linux-kernel - Re: [PATCH v1 06/22] powerpc/ftrace: Inline ftrace_modify

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Message-Id: <1650261933.e8kr43zvw0.naveen@linux.ibm.com>
Date:   Mon, 18 Apr 2022 11:37:24 +0530
From:   "Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>
To:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Christophe Leroy <christophe.leroy@...roup.eu>,
        Ingo Molnar <mingo@...hat.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Paul Mackerras <paulus@...ba.org>,
        Steven Rostedt <rostedt@...dmis.org>
Cc:     linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH v1 06/22] powerpc/ftrace: Inline ftrace_modify_code()

Christophe Leroy wrote:
> Inlining ftrace_modify_code(), it increases a bit the
> size of ftrace code but brings 5% improvment on ftrace
> activation.
> 
> Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
> ---
>  arch/powerpc/kernel/trace/ftrace.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/powerpc/kernel/trace/ftrace.c b/arch/powerpc/kernel/trace/ftrace.c
> index 41c45b9c7f39..98e82fa4980f 100644
> --- a/arch/powerpc/kernel/trace/ftrace.c
> +++ b/arch/powerpc/kernel/trace/ftrace.c
> @@ -53,7 +53,7 @@ ftrace_call_replace(unsigned long ip, unsigned long addr, int link)
>  	return op;
>  }
> 
> -static int
> +static inline int
>  ftrace_modify_code(unsigned long ip, ppc_inst_t old, ppc_inst_t new)
>  {
>  	ppc_inst_t replaced;

I thought gcc was free to inline functions without the need for 
'inline'. Don't you see this being inlined otherwise?

On the flip side, don't we need __always_inline if we want to force 
inlining?


- Naveen