From mboxrd@z Thu Jan  1 00:00:00 1970
From: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Subject: Re: [RFC PATCH v4 net-next 1/4] tcp: replace cnt & rtt with struct
 in pkts_acked()
Date: Mon, 27 Jul 2015 20:42:37 -0700
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Cc: Stephen Hemminger <stephen@networkplumber.org>,
	netdev <netdev@vger.kernel.org>,
	Kernel Team <Kernel-team@fb.com>,
	Neal Cardwell <ncardwell@google.com>,
	Eric Dumazet <eric.dumazet@gmail.com>,
	Yuchung Cheng <ycheng@google.com>
To: Lawrence Brakmo <brakmo@fb.com>
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On Mon, Jul 27, 2015 at 07:30:39PM +0000, Lawrence Brakmo wrote:
>=20
>=20
> I prefer the cleanliness of passing a structure and don=B9t think the
> overhead will be significant enough to worry about it.
> Will the compiler pass struct values in registers if the struct is
> passed by value?

In passing struct by value it's not a matter of optimization but C abi.
On sparc even 4-byte structs are passed by reference which creates
an extra copy of the same struct on stack.
Struct returns are even worse. I would always pass structs by reference
in C. C++ is different matter.