Re: [PATCH] trace: reorder struct ring_buffer_per_cpu to removepadding on 64bit

[Steven Rostedt]

On Thu, 2010-03-25 at 11:27 +0000, Richard Kennedy wrote:
> Reorder structure to remove 8 bytes of padding on 64 bit builds.
> This shrinks the size to 128 bytes so allowing allocation from a smaller
> slab & needed one fewer cache lines.
> 

Thanks!

Just curious, did you use Arnaldo's pahole utility to find this?

-- Steve

> Signed-off-by: Richard Kennedy <richard@xxxxxxxxxxxxxxx>
> ----
> patch against 2.6.34-rc2
> compiled & booted on x86_64
> 
> regards
> Richard
> 
> diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
> index 05a9f83..421db5e 100644
> --- a/kernel/trace/ring_buffer.c
> +++ b/kernel/trace/ring_buffer.c
> @@ -422,6 +422,7 @@ int ring_buffer_print_page_header(struct trace_seq
> *s)
>   */
>  struct ring_buffer_per_cpu {
>  	int				cpu;
> +	atomic_t			record_disabled;
>  	struct ring_buffer		*buffer;
>  	spinlock_t			reader_lock;	/* serialize readers */
>  	arch_spinlock_t			lock;
> @@ -439,7 +440,6 @@ struct ring_buffer_per_cpu {
>  	unsigned long			read;
>  	u64				write_stamp;
>  	u64				read_stamp;
> -	atomic_t			record_disabled;
>  };
>  
>  struct ring_buffer {
> 
> 


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