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ipv4: factorize sk_wmem_alloc updates done by __ip_append_data()

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While testing my inet defrag changes, I found that the senders
could spend ~20% of cpu cycles in skb_set_owner_w() updating
sk->sk_wmem_alloc for every fragment they cook.

The solution to this problem is to use alloc_skb() instead
of sock_wmalloc() and manually perform a single sk_wmem_alloc change.

Similar change for IPv6 is provided in following patch.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2018-03-31 13:16:25 -07:00 committed by David S. Miller
parent c072550205
commit 694aba690d
1 changed files with 12 additions and 5 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

17
net/ipv4/ip_output.c
View file

@ -876,6 +876,7 @@ static int __ip_append_data(struct sock *sk,
unsigned int maxfraglen, fragheaderlen, maxnonfragsize;
int csummode = CHECKSUM_NONE;
struct rtable *rt = (struct rtable *)cork->dst;
unsigned int wmem_alloc_delta = 0;
u32 tskey = 0;
skb = skb_peek_tail(queue);
@ -971,11 +972,10 @@ static int __ip_append_data(struct sock *sk,
(flags & MSG_DONTWAIT), &err);
} else {
skb = NULL;
if (refcount_read(&sk->sk_wmem_alloc) <=
if (refcount_read(&sk->sk_wmem_alloc) + wmem_alloc_delta <=
2 * sk->sk_sndbuf)
skb = sock_wmalloc(sk,
alloclen + hh_len + 15, 1,
sk->sk_allocation);
skb = alloc_skb(alloclen + hh_len + 15,
sk->sk_allocation);
if (unlikely(!skb))
err = -ENOBUFS;
}
@ -1033,6 +1033,11 @@ static int __ip_append_data(struct sock *sk,
/*
* Put the packet on the pending queue.
*/
if (!skb->destructor) {
skb->destructor = sock_wfree;
skb->sk = sk;
wmem_alloc_delta += skb->truesize;
}
__skb_queue_tail(queue, skb);
continue;
}
@ -1079,12 +1084,13 @@ static int __ip_append_data(struct sock *sk,
skb->len += copy;
skb->data_len += copy;
skb->truesize += copy;
refcount_add(copy, &sk->sk_wmem_alloc);
wmem_alloc_delta += copy;
}
offset += copy;
length -= copy;
}
refcount_add(wmem_alloc_delta, &sk->sk_wmem_alloc);
return 0;
error_efault:
@ -1092,6 +1098,7 @@ static int __ip_append_data(struct sock *sk,
error:
cork->length -= length;
IP_INC_STATS(sock_net(sk), IPSTATS_MIB_OUTDISCARDS);
refcount_add(wmem_alloc_delta, &sk->sk_wmem_alloc);
return err;
}