Message-ID: <1447850630.22599.140.camel@edumazet-glaptop2.roam.corp.google.com>
Subject: Re: net-scm: Macro for special pattern?
From: Eric Dumazet <eric.dumazet@gmail.com>
To: SF Markus Elfring <elfring@users.sourceforge.net>
Cc: Daniel Borkmann <daniel@iogearbox.net>, netdev@vger.kernel.org,
        "David S. Miller" <davem@davemloft.net>, linux-kernel@vger.kernel.org,
        kernel-janitors@vger.kernel.org, Julia Lawall <julia.lawall@lip6.fr>
Date: Wed, 18 Nov 2015 04:43:50 -0800
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On Wed, 2015-11-18 at 08:45 +0100, SF Markus Elfring wrote:
> > You mean this likely() annotation of yours?
> 
> How do you think about to express the software design pattern
> which is applied at the mentioned source code place by a dedicated
> preprocessor macro?

likely()/unlikely() are not always applicable.

In the Ipv6 case I mentioned to you, it all depends if an application
for some reason absolutely wants the sockets to store the extra skb

There are seldom used socket options. _if_/_when_ they are used, a
likely()/unlikely() would give the wrong signal.

likely() should only be used in contexts we know better than branch
predictor/compiler.


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