netdev - Re: [RFC PATCH v4 net-next 1/4] tcp: replace cnt & rtt with struct in pkts

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <20150728034236.GA38906@Alexeis-MBP.westell.com>
Date:	Mon, 27 Jul 2015 20:42:37 -0700
From:	Alexei Starovoitov <alexei.starovoitov@...il.com>
To:	Lawrence Brakmo <brakmo@...com>
Cc:	Stephen Hemminger <stephen@...workplumber.org>,
	netdev <netdev@...r.kernel.org>,
	Kernel Team <Kernel-team@...com>,
	Neal Cardwell <ncardwell@...gle.com>,
	Eric Dumazet <eric.dumazet@...il.com>,
	Yuchung Cheng <ycheng@...gle.com>
Subject: Re: [RFC PATCH v4 net-next 1/4] tcp: replace cnt & rtt with struct
 in pkts_acked()

On Mon, Jul 27, 2015 at 07:30:39PM +0000, Lawrence Brakmo wrote:
> 
> 
> I prefer the cleanliness of passing a structure and don¹t 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.

--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html