netdev - Re: [PATCH net-next] net: use indirect call wrappers for skb_copy_datagram

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Message-Id: <20200325.113102.661246567769402013.davem@davemloft.net>
Date:   Wed, 25 Mar 2020 11:31:02 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     edumazet@...gle.com
Cc:     netdev@...r.kernel.org, eric.dumazet@...il.com
Subject: Re: [PATCH net-next] net: use indirect call wrappers for
 skb_copy_datagram_iter()

From: Eric Dumazet <edumazet@...gle.com>
Date: Tue, 24 Mar 2020 19:23:21 -0700

> 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>

Applied, thanks Eric.