMSGSIZE;
-						goto error;
-					}
-					skb_fill_page_desc(skb, i, page, off, 0);
-					skb_frag_ref(skb, i);
-					frag = &skb_shinfo(skb)->frags[i];
-				}
-			} else if (i < MAX_SKB_FRAGS) {
-				if (copy > PAGE_SIZE)
-					copy = PAGE_SIZE;
-				page = alloc_pages(sk->sk_allocation, 0);
-				if (page == NULL)  {
-					err = -ENOMEM;
-					goto error;
-				}
-				cork->page = page;
-				cork->off = 0;
 
-				skb_fill_page_desc(skb, i, page, 0, 0);
-				frag = &skb_shinfo(skb)->frags[i];
-			} else {
-				err = -EMSGSIZE;
-				goto error;
-			}
-			if (getfrag(from, skb_frag_address(frag)+skb_frag_size(frag),
-				    offset, copy, skb->len, skb) < 0) {
-				err = -EFAULT;
+			err = -ENOMEM;
+			if (!sk_page_frag_refill(sk, pfrag))
 				goto error;
+
+			if (!skb_can_coalesce(skb, i, pfrag->page,
+					      pfrag->offset)) {
+				err = -EMSGSIZE;
+				if (i == MAX_SKB_FRAGS)
+					goto error;
+
+				__skb_fill_page_desc(skb, i, pfrag->page,
+						     pfrag->offset, 0);
+				skb_shinfo(skb)->nr_frags = ++i;
+				get_page(pfrag->page);
 			}
-			cork->off += copy;
-			skb_frag_size_add(frag, copy);
+			copy = min_t(int, copy, pfrag->size - pfrag->offset);
+			if (getfrag(from,
+				    page_address(pfrag->page) + pfrag->offset,
+				    offset, copy, skb->len, skb) < 0)
+				goto error_efault;
+
+			pfrag->offset += copy;
+			skb_frag_size_add(&skb_shinfo(skb)->frags[i - 1], copy);
 			skb->len += copy;
 			skb->data_len += copy;
 			skb->truesize += copy;
@@ -1039,6 +1023,8 @@ alloc_new_skb:
 
 	return 0;
 
+error_efault:
+	err = -EFAULT;
 error:
 	cork->length -= length;
 	IP_INC_STATS(sock_net(sk), IPSTATS_MIB_OUTDISCARDS);
@@ -1079,8 +1065,6 @@ static int ip_setup_cork(struct sock *sk, struct inet_cork *cork,
 	cork->dst = &rt->dst;
 	cork->length = 0;
 	cork->tx_flags = ipc->tx_flags;
-	cork->page = NULL;
-	cork->off = 0;
 
 	return 0;
 }
@@ -1117,7 +1101,8 @@ int ip_append_data(struct sock *sk, struct flowi4 *fl4,
 		transhdrlen = 0;
 	}
 
-	return __ip_append_data(sk, fl4, &sk->sk_write_queue, &inet->cork.base, getfrag,
+	return __ip_append_data(sk, fl4, &sk->sk_write_queue, &inet->cork.base,
+				sk_page_frag(sk), getfrag,
 				from, length, transhdrlen, flags);
 }
 
@@ -1439,7 +1424,8 @@ struct sk_buff *ip_make_skb(struct sock *sk,
 	if (err)
 		return ERR_PTR(err);
 
-	err = __ip_append_data(sk, fl4, &queue, &cork, getfrag,
+	err = __ip_append_data(sk, fl4, &queue, &cork,
+			       &current->task_frag, getfrag,
 			       from, length, transhdrlen, flags);
 	if (err) {
 		__ip_flush_pending_frames(sk, &queue, &cork);
diff --git a/net/ipv4/raw.c b/net/ipv4/raw.c
index f242578..a80740b 100644
--- a/net/ipv4/raw.c
+++ b/net/ipv4/raw.c
@@ -131,18 +131,23 @@ found:
  *	0 - deliver
  *	1 - block
  */
-static __inline__ int icmp_filter(struct sock *sk, struct sk_buff *skb)
+static int icmp_filter(const struct sock *sk, const struct sk_buff *skb)
 {
-	int type;
-
-	if (!pskb_may_pull(skb, sizeof(struct icmphdr)))
+	struct icmphdr _hdr;
+	const struct icmphdr *hdr;
+
+	pr_err("icmp_filter skb_transport_offset %d data-head %ld len %d/%d\n",
+		skb_transport_offset(skb), skb->data - skb->head, skb->len, skb->data_len);
+	hdr = skb_header_pointer(skb, skb_transport_offset(skb),
+				 sizeof(_hdr), &_hdr);
+	pr_err("head %p data %p hdr %p type %d\n", skb->head, skb->data, hdr, hdr ? hdr->type : -1);
+	if (!hdr)
 		return 1;
 
-	type = icmp_hdr(skb)->type;
-	if (type < 32) {
+	if (hdr->type < 32) {
 		__u32 data = raw_sk(sk)->filter.data;
 
-		return ((1 << type) & data) != 0;
+		return ((1U << hdr->type) & data) != 0;
 	}
 
 	/* Do not block unknown ICMP types */
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 7b1e940..72ea475 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -1150,78 +1150,43 @@ new_segment:
 				if (err)
 					goto do_fault;
 			} else {
-				bool merge = false;
+				bool merge = true;
 				int i = skb_shinfo(skb)->nr_frags;
-				struct page *page = sk->sk_sndmsg_page;
-				int off;
-
-				if (page && page_count(page) == 1)
-					sk->sk_sndmsg_off = 0;
-
-				off = sk->sk_sndmsg_off;
-
-				if (skb_can_coalesce(skb, i, page, off) &&
-				    off != PAGE_SIZE) {
-					/* We can extend the last page
-					 * fragment. */
-					merge = true;
-				} else if (i == MAX_SKB_FRAGS || !sg) {
-					/* Need to add new fragment and cannot
-					 * do this because interface is non-SG,
-					 * or because all the page slots are
-					 * busy. */
-					tcp_mark_push(tp, skb);
-					goto new_segment;
-				} else if (page) {
-					if (off == PAGE_SIZE) {
-						put_page(page);
-						sk->sk_sndmsg_page = page = NULL;
-						off = 0;
+				struct page_frag *pfrag = sk_page_frag(sk);
+
+				if (!sk_page_frag_refill(sk, pfrag))
+					goto wait_for_memory;
+
+				if (!skb_can_coalesce(skb, i, pfrag->page,
+						      pfrag->offset)) {
+					if (i == MAX_SKB_FRAGS || !sg) {
+						tcp_mark_push(tp, skb);
+						goto new_segment;
 					}
-				} else
-					off = 0;
+					merge = false;
+				}
 
-				if (copy > PAGE_SIZE - off)
-					copy = PAGE_SIZE - off;
+				copy = min_t(int, copy, pfrag->size - pfrag->offset);
 
 				if (!sk_wmem_schedule(sk, copy))
 					goto wait_for_memory;
 
-				if (!page) {
-					/* Allocate new cache page. */
-					if (!(page = sk_stream_alloc_page(sk)))
-						goto wait_for_memory;
-				}
-
-				/* Time to copy data. We are close to
-				 * the end! */
 				err = skb_copy_to_page_nocache(sk, from, skb,
-							       page, off, copy);
-				if (err) {
-					/* If this page was new, give it to the
-					 * socket so it does not get leaked.
-					 */
-					if (!sk->sk_sndmsg_page) {
-						sk->sk_sndmsg_page = page;
-						sk->sk_sndmsg_off = 0;
-					}
+							       pfrag->page,
+							       pfrag->offset,
+							       copy);
+				if (err)
 					goto do_error;
-				}
 
 				/* Update the skb. */
 				if (merge) {
 					skb_frag_size_add(&skb_shinfo(skb)->frags[i - 1], copy);
 				} else {
-					skb_fill_page_desc(skb, i, page, off, copy);
-					if (sk->sk_sndmsg_page) {
-						get_page(page);
-					} else if (off + copy < PAGE_SIZE) {
-						get_page(page);
-						sk->sk_sndmsg_page = page;
-					}
+					skb_fill_page_desc(skb, i, pfrag->page,
+							   pfrag->offset, copy);
+					get_page(pfrag->page);
 				}
-
-				sk->sk_sndmsg_off = off + copy;
+				pfrag->offset += copy;
 			}
 
 			if (!copied)
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 0a7e020..93406c5 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -2200,14 +2200,6 @@ void tcp_v4_destroy_sock(struct sock *sk)
 	if (inet_csk(sk)->icsk_bind_hash)
 		inet_put_port(sk);
 
-	/*
-	 * If sendmsg cached page exists, toss it.
-	 */
-	if (sk->sk_sndmsg_page) {
-		__free_page(sk->sk_sndmsg_page);
-		sk->sk_sndmsg_page = NULL;
-	}
-
 	/* TCP Cookie Transactions */
 	if (tp->cookie_values != NULL) {
 		kref_put(&tp->cookie_values->kref,