netdev - Re: [net-next PATCH 3/4] net: avoid false perf interpretations in frag code

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Date:	Thu, 25 Apr 2013 12:57:08 +0200
From:	Jesper Dangaard Brouer <brouer@...hat.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	"David S. Miller" <davem@...emloft.net>,
	Hannes Frederic Sowa <hannes@...essinduktion.org>,
	netdev@...r.kernel.org
Subject: Re: [net-next PATCH 3/4] net: avoid false perf interpretations in
 frag code

On Wed, 2013-04-24 at 16:48 -0700, Eric Dumazet wrote:
> On Wed, 2013-04-24 at 17:48 +0200, Jesper Dangaard Brouer wrote:
> > The compiler make us misinterpret performance issues in the frag code,
> > because its auto inlining functions.  Lets instead do explicit
> > inlining to make this situation obvious to the programmer.
> > 
> > The function inet_frag_find() get the perf blame, because auto
> > inlining of the functions inet_frag_create(), inet_frag_alloc() and
> > inet_frag_intern().
> > 
> > My solution is to explicit inline inet_frag_alloc() and
> > inet_frag_intern(), but explicitly "noinline" inet_frag_create(),
> > in-order to make it explicit to the performance engineer, that
> > creation phase is a bottleneck. Then, when reading the code the
> > programmer should notice the inline, and see the bottleneck is really
> > located in inet_frag_intern().
> > 
> > Signed-off-by: Jesper Dangaard Brouer <brouer@...hat.com>
> > ---
> 
> There is no way we add inline/noinline attributes to help developers to
> use performance tools.

I take that as a NACK

Would we add the "inlines" only to the code, to make it clear what is
happening in the code?


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