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Message-ID: <20240322164237.203358-1-ben.gainey@arm.com>
Date: Fri, 22 Mar 2024 16:42:33 +0000
From: Ben Gainey <ben.gainey@....com>
To: peterz@...radead.org,
mingo@...hat.com,
acme@...nel.org,
namhyung@...nel.org
Cc: james.clark@....com,
mark.rutland@....com,
alexander.shishkin@...ux.intel.com,
jolsa@...nel.org,
irogers@...gle.com,
adrian.hunter@...el.com,
linux-perf-users@...r.kernel.org,
linux-kernel@...r.kernel.org,
Ben Gainey <ben.gainey@....com>
Subject: [PATCH v4 0/4] perf: Support PERF_SAMPLE_READ with inherit_stat
This change allows events to use PERF_SAMPLE READ with inherit so long
as both inherit_stat and PERF_SAMPLE_TID are set.
Currently it is not possible to use PERF_SAMPLE_READ with inherit. This
restriction assumes the user is interested in collecting aggregate
statistics as per `perf stat`. It prevents a user from collecting
per-thread samples using counter groups from a multi-threaded or
multi-process application, as with `perf record -e '{....}:S'`. Instead
users must use system-wide mode, or forgo the ability to sample counter
groups. System-wide mode is often problematic as it requires specific
permissions (no CAP_PERFMON / root access), or may lead to capture of
significant amounts of extra data from other processes running on the
system.
Perf already supports the ability to collect per-thread counts with
`inherit` via the `inherit_stat` flag. This patch changes
`perf_event_alloc` relaxing the restriction to combine `inherit` with
`PERF_SAMPLE_READ` so that the combination will be allowed so long as
`inherit_stat` and `PERF_SAMPLE_TID` are enabled.
In this configuration stream ids (such as may appear in the read_format
field of a PERF_RECORD_SAMPLE) are no longer globally unique, rather
the pair of (stream id, tid) uniquely identify each event. Tools that
rely on this, for example to calculate a delta between samples, would
need updating to take this into account. Previously valid event
configurations (system-wide, no-inherit and so on) where each stream id
is the identifier are unaffected.
Changes since v3:
- Cleaned up perf test data changes incorrectly included into this
series from elsewhere.
Changes since v2:
- Rebase on v6.8
- Respond to James Clarke's feedback; fixup some typos and move some
repeated checks into a helper macro.
- Cleaned up checkpatch lints.
- Updated perf test; fixed evsel handling so that existing tests pass
and added new tests to cover the new behaviour.
Changes since v1:
- Rebase on v6.8-rc1
- Fixed value written into sample after child exists.
- Modified handling of switch-out so that context with these events
take the slow path, so that the per-event/per-thread PMU state is
correctly switched.
- Modified perf tools to support this mode of operation.
Ben Gainey (4):
perf: Support PERF_SAMPLE_READ with inherit_stat
tools/perf: Track where perf_sample_ids need per-thread periods
tools/perf: Correctly calculate sample period for inherited
SAMPLE_READ values
tools/perf: Allow inherit + inherit_stat + PERF_SAMPLE_READ when
opening events
include/linux/perf_event.h | 1 +
kernel/events/core.c | 62 ++++++++++----
tools/lib/perf/evlist.c | 1 +
tools/lib/perf/evsel.c | 48 +++++++++++
tools/lib/perf/include/internal/evsel.h | 55 ++++++++++++-
.../test-record-group-sampling-inherit-stat | 62 ++++++++++++++
tools/perf/util/evsel.c | 82 ++++++++++++++++++-
tools/perf/util/evsel.h | 1 +
tools/perf/util/session.c | 11 ++-
9 files changed, 301 insertions(+), 22 deletions(-)
create mode 100644 tools/perf/tests/attr/test-record-group-sampling-inherit-stat
--
2.44.0
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