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Commit 4fb66994 authored by Jarek Poplawski's avatar Jarek Poplawski Committed by David S. Miller
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net: Optimize memory usage when splicing from sockets. 



The recent fix of data corruption when splicing from sockets uses
memory very inefficiently allocating a new page to copy each chunk of
linear part of skb. This patch uses the same page until it's full
(almost) by caching the page in sk_sndmsg_page field.

With changes from David S. Miller <davem@davemloft.net>

Signed-off-by: default avatarJarek Poplawski <jarkao2@gmail.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 31f45747

net/core/skbuff.c

+36 −11
Original line number Diff line number Diff line
@@ -1333,14 +1333,39 @@ static void sock_spd_release(struct splice_pipe_desc *spd, unsigned int i) 
	put_page(spd->pages[i]);

}



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

					  unsigned int offset)

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

					  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_sndmsg_page;

	unsigned int off;



	if (!p) {

new_page:

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

		if (!p)

			return NULL;

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



		off = sk->sk_sndmsg_off = 0;

		/* hold one ref to this page until it's full */

	} else {

		unsigned int mlen;



		off = sk->sk_sndmsg_off;

		mlen = PAGE_SIZE - off;

		if (mlen < 64 && mlen < *len) {

			put_page(p);

			goto new_page;

		}



		*len = min_t(unsigned int, *len, mlen);

	}



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

	sk->sk_sndmsg_off += *len;

	*offset = off;

	get_page(p);



	return p;

}
@@ -1349,21 +1374,21 @@ static inline struct page *linear_to_page(struct page *page, unsigned int len, 
 * Fill page/offset/length into spd, if it can hold more pages.

 */

static inline int spd_fill_page(struct splice_pipe_desc *spd, struct page *page,

				unsigned int len, unsigned int offset,

				unsigned int *len, unsigned int offset,

				struct sk_buff *skb, int linear)

{

	if (unlikely(spd->nr_pages == PIPE_BUFFERS))

		return 1;



	if (linear) {

		page = linear_to_page(page, len, offset);

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

		if (!page)

			return 1;

	} else

		get_page(page);



	spd->pages[spd->nr_pages] = page;

	spd->partial[spd->nr_pages].len = len;

	spd->partial[spd->nr_pages].len = *len;

	spd->partial[spd->nr_pages].offset = offset;

	spd->nr_pages++;
@@ -1405,7 +1430,7 @@ static inline int __splice_segment(struct page *page, unsigned int poff, 
		/* the linear region may spread across several pages  */

		flen = min_t(unsigned int, flen, PAGE_SIZE - poff);



		if (spd_fill_page(spd, page, flen, poff, skb, linear))

		if (spd_fill_page(spd, page, &flen, poff, skb, linear))

			return 1;



		__segment_seek(&page, &poff, &plen, flen);