Re: [PATCH v6 00/17] coresight: Use per-sink trace ID maps for Perf sessions

[Suzuki K Poulose <suzuki.poulose@arm.com>]

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

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