Re: [PATCH v2 1/4] perf trace: Allocate syscall stats only if summary is on

[Namhyung Kim <namhyung@kernel.org>]

On Tue, Feb 04, 2025 at 07:59:01AM -0800, Ian Rogers wrote:
> On Mon, Feb 3, 2025 at 6:59 PM Namhyung Kim <namhyung@kernel.org> wrote:
> >
> > On Sat, Feb 01, 2025 at 10:57:00PM -0800, Ian Rogers wrote:
> > > On Wed, Jan 29, 2025 at 7:05 PM Namhyung Kim <namhyung@kernel.org> wrote:
> > > >
> > > > The syscall stats are used only when summary is requested.  Let's avoid
> > > > unnecessary operations.  Pass 'trace' pointer to check summary and give
> > > > output file together.
> > >
> > > I don't think this last sentence makes sense.
> >
> > Thanks for your review.  I'd say:  Pass 'trace' pointer instead of doing
> > 'summary' option and 'output' file pointer separately.
> 
> This still doesn't make sense. There is lazier initialization:
> ```
> -               ttrace->syscall_stats = intlist__new(NULL);
> +               if (trace->summary)
> +                       ttrace->syscall_stats = intlist__new(NULL);
> ```
> and there are functions that take a FILE* but now we're going to use
> the one in trace instead:

Yep, those FILE* (fp) was from trace->output.


> ```
> @@ -1568,7 +1569,7 @@ static struct thread_trace *thread__trace(struct
> thread *thread, FILE *fp)
> 
>         return ttrace;
>  fail:
> -       color_fprintf(fp, PERF_COLOR_RED,
> +       color_fprintf(trace->output, PERF_COLOR_RED,
>                       "WARNING: not enough memory, dropping samples!\n");
>         return NULL;
> ```
> So why does the one passed to trace still exist? Unfortunately names
> like "fp" and "output" are not intention revealing.

I think "fp" is a conventional name for file pointers (probably from
K&R?).

> 
> Anyway, from the commit message and the code I don't understand what
> this change is trying to do.

I don't know where you didn't get it.  Apparently my English is not good
enough.  So this commit does two things.

1. check trace->summary before allocating syscall_stats
2. change signature of thread__trace from (thread, fp) to (thread,
   trace) so that it can use trace->output (fp) and trace->summary.

I thought the change #2 is trivial enough to be in the same commit.  But
I can split that if you want.

Thanks,
Namhyung