linux-kernel - Re: [PATCH 05/12] perf test: Add 'leafloop' test workload

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Date:   Thu, 17 Nov 2022 10:11:36 -0800
From:   Namhyung Kim <namhyung@...nel.org>
To:     Ian Rogers <irogers@...gle.com>,
        German Gomez <german.gomez@....com>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Jiri Olsa <jolsa@...nel.org>, Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        linux-perf-users@...r.kernel.org, Leo Yan <leo.yan@...aro.org>,
        Zhengjun Xing <zhengjun.xing@...ux.intel.com>,
        James Clark <james.clark@....com>,
        Athira Jajeev <atrajeev@...ux.vnet.ibm.com>
Subject: Re: [PATCH 05/12] perf test: Add 'leafloop' test workload

Hi,

On Thu, Nov 17, 2022 at 9:42 AM Ian Rogers <irogers@...gle.com> wrote:
>
> On Thu, Nov 17, 2022 at 9:24 AM Arnaldo Carvalho de Melo
> <acme@...nel.org> wrote:
> >
> > Em Thu, Nov 17, 2022 at 09:16:58AM -0800, Ian Rogers escreveu:
> > > On Thu, Nov 17, 2022 at 8:15 AM Arnaldo Carvalho de Melo
> > > <acme@...nel.org> wrote:
> > > >
> > > > Em Thu, Nov 17, 2022 at 01:06:16PM -0300, Arnaldo Carvalho de Melo escreveu:
> > > > > Em Wed, Nov 16, 2022 at 03:38:47PM -0800, Namhyung Kim escreveu:
> > > > > > The leafloop workload is to run an infinite loop in the test_leaf
> > > > > > function.  This is needed for the ARM fp callgraph test to verify if it
> > > > > > gets the correct callchains.
> > > > > >
> > > > > >   $ perf test -w leafloop
> > > > >
> > > > > On fedora:36
> > > > >
> > > > > In file included from /usr/include/bits/libc-header-start.h:33,
> > > > >                  from /usr/include/stdlib.h:26,
> > > > >                  from tests/workloads/leafloop.c:2:
> > > > > /usr/include/features.h:412:4: error: #warning _FORTIFY_SOURCE requires compiling with optimization (-O) [-Werror=cpp]
> > > > >   412 | #  warning _FORTIFY_SOURCE requires compiling with optimization (-O)
> > > > >       |    ^~~~~~~
> > > > > cc1: all warnings being treated as errors
> > > > > make[5]: *** [/home/acme/git/perf/tools/build/Makefile.build:96: /tmp/build/perf/tests/workloads/leafloop.o] Error 1
> > > > > make[5]: *** Waiting for unfinished jobs....
> > > > >
> > > > > I'll try removing the _FORTIFY_SOURCE
> > > >
> > > > Works after I added this to datasym.c, leafloop.c and brstack.c:
> > >
> > > Is there a reason we are compiling without -O ? Perhaps we can filter
> >
> > I assumed so as Namhyung added it, perhaps he is just carrying it from
> > the pre-existing shell tests?

Exactly :)

> >
> > I wonder its to have a predictable binary output that the test expects
> > when doing things like hardware tracing? As it come from the coresight
> > tests, IIRC.

I think it just checks frame-pointer based callstacks on ARM to have the
precise results for leaves and their parents.


>
> Would the following in the Build be better:
>
> ```
> # Undefine _FORTIFY_SOURCE as it doesn't work with -O0
> CFLAGS_leafloop.o         = -g -O0 -fno-inline -fno-omit-frame-pointer
> -U_FORTIFY_SOURCE
> ```
>
> We could also use make's `filter-out`. If we are disabling inlining
> then there is also `-fno-optimize-sibling-calls` otherwise we can
> still lose stack frames.

I wonder if it's enough to use -O0 as it's enabled from -O2.
Maybe we can get rid of -fno-inline as well.

German, did you have any concerns for those options?

Thanks,
Namhyung