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Date: Tue, 24 Mar 2020 19:23:21 -0700 From: Eric Dumazet <edumazet@...gle.com> To: "David S . Miller" <davem@...emloft.net> Cc: netdev <netdev@...r.kernel.org>, Eric Dumazet <edumazet@...gle.com>, Eric Dumazet <eric.dumazet@...il.com> Subject: [PATCH net-next] net: use indirect call wrappers for skb_copy_datagram_iter() 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. Signed-off-by: Eric Dumazet <edumazet@...gle.com> --- 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 4213081c6ed3d4fda69501641a8c76e041f26b42..639745d4f3b94a248da9a685f45158410a85bec7 100644 --- a/net/core/datagram.c +++ b/net/core/datagram.c @@ -51,6 +51,7 @@ #include <linux/slab.h> #include <linux/pagemap.h> #include <linux/uio.h> +#include <linux/indirect_call_wrapper.h> #include <net/protocol.h> #include <linux/skbuff.h> @@ -403,6 +404,11 @@ 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 *, @@ -416,7 +422,8 @@ 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; @@ -438,8 +445,9 @@ 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) -- 2.25.1.696.g5e7596f4ac-goog
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