linux-kernel - Re: [RFC 00/48] perf tools: Introduce data type profiling (v1)

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Message-ID: <ZTl0MdKauLd21ahn@tassilo>
Date:   Wed, 25 Oct 2023 13:01:53 -0700
From:   Andi Kleen <ak@...ux.intel.com>
To:     Namhyung Kim <namhyung@...nel.org>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Jiri Olsa <jolsa@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ian Rogers <irogers@...gle.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Ingo Molnar <mingo@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-perf-users@...r.kernel.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Stephane Eranian <eranian@...gle.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        linux-toolchains@...r.kernel.org,
        linux-trace-devel@...r.kernel.org,
        Ben Woodard <woodard@...hat.com>,
        Joe Mario <jmario@...hat.com>,
        Kees Cook <keescook@...omium.org>,
        David Blaikie <blaikie@...gle.com>,
        Xu Liu <xliuprof@...gle.com>,
        Kan Liang <kan.liang@...ux.intel.com>,
        Ravi Bangoria <ravi.bangoria@....com>
Subject: Re: [RFC 00/48] perf tools: Introduce data type profiling (v1)

On Tue, Oct 24, 2023 at 10:51:41PM -0700, Namhyung Kim wrote:
> On Tue, Oct 24, 2023 at 7:09 PM Andi Kleen <ak@...ux.intel.com> wrote:
> >
> > >
> > > >
> > > > The main difference seems to be that mine was more for perf script
> > > > (e.g. i supported PT decoding), while you are more focused on sampling.
> > > > I relied on the kprobes/uprobes engine, which unfortunately was always
> > > > quite slow and had many limitations.
> > >
> > > Right, I think dealing with regular samples would be more useful.
> >
> > My code supported samples too, but only through perf script, not report.
> >
> > See
> >
> > https://git.kernel.org/pub/scm/linux/kernel/git/ak/linux-misc.git/commit/?h=perf/var-resolve-7&id=4775664750a6296acb732b7adfa224c6a06a126f
> >
> > for an example.
> >
> > My take was that i wasn't sure that perf report is the right interface
> > to visualize the variables changing -- to be really usable you probably
> > need some plots and likely something like an UI.
> 
> I see.  Your concern is to see how variables are changing.
> But it seems you only displayed constant values.

Yes the examples were not very good, but that was the intention.
Values can be much more powerful than only types!

For PT I also had special compiler patch that added suitable ptwrites
(see [1]) that allowed to track any variable.

-Andi

[1] https://github.com/andikleen/gcc-old-svn/tree/ptwrite-18