Re: [dpdk-dev] [PATCH] rte_flow: mark rte_flow_error_set as cold

[Stephen Hemminger <stephen@networkplumber.org>]

On Tue, 21 May 2019 08:01:53 +0000
"Van Haaren, Harry" <harry.van.haaren@intel.com> wrote:

> > -----Original Message-----
> > From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Stephen Hemminger
> > Sent: Monday, May 20, 2019 11:52 PM
> > To: adrien.mazarguil@6wind.com
> > Cc: dev@dpdk.org; Stephen Hemminger <stephen@networkplumber.org>
> > Subject: [dpdk-dev] [PATCH] rte_flow: mark rte_flow_error_set as cold
> > 
> > A minor optimization that save a few cycles during flow setup.
> > 
> > Use the GCC cold attribute for the rte_flow_error_set function.
> > This attribute implicitly marks all code paths that arrive at
> > this function as unlikely.  
> 
> Interesting - wasn't aware this is what the "cold" attribute does.
> 
> 
> >  lib/librte_ethdev/rte_flow.h | 8 +++++++-
> >  1 file changed, 7 insertions(+), 1 deletion(-)
> > 
> > diff --git a/lib/librte_ethdev/rte_flow.h b/lib/librte_ethdev/rte_flow.h
> > index 63f84fca65c4..dc821be43f19 100644
> > --- a/lib/librte_ethdev/rte_flow.h
> > +++ b/lib/librte_ethdev/rte_flow.h
> > @@ -2591,7 +2591,13 @@ rte_flow_error_set(struct rte_flow_error *error,
> >  		   int code,
> >  		   enum rte_flow_error_type type,
> >  		   const void *cause,
> > -		   const char *message);
> > +		   const char *message)
> > +#ifdef __GNUC__
> > +#if (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ > 2))
> > +	__attribute__((cold))
> > +#endif
> > +#endif
> > +	;  
> 
> 
> Would it be worth making an  __rte_attribute_cold  or similar?
> Less in-place #ifdefs and there are probably other locations in
> DPDK that would also benefit from such an annotation.
> 
> -Harry

I just cloned what was already on rte_log.