linux-kernel - Need ack from sparc maintainer (was: [PATCH 1/4] jump label: introduce static

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Date:	Wed, 16 Mar 2011 16:06:13 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Jason Baron <jbaron@...hat.com>
Cc:	peterz@...radead.org, hpa@...or.com, mathieu.desnoyers@...ymtl.ca,
	mingo@...e.hu, tglx@...utronix.de, andi@...stfloor.org,
	roland@...hat.com, rth@...hat.com, masami.hiramatsu.pt@...achi.com,
	fweisbec@...il.com, avi@...hat.com, davem@...emloft.net,
	sam@...nborg.org, ddaney@...iumnetworks.com,
	michael@...erman.id.au, ralf@...ux-mips.org,
	jang@...ux.vnet.ibm.com, schwidefsky@...ibm.com,
	linux-kernel@...r.kernel.org
Subject: Need ack from sparc maintainer (was: [PATCH 1/4] jump label:
 introduce static_branch() interface)

On Wed, 2011-03-16 at 15:58 -0400, Jason Baron wrote:
> Introduce:
> 
> static __always_inline bool static_branch(struct jump_label_key *key);
> 
> instead of the old JUMP_LABEL(key, label) macro.
> 
> In this way, jump labels become really easy to use:
> 
> Define:
> 
>         struct jump_label_key jump_key;
> 
> Can be used as:
> 
>         if (static_branch(&jump_key))
>                 do unlikely code
> 
> enable/disale via:
> 
>         jump_label_inc(&jump_key);
>         jump_label_dec(&jump_key);
> 
> that's it!
> 
> For the jump labels disabled case, the static_branch() becomes an
> atomic_read(), and jump_label_inc()/dec() are simply atomic_inc(),
> atomic_dec() operations. We show testing results for this change below.
> 
> Thanks to H. Peter Anvin for suggesting the 'static_branch()' construct.
> 
> Since we now require a 'struct jump_label_key *key', we can store a pointer into
> the jump table addresses. In this way, we can enable/disable jump labels, in
> basically constant time. This change allows us to completely remove the previous
> hashtable scheme. Thanks to Peter Zijlstra for this re-write.
> 
> Testing:
> 
> I ran a series of 'tbench 20' runs 5 times (with reboots) for 3
> configurations, where tracepoints were disabled.
> 
> jump label configured in
> avg: 815.6
> 
> jump label *not* configured in (using atomic reads)
> avg: 800.1
> 
> jump label *not* configured in (regular reads)
> avg: 803.4
> 
> 
> Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
> Signed-off-by: Jason Baron <jbaron@...hat.com>
> Suggested-by: H. Peter Anvin <hpa@...ux.intel.com>
> Tested-by: David Daney <ddaney@...iumnetworks.com>
> Acked-by: Ralf Baechle <ralf@...ux-mips.org>
> ---
>  arch/mips/include/asm/jump_label.h  |   22 +-
>  arch/sparc/include/asm/jump_label.h |   25 +-

Hi David,

Can you give your Acked-by for this change.

Thanks,

-- Steve

>  arch/x86/include/asm/alternative.h  |    3 +-
>  arch/x86/include/asm/jump_label.h   |   26 +-
>  arch/x86/kernel/alternative.c       |    2 +-
>  arch/x86/kernel/module.c            |    1 +
>  include/asm-generic/vmlinux.lds.h   |   14 +-
>  include/linux/dynamic_debug.h       |    2 -
>  include/linux/jump_label.h          |   89 ++++---
>  include/linux/jump_label_ref.h      |   44 ---
>  include/linux/perf_event.h          |   26 +-
>  include/linux/tracepoint.h          |   22 +-
>  kernel/jump_label.c                 |  539 ++++++++++++++---------------------
>  kernel/perf_event.c                 |    4 +-
>  kernel/tracepoint.c                 |   23 +-
>  15 files changed, 356 insertions(+), 486 deletions(-)
>  delete mode 100644 include/linux/jump_label_ref.h
> 


> diff --git a/arch/sparc/include/asm/jump_label.h b/arch/sparc/include/asm/jump_label.h
> index 427d468..fc73a82 100644
> --- a/arch/sparc/include/asm/jump_label.h
> +++ b/arch/sparc/include/asm/jump_label.h
> @@ -7,17 +7,20 @@
>  
>  #define JUMP_LABEL_NOP_SIZE 4
>  
> -#define JUMP_LABEL(key, label)					\
> -	do {							\
> -		asm goto("1:\n\t"				\
> -			 "nop\n\t"				\
> -			 "nop\n\t"				\
> -			 ".pushsection __jump_table,  \"a\"\n\t"\
> -			 ".align 4\n\t"				\
> -			 ".word 1b, %l[" #label "], %c0\n\t"	\
> -			 ".popsection \n\t"			\
> -			 : :  "i" (key) :  : label);\
> -	} while (0)
> +static __always_inline bool arch_static_branch(struct jump_label_key *key)
> +{
> +		asm goto("1:\n\t"
> +			 "nop\n\t"
> +			 "nop\n\t"
> +			 ".pushsection __jump_table,  \"aw\"\n\t"
> +			 ".align 4\n\t"
> +			 ".word 1b, %l[l_yes], %c0\n\t"
> +			 ".popsection \n\t"
> +			 : :  "i" (key) : : l_yes);
> +	return false;
> +l_yes:
> +	return true;
> +}
>  


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