Re: [PATCH] perf c2c: Fix sorting.

[Jiri Olsa]

On Wed, Jan 08, 2020 at 08:30:30PM -0800, Andres Freund wrote:
> Commit 722ddfde366f ("perf tools: Fix time sorting") changed -
> correctly so - hist_entry__sort to return int64. Unfortunately several
> of the builtin-c2c.c comparison routines only happened to work due the
> cast caused by the wrong return type.
> 
> This causes meaningless ordering of both the cacheline list, and the
> cacheline details page. E.g a simple
>   perf c2c record -a sleep 3
>   perf c2c report
> will result in cacheline table like
>   =================================================
>              Shared Data Cache Line Table
>   =================================================
>   #
>   #        ----------- Cacheline ----------    Total      Tot  ----- LLC Load Hitm -----  ---- Store Reference ----  --- Load Dram ----      LLC    Total  ----- Core Load Hit -----  -- LLC Load Hit --
>   # Index             Address  Node  PA cnt  records     Hitm    Total      Lcl      Rmt    Total    L1Hit   L1Miss       Lcl       Rmt  Ld Miss    Loads       FB       L1       L2       Llc       Rmt
>   # .....  ..................  ....  ......  .......  .......  .......  .......  .......  .......  .......  .......  ........  ........  .......  .......  .......  .......  .......  ........  ........
>   #
>         0      0x7f0d27ffba00   N/A       0       52    0.12%       13        6        7       12       12        0         0         7       14       40        4       16        0         0         0
>         1      0x7f0d27ff61c0   N/A       0     6353   14.04%     1475      801      674      779      779        0         0       718     1392     5574     1299     1967        0       115         0
>         2      0x7f0d26d3ec80   N/A       0       71    0.15%       16        4       12       13       13        0         0        12       24       58        1       20        0         9         0
>         3      0x7f0d26d3ec00   N/A       0       98    0.22%       23       17        6       19       19        0         0         6       12       79        0       40        0        10         0
> i.e. with the list not being ordered by Total Hitm.
> 
> Fixes: 722ddfde366f ("perf tools: Fix time sorting")
> Signed-off-by: Andres Freund <andres@xxxxxxxxxxx>
> Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
> Cc: Andi Kleen <ak@xxxxxxxxxxxxxxx>
> Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
> Cc: Alexander Shishkin <alexander.shishkin@xxxxxxxxxxxxxxx>
> Cc: Michael Petlan <mpetlan@xxxxxxxxxx>
> Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx # v3.16+
> ---
>  tools/perf/builtin-c2c.c | 10 ++++++----
>  1 file changed, 6 insertions(+), 4 deletions(-)
> 
> diff --git a/tools/perf/builtin-c2c.c b/tools/perf/builtin-c2c.c
> index e69f44941aad..f2e9d2b1b913 100644
> --- a/tools/perf/builtin-c2c.c
> +++ b/tools/perf/builtin-c2c.c
> @@ -595,8 +595,8 @@ tot_hitm_cmp(struct perf_hpp_fmt *fmt __maybe_unused,
>  {
>  	struct c2c_hist_entry *c2c_left;
>  	struct c2c_hist_entry *c2c_right;
> -	unsigned int tot_hitm_left;
> -	unsigned int tot_hitm_right;
> +	uint64_t tot_hitm_left;
> +	uint64_t tot_hitm_right;

that change looks right, but I can't see how that could
happened because of change in Fixes: tag

was the return statement of this function:

        return tot_hitm_left - tot_hitm_right;

considered to be 'unsigned int' and then converted to int64_t,
which would treat negative 'unsigned int' as big positive 'int64_t'?

thanks,
jirka

>  
>  	c2c_left  = container_of(left, struct c2c_hist_entry, he);
>  	c2c_right = container_of(right, struct c2c_hist_entry, he);
> @@ -629,7 +629,8 @@ __f ## _cmp(struct perf_hpp_fmt *fmt __maybe_unused,			\
>  									\
>  	c2c_left  = container_of(left, struct c2c_hist_entry, he);	\
>  	c2c_right = container_of(right, struct c2c_hist_entry, he);	\
> -	return c2c_left->stats.__f - c2c_right->stats.__f;		\
> +	return (uint64_t) c2c_left->stats.__f -				\
> +	       (uint64_t) c2c_right->stats.__f;				\
>  }
>  
>  #define STAT_FN(__f)		\
> @@ -682,7 +683,8 @@ ld_llcmiss_cmp(struct perf_hpp_fmt *fmt __maybe_unused,
>  	c2c_left  = container_of(left, struct c2c_hist_entry, he);
>  	c2c_right = container_of(right, struct c2c_hist_entry, he);
>  
> -	return llc_miss(&c2c_left->stats) - llc_miss(&c2c_right->stats);
> +	return (uint64_t) llc_miss(&c2c_left->stats) -
> +	       (uint64_t) llc_miss(&c2c_right->stats);
>  }
>  
>  static uint64_t total_records(struct c2c_stats *stats)
> -- 
> 2.25.0.rc1
>