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

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Message-ID: <CAP-5=fVrFzxcLZG8DyYh2rbd3u4133V6hhrQFCHsq_QMVVW=9g@mail.gmail.com>
Date: Tue, 4 Feb 2025 07:59:01 -0800
From: Ian Rogers <irogers@...gle.com>
To: Namhyung Kim <namhyung@...nel.org>
Cc: Arnaldo Carvalho de Melo <acme@...nel.org>, Kan Liang <kan.liang@...ux.intel.com>, 
	Jiri Olsa <jolsa@...nel.org>, Adrian Hunter <adrian.hunter@...el.com>, 
	Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...nel.org>, 
	LKML <linux-kernel@...r.kernel.org>, linux-perf-users@...r.kernel.org, 
	Howard Chu <howardchu95@...il.com>
Subject: Re: [PATCH v2 1/4] perf trace: Allocate syscall stats only if summary
 is on

On Mon, Feb 3, 2025 at 6:59 PM Namhyung Kim <namhyung@...nel.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@...nel.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:
```
@@ -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.

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

Thanks,
Ian