linux-kernel - [PATCH 0/2] perf: Allow closing siblings' file descriptors

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Message-Id: <20200708151635.81239-1-alexander.shishkin@linux.intel.com>
Date:   Wed,  8 Jul 2020 18:16:33 +0300
From:   Alexander Shishkin <alexander.shishkin@...ux.intel.com>
To:     Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Arnaldo Carvalho de Melo <acme@...hat.com>
Cc:     Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
        Jiri Olsa <jolsa@...nel.org>, alexey.budankov@...ux.intel.com,
        adrian.hunter@...el.com,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Subject: [PATCH 0/2] perf: Allow closing siblings' file descriptors

Hi guys,

I've been looking at reducing the number of open file descriptors per perf
session. If we retain one descriptor per event, in a large group they add
up. At the same time, we're not actually using them for anything after the
SET_OUTPUT and maybe SET_FILTER ioctls. So, this series is a stab at that.

So, I added a new flag to the perf_event_open() that tells perf to keep
the event around after its file descriptor gets closed, for as long as its
group leader is alive. Since this is a new behavior, the flag is an opt-in.

I also hacked this into the perf tool (mostly perf record, but I'll hack
stat as well if this general approach is agreeable).

Alexander Shishkin (2):
  perf: Add closing sibling events' file descriptors
  perf record: Support closing siblings' file descriptors

 include/linux/perf_event.h              |   7 ++
 include/uapi/linux/perf_event.h         |   1 +
 kernel/events/core.c                    | 149 +++++++++++++++++-------
 tools/include/uapi/linux/perf_event.h   |   1 +
 tools/lib/perf/evlist.c                 |  30 ++++-
 tools/lib/perf/evsel.c                  |  21 ++++
 tools/lib/perf/include/internal/evsel.h |   4 +
 tools/perf/builtin-record.c             |  48 ++++++--
 tools/perf/util/cpumap.c                |   4 +
 tools/perf/util/evlist.c                |   4 +-
 tools/perf/util/evsel.c                 |  17 ++-
 tools/perf/util/evsel.h                 |   3 +
 12 files changed, 234 insertions(+), 55 deletions(-)

-- 
2.27.0