linux-kernel - Re: [PATCH 3/3] ftrace: Constify ftrace_profile

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Date:	Tue, 09 Apr 2013 19:03:31 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Namhyung Kim <namhyung@...nel.org>
Cc:	Frederic Weisbecker <fweisbec@...il.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Namhyung Kim <namhyung.kim@....com>
Subject: Re: [PATCH 3/3] ftrace: Constify ftrace_profile_bits

On Mon, 2013-04-01 at 21:46 +0900, Namhyung Kim wrote:
> From: Namhyung Kim <namhyung.kim@....com>
> 
> It seems that function profiler's hash size is fixed at 1024.
> Make the ftrace_profile_bits const and update hash size macro.
> 
> Signed-off-by: Namhyung Kim <namhyung@...nel.org>
> ---
>  kernel/trace/ftrace.c | 13 ++++---------
>  1 file changed, 4 insertions(+), 9 deletions(-)
> 
> diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
> index d38ad7145f2f..08bbc5952a3a 100644
> --- a/kernel/trace/ftrace.c
> +++ b/kernel/trace/ftrace.c
> @@ -486,7 +486,6 @@ struct ftrace_profile_stat {
>  #define PROFILES_PER_PAGE					\
>  	(PROFILE_RECORDS_SIZE / sizeof(struct ftrace_profile))
>  
> -static int ftrace_profile_bits __read_mostly;
>  static int ftrace_profile_enabled __read_mostly;
>  
>  /* ftrace_profile_lock - synchronize the enable and disable of the profiler */
> @@ -494,7 +493,10 @@ static DEFINE_MUTEX(ftrace_profile_lock);
>  
>  static DEFINE_PER_CPU(struct ftrace_profile_stat, ftrace_profile_stats);
>  
> -#define FTRACE_PROFILE_HASH_SIZE 1024 /* must be power of 2 */
> +#define FTRACE_PROFILE_HASH_BITS 10
> +#define FTRACE_PROFILE_HASH_SIZE (1 << FTRACE_PROFILE_HASH_BITS)
> +
> +static const int ftrace_profile_bits = FTRACE_PROFILE_HASH_BITS;

Actually, can you resubmit this, and remove ftrace_profile_bits totally,
and just use FTRACE_PROFILE_HASH_BITS directly?

Thanks,

-- Steve

>  
>  static void *
>  function_stat_next(void *v, int idx)
> @@ -724,13 +726,6 @@ static int ftrace_profile_init_cpu(int cpu)
>  	if (!stat->hash)
>  		return -ENOMEM;
>  
> -	if (!ftrace_profile_bits) {
> -		size--;
> -
> -		for (; size; size >>= 1)
> -			ftrace_profile_bits++;
> -	}
> -
>  	/* Preallocate the function profiling pages */
>  	if (ftrace_profile_pages_init(stat) < 0) {
>  		kfree(stat->hash);


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