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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.

Fixes: 950fcaecd5 ("datagram: consolidate datagram copy to iter helpers")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Paolo Abeni <pabeni@redhat.com>
Acked-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2020-03-24 19:23:21 -07:00 committed by David S. Miller
parent fab90c8202
commit 29f3490ba9
1 changed files with 11 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

14
net/core/datagram.c
View File

@ -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)