Messages in this thread | ![/](/images/icornerl.gif) | | Date | Thu, 19 Jan 2023 12:00:00 +0000 | Subject | Re: [PATCH v7 00/15] coresight: Add new API to allocate trace source ID values | From | Suzuki K Poulose <> |
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Hi Arnaldo,
On 16/01/2023 12:49, Mike Leach wrote: > The current method for allocating trace source ID values to sources is > to use a fixed algorithm for CPU based sources of (cpu_num * 2 + 0x10). > The STM is allocated ID 0x1. > > This fixed algorithm is used in both the CoreSight driver code, and by > perf when writing the trace metadata in the AUXTRACE_INFO record. > > The method needs replacing as currently:- > 1. It is inefficient in using available IDs. > 2. Does not scale to larger systems with many cores and the algorithm > has no limits so will generate invalid trace IDs for cpu number > 44. > > Additionally requirements to allocate additional system IDs on some > systems have been seen. > > This patch set introduces an API that allows the allocation of trace IDs > in a dynamic manner. > > Architecturally reserved IDs are never allocated, and the system is > limited to allocating only valid IDs. > > Each of the current trace sources ETM3.x, ETM4.x and STM is updated to use > the new API. > > For the ETMx.x devices IDs are allocated on certain events > a) When using sysfs, an ID will be allocated on hardware enable, or a read of > sysfs TRCTRACEID register and freed when the sysfs reset is written. > > b) When using perf, ID is allocated on during setup AUX event, and freed on > event free. IDs are communicated using the AUX_OUTPUT_HW_ID packet. > The ID allocator is notified when perf sessions start and stop > so CPU based IDs are kept constant throughout any perf session. > > > Note: This patchset breaks some backward compatibility for perf record and > perf report. > > The version of the AUXTRACE_INFO has been updated to reflect the fact that > the trace source IDs are generated differently. This will > mean older versions of perf report cannot decode the newer file. > > Appies to coresight/next > > Changes since v6: > 1) Export perf_report_aux_output_id() Acked by Peter, > 2) Update to ETMv3 docs requested by suzuki > 3) rebased and re-tested on coresight/next (6.2-rc2) > > Changes since v5: (requested by suzuki) > 1) Prefer odd ID values for system IDs to avoid overlap with legacy CPU IDs > 2) Some style changes > > Changes since v4: > 1) update to ensure that compiling after each individual patch added still > works - ie. git bisect not broken through the patchset.. > > 2) Revision to some of the now redundant code in cs-etm (James) > > 3) Comments and other minor fixes requested by Suzuki. > > Changes since v3: > 1) Fixed aarch32 build error in ETM3.x driver. > Reported-by: kernel test robot <lkp@intel.com> > > Changes since v2: > 1) Improved backward compatibility: (requested by James) > > Using the new version of perf on an old kernel will generate a usable file > legacy metadata values are set by the new perf and will be used if mew > ID packets are not present in the file. > > Using an older version of perf / simpleperf on an updated kernel may still > work. The trace ID allocator has been updated to use the legacy ID values > where possible, so generated file and used trace IDs will match up to the > point where the legacy algorithm is broken anyway. > > 2) Various changes to the ID allocator and ID packet format. > (suggested by Suzuki) > > 3) per CPU ID info in allocator now stored as atomic type to allow a passive read > without taking the allocator spinlock. perf flow now allocates and releases ID > values in setup_aux / free_event. Device enable and event enable use the passive > read to set the allocated values. This simplifies the locking mechanisms on the > perf run and fixes issues that arose with locking dependencies. > > Changes since v1: > (after feedback & discussion with Mathieu & Suzuki). > > 1) API has changed. The global trace ID map is managed internally, so it > is no longer passed in to the API functions. > > 2) perf record does not use sysfs to find the trace IDs. These are now > output as AUX_OUTPUT_HW_ID events. The drivers, perf record, and perf report > have been updated accordingly to generate and handle these events. > > Mike Leach (15): > coresight: trace-id: Add API to dynamically assign Trace ID values > coresight: Remove obsolete Trace ID unniqueness checks > coresight: perf: traceid: Add perf ID allocation and notifiers > coresight: stm: Update STM driver to use Trace ID API > coresight: etm4x: Update ETM4 driver to use Trace ID API > coresight: etm3x: Update ETM3 driver to use Trace ID API > coresight: etmX.X: stm: Remove trace_id() callback > coresight: trace id: Remove legacy get trace ID function. > perf: cs-etm: Move mapping of Trace ID and cpu into helper function > perf: cs-etm: Update record event to use new Trace ID protocol > kernel: events: Export perf_report_aux_output_id() > perf: cs-etm: Handle PERF_RECORD_AUX_OUTPUT_HW_ID packet > coresight: events: PERF_RECORD_AUX_OUTPUT_HW_ID used for Trace ID > coresight: trace-id: Add debug & test macros to Trace ID allocation > coresight: etm3x: docs: Alter sysfs documentation for trace id updates
I have pushed the kernel patches on this series to coresight tree next[0].
I will be sending them out to Greg for v6.3. Please could you queue the perf tool changes in the series ? i.e., Patches 9,10 and 12.
[0] https://git.kernel.org/pub/scm/linux/kernel/git/coresight/linux.git/log/?h=next
Kind regards Suzuki
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