Re: [PATCH V5 0/6] tools/perf: Add powerpc HTM auxtrace support

[Athira Rajeev <atrajeev@linux.ibm.com>]

> On 7 Aug 2026, at 8:11 PM, Athira Rajeev <atrajeev@linux.ibm.com> wrote:
> 
> Overview:
> This series adds perf tool support for capturing and processing Hardware
> Trace Macro (HTM) trace data on POWER systems.  HTM exposes raw bus-trace
> data via the H_HTM hypervisor call.  The kernel-side HTM PMU driver
> (submitted separately) streams this data into perf AUX buffers and emits
> memory configuration as PERF_SAMPLE_RAW records.
> 
> This series wires up the record and report sides in the perf tool so that
> 'perf record' collects HTM data and 'perf report' writes the trace and
> memory configuration to files ready for post-processing with htmdecode.
> 

Hi All,

I am currently working on addressing Sashiko's review comments for V5 of the patch series.
Before I proceed with posting V6, requesting for any feedback or suggestions that I should incorporate in V6, apart from Sashiko's comments.

Thanks
Athira

> Patch overview:
> Patch 1 refactors the existing powerpc auxtrace dispatch.  All VPA-DTL
> recording logic is moved from arch/powerpc/util/auxtrace.c into its own
> file, arch/powerpc/util/vpa-dtl.c, leaving auxtrace_record__init() as a
> thin per-PMU dispatcher.  This is a prerequisite for adding the HTM
> recording path cleanly.
> 
> Patch 2 adds the HTM recording path (arch/powerpc/util/htm.c and
> util/powerpc-htm.h).  htm_recording_init() sets up the auxtrace_record
> callbacks.  htm_info_fill() stores the PMU type and a (cpu, attr.config)
> pair for each htm evsel into the PERF_RECORD_AUXTRACE_INFO priv[] area.
> The decode side reads these back to map each AUX buffer to its
> (node, chip, core) target using event->auxtrace.cpu.  PERF_SAMPLE_RAW is
> also enabled here so that memory configuration records are captured
> alongside the AUX stream.
> 
> Patch 3 adds a generic weak arch_perf_record__need_read() hook in
> builtin-record.c.  When the hook returns non-zero, perf record performs
> an extra mmap-read pass before disabling events.  The drain loop runs
> until the hook returns 0 or no forward progress is made, then the events
> are disabled and closed normally.
> 
> Patch 4 implements arch_perf_record__need_read() for powerpc.  It reads
> event->count for all open htm evsels via perf_evsel__read() and
> accumulates the values.  The kernel driver sets this count to the number
> of 128-byte HTM trace records written on a successful dump, 1 when the
> AUX buffer is temporarily full but the hypervisor stream is intact, and
> 0 once the stream is exhausted or a hard error occurs.  A non-zero total
> causes the recording loop to perform another read pass.
> 
> Patch 5 adds PERF_AUXTRACE_POWERPC_HTM to the auxtrace_type enum and
> wires the dispatch in perf_event__process_auxtrace_info().  It also
> amends htm_info_fill() to set auxtrace_info->type now that the constant
> is available.
> 
> Patch 6 adds the full HTM decode path in util/powerpc-htm.c.
> powerpc_htm_process_auxtrace_info() reads the (cpu, config) pairs from
> priv[] and builds a cpu_configs[] lookup table.  As each
> PERF_RECORD_AUXTRACE event arrives, process_auxtrace_event() maps it to
> the correct target and writes the data to htm.bin.nX.pX.cX.tX immediately.
> PERF_RECORD_SAMPLE RAW records are written to translation.nX.pX.cX.tX by
> process_event().  Per-run first-write tracking (htm_target_seen) ensures
> O_TRUNC on the first write and O_APPEND on subsequent writes.
> 
> Patches not included in V2:
> Three patches present in V1 are intentionally dropped from this series
> and will be submitted as a follow-on once the core infrastructure gets
> integrated:
> 
>  - htmdecode integration: V1 patch 6 invoked the external htmdecode
>    tool via fork/exec after writing htm.bin.* to decode the raw
>    bus-trace data in-process.  This is deferred because the interface
>    between perf and an external decode tool needs more discussion.
> 
>  - Physical-to-logical address mapping: V1 patch 7 read the current
>    partition ID from /proc/powerpc/lparcfg, parsed the translation.*
>    memory map entries, and mapped physical addresses in the decoded
>    trace to logical addresses within the LPAR.
> 
>  - Synthetic sample generation: V1 patches 8 and 9 created a
>    PERF_TYPE_SYNTH event named "htm", injected synthetic perf samples
>    with the translated logical addresses as sample IP, and wrote a
>    separate .out.l file with logical addresses alongside the decoded
>    trace.  The appropriate abstraction for synthetic HTM samples in the
>    perf tool requires further discussion.
> 
> Usage example:
> Collect HTM trace data from a single chip target:
> 
>  # perf record -C 9 -m,256 \
>      -e htm/nodalchipindex=2,nodeindex=0,htm_type=1/ sleep 3
>  [ perf record: Woken up 1 times to write data ]
>  [ perf record: Captured and wrote 256.277 MB perf.data ]
> 
>  # perf report
> 
> Output files written by perf report:
> 
>  htm.bin.n0.p2.c0.t1       raw HTM bus-trace data
>  translation.n0.p2.c0.t1   memory configuration records
> 
> Multiple targets can be collected simultaneously:
> 
>  # perf record -m,256 \
>      -e htm/nodalchipindex=2,nodeindex=0,htm_type=1,cpu=8/ \
>      -e htm/nodalchipindex=1,nodeindex=0,htm_type=1,cpu=9/ \
>      -a sleep 10
> 
> Testing:
> Tested on POWER11.  Both htm.bin.* and translation.* files are produced
> correctly for single and dual target collection.
> 
> Note: Link to kernel patches:
> https://lore.kernel.org/linuxppc-dev/20260807143734.1224-1-atrajeev@linux.ibm.com/T/#t
> 
> Athira Rajeev (6):
>  tools/perf: Move powerpc VPA-DTL auxtrace init into a separate file
>  tools/perf: Add AUXTRACE recording support for powerpc HTM
>  tools/perf: Add arch hook to drain remaining data before event close
>  tools/perf: Add powerpc callback support for
>    arch_perf_record__need_read
>  tools/perf: Add powerpc HTM auxtrace event processing support
>  tools/perf: Add perf tool support for processing powerpc HTM AUXTRACE
>    records
> 
> tools/perf/arch/powerpc/util/Build      |   2 +
> tools/perf/arch/powerpc/util/auxtrace.c |  98 ++----
> tools/perf/arch/powerpc/util/evsel.c    |  77 ++++
> tools/perf/arch/powerpc/util/htm.c      | 185 ++++++++++
> tools/perf/arch/powerpc/util/vpa-dtl.c  |  96 +++++
> tools/perf/builtin-record.c             |  65 ++++
> tools/perf/util/Build                   |   1 +
> tools/perf/util/auxtrace.c              |   4 +
> tools/perf/util/auxtrace.h              |   1 +
> tools/perf/util/powerpc-htm.c           | 447 ++++++++++++++++++++++++
> tools/perf/util/powerpc-htm.h           |  43 +++
> tools/perf/util/powerpc-vpadtl.h        |   3 +
> tools/perf/util/record.h                |   4 +
> 13 files changed, 954 insertions(+), 72 deletions(-)
> create mode 100644 tools/perf/arch/powerpc/util/htm.c
> create mode 100644 tools/perf/arch/powerpc/util/vpa-dtl.c
> create mode 100644 tools/perf/util/powerpc-htm.c
> create mode 100644 tools/perf/util/powerpc-htm.h
> 
> -- 
> 2.53.0
>