Re: [PATCH] perf hist: Fix width calculation in hpp__fmt()

[James Clark]

On 08/01/2025 6:59 am, Dmitry Vyukov wrote:
> hpp__width_fn() round up width to length of the field name,
> hpp__fmt() should do it too. Otherwise, the numbers may
> end up unaligned if the field name is long.
>
> Signed-off-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
> Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
> Cc: Ian Rogers <irogers@xxxxxxxxxx>
> Cc: linux-perf-users@xxxxxxxxxxxxxxx
> Cc: linux-kernel@xxxxxxxxxxxxxxx
> ---
>   tools/perf/ui/hist.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/tools/perf/ui/hist.c b/tools/perf/ui/hist.c
> index e5491995adf08..34fda1d5eccb4 100644
> --- a/tools/perf/ui/hist.c
> +++ b/tools/perf/ui/hist.c
> @@ -121,7 +121,7 @@ int hpp__fmt(struct perf_hpp_fmt *fmt, struct perf_hpp *hpp,
>   	     const char *fmtstr, hpp_snprint_fn print_fn,
>   	     enum perf_hpp_fmt_type fmtype)
>   {
> -	int len = fmt->user_len ?: fmt->len;
> +	int len = max(fmt->user_len ?: fmt->len, (int)strlen(fmt->name));
>   
>   	if (symbol_conf.field_sep) {
>   		return __hpp__fmt(hpp, he, get_field, fmtstr, 1,
>
> base-commit: 09a0fa92e5b45e99cf435b2fbf5ebcf889cf8780

This seems to right align the field correctly with a long name. Although 
it's worth noting I had to add a long name to make it obvious.

Reviewed-by: James Clark <james.clark@xxxxxxxxxx>

I saw some other existing issue with small column-width arguments which 
is changed slightly by this patch. But I don't think it's worse:


$ perf report --fields 
overhead,overhead_sys,overhead_us,overhead_guest_us,dso 
--column-widths=3,3,3,3,3

After:
------
Overhead       sys       usr  guest usr long name  Shared Object
  63.78%     0.00%    63.78%                0.00%  ld-linux-x86-64.so

After, width=3:
--------------
Overhead       sys       usr  guest usr long name  Sha
  63.78%   0.00%     63.78%                 0.00%  ld-

Before:
---------------
Overhead       sys       usr  guest usr long name  Shared Object
  63.78%     0.00%    63.78%      0.00%            ld-linux-x86-64.so

Before, width=3:
---------------
Overhead       sys       usr  guest usr long name  Sha
 63.78%    0.00%     63.78%    0.00%               ld-