Message-ID: <8068c8ff-a8ce-4bcd-bb19-2c25b45cf6f3@arm.com>
Date: Fri, 26 Jul 2024 15:38:13 +0100
From: Suzuki K Poulose <suzuki.poulose@....com>
To: Arnaldo Carvalho de Melo <acme@...nel.org>
Cc: James Clark <james.clark@...aro.org>, coresight@...ts.linaro.org,
 gankulkarni@...amperecomputing.com, mike.leach@...aro.org,
 leo.yan@...ux.dev, anshuman.khandual@....com,
 James Clark <james.clark@....com>,
 Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
 Maxime Coquelin <mcoquelin.stm32@...il.com>,
 Alexandre Torgue <alexandre.torgue@...s.st.com>,
 John Garry <john.g.garry@...cle.com>, Will Deacon <will@...nel.org>,
 Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>,
 Namhyung Kim <namhyung@...nel.org>, Mark Rutland <mark.rutland@....com>,
 Jiri Olsa <jolsa@...nel.org>, Ian Rogers <irogers@...gle.com>,
 Adrian Hunter <adrian.hunter@...el.com>,
 "Liang, Kan" <kan.liang@...ux.intel.com>, linux-kernel@...r.kernel.org,
 linux-arm-kernel@...ts.infradead.org,
 linux-stm32@...md-mailman.stormreply.com, linux-perf-users@...r.kernel.org
Subject: Re: [PATCH v6 00/17] coresight: Use per-sink trace ID maps for Perf
 sessions

On 26/07/2024 15:32, Arnaldo Carvalho de Melo wrote:
> On Fri, Jul 26, 2024 at 03:26:04PM +0100, Suzuki K Poulose wrote:
>> Hi Arnaldo
>>
>> On 26/07/2024 15:18, Arnaldo Carvalho de Melo wrote:
>>> On Mon, Jul 22, 2024 at 11:11:42AM +0100, James Clark wrote:
>>>> This will allow sessions with more than CORESIGHT_TRACE_IDS_MAX ETMs
>>>> as long as there are fewer than that many ETMs connected to each sink.
>>>
>>> Hey, may I take the tools part, i.e. patches 0-7 and someone on the ARM
>>> kernel team pick the driver bits?
>>
>> I plan to pick the kernel driver bits for v6.12
> 
> Perhaps it is better for me to wait for that?

Yes, please.

Thanks
Suzuki


> 
> - Arnaldo
>   
>> Kind regards
>> Suzuki
>>
>>>
>>> - Arnaldo
>>>> Each sink owns its own trace ID map, and any Perf session connecting to
>>>> that sink will allocate from it, even if the sink is currently in use by
>>>> other users. This is similar to the existing behavior where the dynamic
>>>> trace IDs are constant as long as there is any concurrent Perf session
>>>> active. It's not completely optimal because slightly more IDs will be
>>>> used than necessary, but the optimal solution involves tracking the PIDs
>>>> of each session and allocating ID maps based on the session owner. This
>>>> is difficult to do with the combination of per-thread and per-cpu modes
>>>> and some scheduling issues. The complexity of this isn't likely to worth
>>>> it because even with multiple users they'd just see a difference in the
>>>> ordering of ID allocations rather than hitting any limits (unless the
>>>> hardware does have too many ETMs connected to one sink).
>>>>
>>>> Per-thread mode works but only until there are any overlapping IDs, at
>>>> which point Perf will error out. Both per-thread mode and sysfs mode are
>>>> left to future changes, but both can be added on top of this initial
>>>> implementation and only sysfs mode requires further driver changes.
>>>>
>>>> The HW_ID version field hasn't been bumped in order to not break Perf
>>>> which already has an error condition for other values of that field.
>>>> Instead a new minor version has been added which signifies that there
>>>> are new fields but the old fields are backwards compatible.
>>>>
>>>> Changes since v5:
>>>>     * Hide queue number printout behind -v option
>>>>     * Style change in cs_etm__process_aux_output_hw_id()
>>>>     * Move new format enum to an earlier commit to reduce churn
>>>>
>>>> Changes since v4:
>>>>
>>>>     * Fix compilation failure when TRACE_ID_DEBUG is set
>>>>     * Expand comment about not freeing individual trace IDs in
>>>>       free_event_data()
>>>>
>>>> Changes since v3:
>>>>
>>>>     * Fix issue where trace IDs were overwritten by possibly invalid ones
>>>>       by Perf in unformatted mode. Now the HW_IDs are also used for
>>>>       unformatted mode unless the kernel didn't emit any.
>>>>     * Add a commit to check the OpenCSD version.
>>>>     * Add a commit to not save invalid IDs in the Perf header.
>>>>     * Replace cs_etm_queue's formatted and formatted_set members with a
>>>>       single enum which is easier to use.
>>>>     * Drop CORESIGHT_TRACE_ID_UNUSED_FLAG as it's no longer needed.
>>>>     * Add a commit to print the queue number in the raw dump.
>>>>     * Don't assert on the number of unformatted decoders if decoders == 0.
>>>>
>>>>
>>>> Changes since v2:
>>>>
>>>>     * Rebase on coresight-next 6.10-rc2 (b9b25c8496).
>>>>     * Fix double free of csdev if device registration fails.
>>>>     * Fix leak of coresight_trace_id_perf_start() if trace ID allocation
>>>>       fails.
>>>>     * Don't resend HW_ID for sink changes in per-thread mode. The existing
>>>>       CPU field on AUX records can be used to track this instead.
>>>>     * Tidy function doc for coresight_trace_id_release_all()
>>>>     * Drop first two commits now that they are in coresight-next
>>>>     * Add a commit to make the trace ID spinlock local to the map
>>>>
>>>> Changes since V1:
>>>>
>>>>    * Rename coresight_device.perf_id_map to perf_sink_id_map.
>>>>    * Instead of outputting a HW_ID for each reachable ETM, output
>>>>      the sink ID and continue to output only the HW_ID once for
>>>>      each mapping.
>>>>    * Keep the first two Perf patches so that it applies cleanly
>>>>      on coresight-next, although they have been applied on perf-tools-next
>>>>    * Add new *_map() functions to the trace ID public API instead of
>>>>      modifying existing ones.
>>>>    * Collapse "coresight: Pass trace ID map into source enable" into
>>>>      "coresight: Use per-sink trace ID maps for Perf sessions" because the
>>>>      first commit relied on the default map being accessible which is no
>>>>      longer necessary due to the previous bullet point.
>>>>
>>>>
>>>> James Clark (17):
>>>>     perf: cs-etm: Create decoders after both AUX and HW_ID search passes
>>>>     perf: cs-etm: Allocate queues for all CPUs
>>>>     perf: cs-etm: Move traceid_list to each queue
>>>>     perf: cs-etm: Create decoders based on the trace ID mappings
>>>>     perf: cs-etm: Only save valid trace IDs into files
>>>>     perf: cs-etm: Support version 0.1 of HW_ID packets
>>>>     perf: cs-etm: Print queue number in raw trace dump
>>>>     perf: cs-etm: Add runtime version check for OpenCSD
>>>>     coresight: Remove unused ETM Perf stubs
>>>>     coresight: Clarify comments around the PID of the sink owner
>>>>     coresight: Move struct coresight_trace_id_map to common header
>>>>     coresight: Expose map arguments in trace ID API
>>>>     coresight: Make CPU id map a property of a trace ID map
>>>>     coresight: Use per-sink trace ID maps for Perf sessions
>>>>     coresight: Remove pending trace ID release mechanism
>>>>     coresight: Emit sink ID in the HW_ID packets
>>>>     coresight: Make trace ID map spinlock local to the map
>>>>
>>>>    drivers/hwtracing/coresight/coresight-core.c  |  37 +-
>>>>    drivers/hwtracing/coresight/coresight-dummy.c |   3 +-
>>>>    .../hwtracing/coresight/coresight-etm-perf.c  |  43 +-
>>>>    .../hwtracing/coresight/coresight-etm-perf.h  |  18 -
>>>>    .../coresight/coresight-etm3x-core.c          |   9 +-
>>>>    .../coresight/coresight-etm4x-core.c          |   9 +-
>>>>    drivers/hwtracing/coresight/coresight-priv.h  |   1 +
>>>>    drivers/hwtracing/coresight/coresight-stm.c   |   3 +-
>>>>    drivers/hwtracing/coresight/coresight-sysfs.c |   3 +-
>>>>    .../hwtracing/coresight/coresight-tmc-etr.c   |   5 +-
>>>>    drivers/hwtracing/coresight/coresight-tmc.h   |   5 +-
>>>>    drivers/hwtracing/coresight/coresight-tpdm.c  |   3 +-
>>>>    .../hwtracing/coresight/coresight-trace-id.c  | 138 ++--
>>>>    .../hwtracing/coresight/coresight-trace-id.h  |  70 +-
>>>>    include/linux/coresight-pmu.h                 |  17 +-
>>>>    include/linux/coresight.h                     |  21 +-
>>>>    tools/build/feature/test-libopencsd.c         |   4 +-
>>>>    tools/include/linux/coresight-pmu.h           |  17 +-
>>>>    tools/perf/Makefile.config                    |   2 +-
>>>>    tools/perf/arch/arm/util/cs-etm.c             |  11 +-
>>>>    .../perf/util/cs-etm-decoder/cs-etm-decoder.c |  49 +-
>>>>    .../perf/util/cs-etm-decoder/cs-etm-decoder.h |   3 +-
>>>>    .../util/cs-etm-decoder/cs-etm-min-version.h  |  13 +
>>>>    tools/perf/util/cs-etm.c                      | 629 +++++++++++-------
>>>>    tools/perf/util/cs-etm.h                      |  12 +-
>>>>    25 files changed, 650 insertions(+), 475 deletions(-)
>>>>    create mode 100644 tools/perf/util/cs-etm-decoder/cs-etm-min-version.h
>>>>
>>>> -- 
>>>> 2.34.1

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