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net: speedup skb_splice_bits()

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Commit 35f3d14db (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: Eric Dumazet <edumazet@google.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Tom Herbert <therbert@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2012-04-22 12:26:16 +00:00 committed by David S. Miller
parent 1402d36601
commit 41c73a0d44
1 changed files with 19 additions and 11 deletions
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30
net/core/skbuff.c
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@ -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
get_page(page);
}
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;
}