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Date: Fri, 25 Apr 2025 11:45:25 -0300
From: Arnaldo Carvalho de Melo <acme@kernel.org>
To: Ian Rogers <irogers@google.com>
Cc: Peter Zijlstra <peterz@infradead.org>, Ingo Molnar <mingo@redhat.com>,
	Namhyung Kim <namhyung@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Alexander Shishkin <alexander.shishkin@linux.intel.com>,
	Jiri Olsa <jolsa@kernel.org>,
	Adrian Hunter <adrian.hunter@intel.com>,
	Kan Liang <kan.liang@linux.intel.com>,
	Athira Rajeev <atrajeev@linux.ibm.com>,
	Kajol Jain <kjain@linux.ibm.com>, Li Huafei <lihuafei1@huawei.com>,
	"Steinar H. Gunderson" <sesse@google.com>,
	Stephen Brennan <stephen.s.brennan@oracle.com>,
	James Clark <james.clark@linaro.org>,
	Andi Kleen <ak@linux.intel.com>, Dmitry Vyukov <dvyukov@google.com>,
	Zhongqiu Han <quic_zhonhan@quicinc.com>,
	Yicong Yang <yangyicong@hisilicon.com>,
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	Krzysztof =?utf-8?Q?=C5=81opatowski?= <krzysztof.m.lopatowski@gmail.com>,
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	Martin =?utf-8?B?TGnFoWth?= <m.liska@foxlink.cz>,
	linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v1 5/5] perf record: Make --buildid-mmap the default
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References: <20250424061943.1321025-1-irogers@google.com>
 <20250424061943.1321025-6-irogers@google.com>
 <CAP-5=fXHay1Qn7c3JUe4nH-cTw8zPhPv6-XWMZdPKpwwT=9n2w@mail.gmail.com>
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On Thu, Apr 24, 2025 at 12:20:44AM -0700, Ian Rogers wrote:
> On Wed, Apr 23, 2025 at 11:19 PM Ian Rogers <irogers@google.com> wrote:
> > @@ -1795,7 +1796,8 @@ record__finish_output(struct record *rec)
> >                         data->dir.files[i].size = lseek(data->dir.files[i].fd, 0, SEEK_CUR);
> >         }
> >
> > -       if (!rec->no_buildid) {
> > +       /* Buildid scanning disabled or build ID in kernel and synthesized map events. */
> > +       if (!rec->no_buildid && !rec->buildid_mmap) {
 
> So I think this is wrong. It matches current behaviors, but it is
> wrong. If we don't process the kernel's mmap events the DSOs won't be
> loaded and the build ID cache won't contain the DSOs. There is also
> the bug that the sample processing to find maps to find DSOs, doesn't
> handle call chains. Given the broken nature of the build ID cache I'm
> not sure it makes any sense for perf record to be by default
> populating it. I think it probably makes sense to consider the default
> population a legacy feature and make -N the default along with
> --buildid-mmap.

The first four patches are good fixes/cleanups, so I'm picking them, ok?

- Arnaldo