Re: [dpdk-dev] [PATCH v7 4/8] vhost: rxtx: use queue id instead of constant ring index

[Thomas Monjalon <thomas.monjalon@6wind.com>]

2015-10-21 08:47, Stephen Hemminger:
> On Wed, 21 Oct 2015 09:38:37 +0000
> "Ananyev, Konstantin" <konstantin.ananyev@intel.com> wrote:
> > I also don't understand what's wrong with using 'always_inline' here.
> > As I understand the author wants compiler to *always inline* that function.
> > So seems perfectly ok to use it here.
> > As I remember just 'inline' is sort of recommendation that compiler is free to ignore.
> > Konstantin 
> 
> I follow Linux/Linus advice and resist the urge to add strong inlining.
> The compiler does a good job of deciding to inline, and many times
> the reason it chooses for not inlining are quite good like:
>   - the code is on an unlikely branch
>   - register pressure means inlining would mean the code would be worse
> 
> Therefore my rules are:
>   * only use inline for small functions. Let compiler decide on larger static funcs
>   * write code where most functions are static (localized scope) where compiler
>     can decide
>   * reserve always inline for things that access hardware and would break if not inlined.

It would be interesting to do some benchmarks with/without "always" keyword
and add these rules in the coding style guide.