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From: Arnaldo Carvalho de Melo <acme@kernel.org>
To: Jiri Olsa <jolsa@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
	lkml <linux-kernel@vger.kernel.org>,
	Ingo Molnar <mingo@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Namhyung Kim <namhyung@kernel.org>,
	Alexander Shishkin <alexander.shishkin@linux.intel.com>,
	Michael Petlan <mpetlan@redhat.com>,
	Ian Rogers <irogers@google.com>,
	linux-perf-users@vger.kernel.org,
	"Frank Ch. Eigler" <fche@redhat.com>
Subject: Re: [RFC] perf record: Disable debuginfod by default
Date: Fri, 10 Dec 2021 10:33:48 -0300	[thread overview]
Message-ID: <YbNXPDVhplHIgayp@kernel.org> (raw)
In-Reply-To: <YbNHCLi/OdMUfgI0@krava>

Em Fri, Dec 10, 2021 at 01:24:40PM +0100, Jiri Olsa escreveu:
> On Fri, Dec 10, 2021 at 09:04:25AM +0100, Peter Zijlstra wrote:
> > On Thu, Dec 09, 2021 at 09:04:25PM +0100, Jiri Olsa wrote:
> > > Adding single perf_debuginfod_setup function and using
> > > it also in perf buildid-cache command.

> > I'm still running with --no-buildid --no-buildid-cache or something like
> > that by default. As long as that remains working I'm good.

> you're good ;-) that will bypass the problem completely

And these days buildids come in PERF_RECORD_MMAP records when possible
(kernel new enough), so no extra step at the end for traversing
PERF_RECORD_MMAP records, read the DSO, find the build id, etc:

$ git log --pretty=fuller -1 --author=jolsa kernel/events/
commit 88a16a1309333e43d328621ece3e9fa37027e8eb
Author:     Jiri Olsa <jolsa@kernel.org>
AuthorDate: Thu Jan 14 14:40:44 2021 +0100
Commit:     Alexei Starovoitov <ast@kernel.org>
CommitDate: Thu Jan 14 19:29:58 2021 -0800

    perf: Add build id data in mmap2 event

    Adding support to carry build id data in mmap2 event.

    The build id data replaces maj/min/ino/ino_generation
    fields, which are also used to identify map's binary,
    so it's ok to replace them with build id data:

      union {
              struct {
                      u32       maj;
                      u32       min;
                      u64       ino;
                      u64       ino_generation;
              };
              struct {
                      u8        build_id_size;
                      u8        __reserved_1;
                      u16       __reserved_2;
                      u8        build_id[20];
              };
      };

    Replaced maj/min/ino/ino_generation fields give us size
    of 24 bytes. We use 20 bytes for build id data, 1 byte
    for size and rest is unused.

    There's new misc bit for mmap2 to signal there's build
    id data in it:

      #define PERF_RECORD_MISC_MMAP_BUILD_ID   (1 << 14)

    Signed-off-by: Jiri Olsa <jolsa@kernel.org>
    Signed-off-by: Alexei Starovoitov <ast@kernel.org>
    Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
    Link: https://lore.kernel.org/bpf/20210114134044.1418404-4-jolsa@kernel.org
$

- Arnaldo

  reply	other threads:[~2021-12-10 13:33 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-12-09 20:04 [RFC] perf record: Disable debuginfod by default Jiri Olsa
2021-12-09 23:39 ` Namhyung Kim
2021-12-10 12:23   ` Jiri Olsa
2021-12-10 16:50     ` Frank Ch. Eigler
2021-12-19 13:04       ` Jiri Olsa
2021-12-10 18:41     ` Namhyung Kim
2021-12-11 19:57       ` Jiri Olsa
2021-12-10  8:04 ` Peter Zijlstra
2021-12-10 12:24   ` Jiri Olsa
2021-12-10 13:33     ` Arnaldo Carvalho de Melo [this message]
2021-12-19 13:06 ` Jiri Olsa
2022-01-15 20:22   ` Arnaldo Carvalho de Melo

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