Re: [PATCH 3/3] dwarves print: Keep global cacheline in struct conf_fprintf

[Arnaldo Carvalho de Melo <acme-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>]

Em Tue, Dec 08, 2015 at 11:47:06PM +0100, Jiri Olsa escreveu:
> Together with adding cconf->base_offset to sums used
> for cacheline computation, this ensures proper cacheline
> number to be printed for nested struct. Note possitions
> of 'cacheline' lines in following outputs.
> 
> Before:
>   $ pahole -C task_struct -E ~/kernel/linux-perf-local/vmlinux
>   struct task_struct {
>         volatile long int          state;                                                /*     0     8 */
> 
>         --- First cacheline is ok
> 
>         struct task_struct *       last_wakee;                                           /*    56     8 */
>         /* --- cacheline 1 boundary (64 bytes) --- */
>         int                        wake_cpu;                                             /*    64     4 */
> 
>         ...
> 
>         const struct sched_class  * sched_class;                                         /*    88     8 */
>         struct sched_entity {
>                 struct load_weight {
>                         long unsigned int weight;                                        /*    96     8 */
>                         /* typedef u32 */ unsigned int inv_weight;                       /*   104     4 */
>                 } load; /*    96    16 */
> 
>                 --- Second one is still in relative mode and gives wrong
>                     alignment in wrt task_struct start
> 
>                 unsigned int       on_rq;                                                /*   152     4 */
>                 /* --- cacheline 1 boundary (64 bytes) --- */

Ok, this is a bug...

>                 /* typedef u64 */ long long unsigned int exec_start;                     /*   160     8 */
>                 /* typedef u64 */ long long unsigned int sum_exec_runtime;               /*   168     8 */
>        ...
> 
> After:
>   $ pahole -C task_struct -E ~/kernel/linux-perf-local/vmlinux
> 
>    struct task_struct {
>         volatile long int          state;                                                /*     0     8 */
> 
>         --- First cacheline is ok
> 
>         struct task_struct *       last_wakee;                                           /*    56     8 */
>         /* --- cacheline 1 boundary (64 bytes) --- */
>         int                        wake_cpu;                                             /*    64     4 */
> 
>         ...
> 
>         const struct sched_class  * sched_class;                                         /*    88     8 */
>         struct sched_entity {
>                 struct load_weight {
>                         long unsigned int weight;                                        /*    96     8 */
>                         /* typedef u32 */ unsigned int inv_weight;                       /*   104     4 */
>                 } load; /*    96    16 */
>                 struct rb_node {
>                         long unsigned int __rb_parent_color;                             /*   112     8 */
>                         struct rb_node * rb_right;                                       /*   120     8 */
>                         /* --- cacheline 2 boundary (128 bytes) --- */

Which seems fixed here, but...

>                         struct rb_node * rb_left;                                        /*   128     8 */
>                 } run_node; /*   112    24 */
> 
>                 --- Second one is still in relative mode and gives wrong
>                     alignment in wrt task_struct start

... why this one is buggy still? I.e. it should be fixed in such a way
that when we go recursively expanding structs, we know what is the
current cacheline we're on.

- Arnaldo

> 
>                 /* --- cacheline 2 boundary (128 bytes) was 8 bytes ago --- */
>                 struct list_head {
>                         struct list_head * next;                                         /*   136     8 */
>                         struct list_head * prev;                                         /*   144     8 */
>                 } group_node; /*   136    16 */
>        ...
> 
> Signed-off-by: Jiri Olsa <jolsa-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
> ---
>  dwarves.h         |  1 +
>  dwarves_fprintf.c | 25 ++++++++++---------------
>  2 files changed, 11 insertions(+), 15 deletions(-)
> 
> diff --git a/dwarves.h b/dwarves.h
> index 73fec8ac614a..44ebf8384b9c 100644
> --- a/dwarves.h
> +++ b/dwarves.h
> @@ -56,6 +56,7 @@ struct conf_fprintf {
>  	int32_t	   type_spacing;
>  	int32_t	   name_spacing;
>  	uint32_t   base_offset;
> +	uint32_t   base_cacheline;
>  	uint8_t	   indent;
>  	uint8_t	   expand_types:1;
>  	uint8_t	   expand_pointers:1;
> diff --git a/dwarves_fprintf.c b/dwarves_fprintf.c
> index 2d114210831a..72d8b08bf235 100644
> --- a/dwarves_fprintf.c
> +++ b/dwarves_fprintf.c
> @@ -1118,22 +1118,21 @@ size_t function__fprintf_stats(const struct tag *tag, const struct cu *cu,
>  	return printed + fprintf(fp, " */\n");
>  }
>  
> -static size_t class__fprintf_cacheline_boundary(uint32_t last_cacheline,
> -						size_t sum, size_t sum_holes,
> +static size_t class__fprintf_cacheline_boundary(size_t sum, size_t sum_holes,
>  						uint8_t *newline,
> -						uint32_t *cacheline,
>  						struct conf_fprintf *cconf,
>  						FILE *fp)
>  {
> -	const size_t real_sum = sum + sum_holes;
> +	const size_t real_sum = sum + sum_holes + cconf->base_offset;
>  	size_t printed = 0;
> +	uint32_t cacheline = real_sum / cacheline_size;
>  
> -	*cacheline = real_sum / cacheline_size;
> -
> -	if (*cacheline > last_cacheline) {
> +	if (cacheline != cconf->base_cacheline) {
>  		const uint32_t cacheline_pos = real_sum % cacheline_size;
>  		const uint32_t cacheline_in_bytes = real_sum - cacheline_pos;
>  
> +		cconf->base_cacheline = cacheline;
> +
>  		if (*newline) {
>  			fputc('\n', fp);
>  			*newline = 0;
> @@ -1144,12 +1143,12 @@ static size_t class__fprintf_cacheline_boundary(uint32_t last_cacheline,
>  
>  		if (cacheline_pos == 0)
>  			printed += fprintf(fp, "/* --- cacheline %u boundary "
> -					   "(%u bytes) --- */\n", *cacheline,
> +					   "(%u bytes) --- */\n", cacheline,
>  					   cacheline_in_bytes);
>  		else
>  			printed += fprintf(fp, "/* --- cacheline %u boundary "
>  					   "(%u bytes) was %u bytes ago --- "
> -					   "*/\n", *cacheline,
> +					   "*/\n", cacheline,
>  					   cacheline_in_bytes, cacheline_pos);
>  	}
>  	return printed;
> @@ -1284,10 +1283,8 @@ size_t class__fprintf(struct class *class, const struct cu *cu,
>  		    pos->byte_offset != last->byte_offset &&
>  		    !cconf.suppress_comments)
>  			printed +=
> -			    class__fprintf_cacheline_boundary(last_cacheline,
> -							      sum, sum_holes,
> +			    class__fprintf_cacheline_boundary(sum, sum_holes,
>  							      &newline,
> -							      &last_cacheline,
>  							      &cconf,
>  							      fp);
>  		/*
> @@ -1474,10 +1471,8 @@ size_t class__fprintf(struct class *class, const struct cu *cu,
>  	}
>  
>  	if (!cconf.suppress_comments)
> -		printed += class__fprintf_cacheline_boundary(last_cacheline,
> -							     sum, sum_holes,
> +		printed += class__fprintf_cacheline_boundary(sum, sum_holes,
>  							     &newline,
> -							     &last_cacheline,
>  							     &cconf, fp);
>  	if (!cconf.show_only_data_members)
>  		class__vtable_fprintf(class, cu, &cconf, fp);
> -- 
> 2.4.3
> 
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