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Commit 41c73a0d authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
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net: speedup skb_splice_bits() 



Commit 35f3d14d (pipe: add support for shrinking and growing pipes)
added a slowdown for splice(socket -> pipe), as we might grow the spd
used in skb_splice_bits() for each skb we process in splice() syscall.

Its not needed since skb lengths are capped. The default on-stack arrays
are more than enough.

Use MAX_SKB_FRAGS instead of PIPE_DEF_BUFFERS to describe the reasonable
limit per skb.

Add coalescing support to help splicing of GRO skbs built from linear
skbs (linked into frag_list)

Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Tom Herbert <therbert@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 1402d366

net/core/skbuff.c

+19 −11
Original line number Diff line number Diff line
@@ -1581,11 +1581,20 @@ static inline struct page *linear_to_page(struct page *page, unsigned int *len, 
	memcpy(page_address(p) + off, page_address(page) + *offset, *len);

	sk->sk_sndmsg_off += *len;

	*offset = off;

	get_page(p);



	return p;

}



static bool spd_can_coalesce(const struct splice_pipe_desc *spd,

			     struct page *page,

			     unsigned int offset)

{

	return	spd->nr_pages &&

		spd->pages[spd->nr_pages - 1] == page &&

		(spd->partial[spd->nr_pages - 1].offset +

		 spd->partial[spd->nr_pages - 1].len == offset);

}



/*

 * Fill page/offset/length into spd, if it can hold more pages.

 */
@@ -1595,16 +1604,19 @@ static inline int spd_fill_page(struct splice_pipe_desc *spd, 
				struct sk_buff *skb, int linear,

				struct sock *sk)

{

	if (unlikely(spd->nr_pages == pipe->buffers))

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

		return 1;



	if (linear) {

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

		if (!page)

			return 1;

	} else

	}

	if (spd_can_coalesce(spd, page, offset)) {

		spd->partial[spd->nr_pages - 1].len += *len;

		return 0;

	}

	get_page(page);



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

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

	spd->partial[spd->nr_pages].offset = offset;
@@ -1710,8 +1722,8 @@ int skb_splice_bits(struct sk_buff *skb, unsigned int offset, 
		    struct pipe_inode_info *pipe, unsigned int tlen,

		    unsigned int flags)

{

	struct partial_page partial[PIPE_DEF_BUFFERS];

	struct page *pages[PIPE_DEF_BUFFERS];

	struct partial_page partial[MAX_SKB_FRAGS];

	struct page *pages[MAX_SKB_FRAGS];

	struct splice_pipe_desc spd = {

		.pages = pages,

		.partial = partial,
@@ -1723,9 +1735,6 @@ int skb_splice_bits(struct sk_buff *skb, unsigned int offset, 
	struct sock *sk = skb->sk;

	int ret = 0;



	if (splice_grow_spd(pipe, &spd))

		return -ENOMEM;



	/*

	 * __skb_splice_bits() only fails if the output has no room left,

	 * so no point in going over the frag_list for the error case.
@@ -1761,7 +1770,6 @@ int skb_splice_bits(struct sk_buff *skb, unsigned int offset, 
		lock_sock(sk);

	}



	splice_shrink_spd(pipe, &spd);

	return ret;

}