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

[James Clark]

On 08/01/2025 5:26 pm, James Clark wrote:
> 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:

Ah maybe I was looking at it wrong, before and after are the same with 
width=3, apart from the intended fix. False alarm.

> $ 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-