On Tue, Jan 20, 2009 at 08:37:26AM +0000, Jarek Poplawski wrote:

...

quoted text
> Here is a tiny upgrade to save some memory by reusing a page for more

> chunks if possible, which I think could be considered, after the

> testing of the main patch is finished. (There could be also added an

> additional freeing of this cached page before socket destruction,

> maybe in tcp_splice_read(), if somebody finds good place.)

OOPS! I did it again... Here is better refcounting.
Jarek P.
--- (take 2)
 include/net/sock.h  |    4 ++++

 net/core/skbuff.c   |   32 ++++++++++++++++++++++++++------

 net/core/sock.c     |    2 ++

 net/ipv4/tcp_ipv4.c |    8 ++++++++

 4 files changed, 40 insertions(+), 6 deletions(-)
diff --git a/include/net/sock.h b/include/net/sock.h

index 5a3a151..4ded741 100644

--- a/include/net/sock.h

+++ b/include/net/sock.h

@@ -190,6 +190,8 @@ struct sock_common {

   *	@sk_user_data: RPC layer private data

   *	@sk_sndmsg_page: cached page for sendmsg

   *	@sk_sndmsg_off: cached offset for sendmsg

+  *	@sk_splice_page: cached page for splice

+  *	@sk_splice_off: cached offset for splice

   *	@sk_send_head: front of stuff to transmit

   *	@sk_security: used by security modules

   *	@sk_mark: generic packet mark

@@ -279,6 +281,8 @@ struct sock {

 	struct page		*sk_sndmsg_page;

 	struct sk_buff		*sk_send_head;

 	__u32			sk_sndmsg_off;

+	struct page		*sk_splice_page;

+	__u32			sk_splice_off;

 	int			sk_write_pending;

 #ifdef CONFIG_SECURITY

 	void			*sk_security;

diff --git a/net/core/skbuff.c b/net/core/skbuff.c

index 56272ac..02a1a6c 100644

--- a/net/core/skbuff.c

+++ b/net/core/skbuff.c

@@ -1334,13 +1334,33 @@ static void sock_spd_release(struct splice_pipe_desc *spd, unsigned int i)

 }
 static inline struct page *linear_to_page(struct page *page, unsigned int len,

-					  unsigned int offset)

+					  unsigned int *offset,

+					  struct sk_buff *skb)

 {

-	struct page *p = alloc_pages(GFP_KERNEL, 0);

+	struct sock *sk = skb->sk;

+	struct page *p = sk->sk_splice_page;

+	unsigned int off;
-	if (!p)

-		return NULL;

-	memcpy(page_address(p) + offset, page_address(page) + offset, len);

+	if (!p) {

+new_page:

+		p = sk->sk_splice_page = alloc_pages(sk->sk_allocation, 0);

+		if (!p)

+			return NULL;

+

+		off = sk->sk_splice_off = 0;

+		/* we hold one ref to this page until it's full or unneeded */

+	} else {

+		off = sk->sk_splice_off;

+		if (off + len > PAGE_SIZE) {

+			put_page(p);

+			goto new_page;

+		}

+	}

+

+	memcpy(page_address(p) + off, page_address(page) + *offset, len);

+	sk->sk_splice_off += len;

+	*offset = off;

+	get_page(p);
 	return p;

 }

@@ -1356,7 +1376,7 @@ static inline int spd_fill_page(struct splice_pipe_desc *spd, struct page *page,

 		return 1;
 	if (linear) {

-		page = linear_to_page(page, len, offset);

+		page = linear_to_page(page, len, &offset, skb);

 		if (!page)

 			return 1;

 	} else

diff --git a/net/core/sock.c b/net/core/sock.c

index f3a0d08..6b258a9 100644

--- a/net/core/sock.c

+++ b/net/core/sock.c

@@ -1732,6 +1732,8 @@ void sock_init_data(struct socket *sock, struct sock *sk)
 	sk->sk_sndmsg_page	=	NULL;

 	sk->sk_sndmsg_off	=	0;

+	sk->sk_splice_page	=	NULL;

+	sk->sk_splice_off	=	0;
 	sk->sk_peercred.pid 	=	0;

 	sk->sk_peercred.uid	=	-1;

diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c

index 19d7b42..cf3d367 100644

--- a/net/ipv4/tcp_ipv4.c

+++ b/net/ipv4/tcp_ipv4.c

@@ -1848,6 +1848,14 @@ void tcp_v4_destroy_sock(struct sock *sk)

 		sk->sk_sndmsg_page = NULL;

 	}
+	/*

+	 * If splice cached page exists, toss it.

+	 */

+	if (sk->sk_splice_page) {

+		__free_page(sk->sk_splice_page);

+		sk->sk_splice_page = NULL;

+	}

+

 	percpu_counter_dec(&tcp_sockets_allocated);

 }
--

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