linux-kernel - Re: [PATCH] x86: bpf_jit_comp: Reduce is

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Message-ID: <1417736103.2721.24.camel@perches.com>
Date:	Thu, 04 Dec 2014 15:35:03 -0800
From:	Joe Perches <joe@...ches.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	Alexei Starovoitov <alexei.starovoitov@...il.com>,
	Quentin Lambert <lambert.quentin@...il.com>,
	"David S. Miller" <davem@...emloft.net>,
	Alexey Kuznetsov <kuznet@....inr.ac.ru>,
	James Morris <jmorris@...ei.org>,
	Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
	Patrick McHardy <kaber@...sh.net>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] x86: bpf_jit_comp: Reduce is_ereg() code size

On Thu, 2014-12-04 at 15:14 -0800, Eric Dumazet wrote:
> On Thu, 2014-12-04 at 15:00 -0800, Joe Perches wrote:
> > Use the (1 << reg) & mask trick to reduce code size.
[]
> Really, the root cause of this is the 'inline' abuse in non fast paths
> for non trivial functions.

There is no object size change with is_ereg()
defined "static inline" or "static"

Curiously, if you mark it noinline, the size increases.

gcc 4.9.1, x86-64, -O2 no profiling support

$ size arch/x86/net/bpf_jit_comp.o.st*
   text	   data	    bss	    dec	    hex	filename
  10679	      4	      0	  10683	   29bb	arch/x86/net/bpf_jit_comp.o.static_inline
  11535	      4	      0	  11539	   2d13	arch/x86/net/bpf_jit_comp.o.static_noinline
  10679	      4	      0	  10683	   29bb	arch/x86/net/bpf_jit_comp.o.static_without_inline


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