From f1610480602a475323f9c335540d47b3a95c62fd Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Tue, 24 Mar 2020 19:23:21 -0700 Subject: [PATCH] net: use indirect call wrappers for skb_copy_datagram_iter() commit 29f3490ba9d2399d3d1b20c4aa74592d92bd4e11 upstream. TCP recvmsg() calls skb_copy_datagram_iter(), which calls an indirect function (cb pointing to simple_copy_to_iter()) for every MSS (fragment) present in the skb. CONFIG_RETPOLINE=y forces a very expensive operation that we can avoid thanks to indirect call wrappers. This patch gives a 13% increase of performance on a single flow, if the bottleneck is the thread reading the TCP socket. Fixes: 950fcaecd5cc ("datagram: consolidate datagram copy to iter helpers") Signed-off-by: Eric Dumazet Acked-by: Paolo Abeni Acked-by: Willem de Bruijn Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- net/core/datagram.c | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-) diff --git a/net/core/datagram.c b/net/core/datagram.c index da3c24e..189ad4c 100644 --- a/net/core/datagram.c +++ b/net/core/datagram.c @@ -51,6 +51,7 @@ #include #include #include +#include #include #include @@ -407,6 +408,11 @@ int skb_kill_datagram(struct sock *sk, struct sk_buff *skb, unsigned int flags) } EXPORT_SYMBOL(skb_kill_datagram); +INDIRECT_CALLABLE_DECLARE(static size_t simple_copy_to_iter(const void *addr, + size_t bytes, + void *data __always_unused, + struct iov_iter *i)); + static int __skb_datagram_iter(const struct sk_buff *skb, int offset, struct iov_iter *to, int len, bool fault_short, size_t (*cb)(const void *, size_t, void *, @@ -420,7 +426,8 @@ static int __skb_datagram_iter(const struct sk_buff *skb, int offset, if (copy > 0) { if (copy > len) copy = len; - n = cb(skb->data + offset, copy, data, to); + n = INDIRECT_CALL_1(cb, simple_copy_to_iter, + skb->data + offset, copy, data, to); offset += n; if (n != copy) goto short_copy; @@ -442,8 +449,9 @@ static int __skb_datagram_iter(const struct sk_buff *skb, int offset, if (copy > len) copy = len; - n = cb(vaddr + skb_frag_off(frag) + offset - start, - copy, data, to); + n = INDIRECT_CALL_1(cb, simple_copy_to_iter, + vaddr + skb_frag_off(frag) + offset - start, + copy, data, to); kunmap(page); offset += n; if (n != copy) -- 2.7.4