[PATCH v2 00/16] perf sysinfo: Add subcommand to probe and summarize PMU capabilities

[Ian Rogers <irogers@google.com>]

This series adds the 'perf sysinfo' subcommand to probe and summarize
the PMU capabilities of a system, or of the system a perf.data file was
recorded on.

It depends on, and applies on top of, the series "perf: Per-env PMUs,
metric event sharing, and recorded event metrics":
https://lore.kernel.org/all/20261113195335.2865725-1-irogers@google.com/
Together they were sent as the single 41 patch v1 series "perf: Per-env
PMUs, recorded event metrics, and perf sysinfo":
https://lore.kernel.org/all/20261103234502.1008382-1-irogers@google.com/
which followed on from the v2 RFC series ("perf sysinfo: Add subcommand
to probe and summarize PMU capabilities"):
https://lore.kernel.org/linux-perf-users/20261017185442.2137623-1-irogers@google.com/

Determining what performance monitoring hardware, driver capabilities,
and event/metric support are available on a system currently requires
piecing together sysfs files under /sys/bus/event_source/devices/,
perf list output, and trial-and-error perf_event_open() calls. Across
architectures and SoCs, support varies widely: an advanced system
provides core PMUs with zero-skid precise event sampling
(PEBS/IBS/SPE), hardware branch stack recording (LBR/BRBE),
user-space counter reading (rdpmc), memory profiling (DATA_SRC),
hardware AUX trace PMUs, memory and PCIe/IO interconnect bandwidth
PMUs, and multi-level pipeline metric drill-down hierarchies, whereas
a minimal system may only offer software timer sampling.

   - Patch 1 exports perf_pmus__scan_skip_duplicates() and adds
     perf_pmu__num_duplicates() to count numbered uncore PMU instances.
   - Patch 2 exports perf_pmu__mem_events_init_pmu() and
     perf_pmu__mem_events_name() for per-PMU memory profiling events.
   - Patches 3-13 add struct perf_pmu::probed and perf_pmu__probe(),
     split into individual capability probes:
     - Patch 3: Basic event opening, counting, interrupt sampling, and
       branch stack sampling (PERF_SAMPLE_BRANCH_STACK).
     - Patch 4: Supported perf_event_sample_format flags (sample_type).
     - Patch 5: Supported precise_ip levels (:p, :pp, :ppp).
     - Patch 6: Privilege and execution-mode exclusion modifiers
       (exclude_user, exclude_kernel, exclude_hv, exclude_idle,
       exclude_host, exclude_guest).
     - Patch 7: Execution and AUX area features (leader_sampling,
       sw_grouping, auto-counter reload, aux_output, aux_pause,
       aux_sample, inherit, sample_freq, write_backward, callchain,
       data_src, weight, pinned, exclusive, format_lost, cgroup).
     - Patch 8: Event group size limits (max events counted
       simultaneously without multiplexing, for both all core counters
       and general-purpose counters only). The number of events accepted
       by perf_event_open() isn't reported as PMUs may accept groups that
       can never be scheduled.
     - Patch 9: User and interrupt sample register bitmasks
       (general-purpose and SIMD vector/predicate registers).
     - Patch 10: Interrupt registers that can only be sampled with
       precise sampling, such as x86 XMM registers captured by PEBS.
     - Patch 11: Memory profiling events (ldlat-loads, ldlat-stores,
       load-store) and supported memory sample formats.
     - Patch 12: User-space perf_event_mmap_page capabilities
       (cap_user_rdpmc, cap_user_time*, pmc_width, and live rdpmc
       verification).
     - Patch 13: Empirically measured branch instruction skid across
       precise_ip levels 0..3 using a noinline nop-runway loop.
   - Patch 14 adds the 'perf sysinfo' subcommand. By default,
     'perf sysinfo' outputs a colorized system capability summary,
     pipeline metric drill-down hierarchy (via <metric>_group chains),
     overall system rating (Advanced, Standard, Basic, Minimal), and any
     missing baseline features. Passing '-p'/'--pmus' (or a PMU glob
     filter, '-v'/'--verbose', '-a'/'--all', or '-j'/'--json') displays
     detailed per-PMU static and probed attributes.
   - Patch 15 adds the 'perf-sysinfo' man page documentation.
   - Patch 16 adds the 'perf sysinfo' shell test.

Changes since v1
================
- Split from the v1 series into this series, which depends on the
  "perf: Per-env PMUs, metric event sharing, and recorded event
  metrics" series.
- Patch 1's perf_pmu__num_duplicates() reports a duplicate count of 1
  for core PMUs, as core PMUs are no longer skipped as duplicates.
- Rebased onto the latest perf-tools-next.
- Addressed Sashiko review feedback:
  - Probing: skip ftrace tracepoints and limit tracepoint candidates,
    don't try an all zero config for tracepoint, breakpoint, kprobe and
    uprobe PMUs, report tracefs errors, treat precise_ip as ignored by
    sampling-only PMUs where all levels open (AMD IBS), probe inherit
    with a task event, probe sample_freq with a low frequency, add
    perf_reg_probe_candidates() for architecture specific extended
    register candidates (x86 eGPRs/SSP and XMM), require rdpmc counts
    to advance and read kernel/perf_user_access for core PMUs.
  - 'perf sysinfo -j' IntrRegisters excludes precise only registers,
    matching the text output.
  - Only check register names in the sysinfo test on x86_64 and
    aarch64.

Changes since v2 RFC
====================
- Split the two perf_pmu__probe() commits into 10 per-capability commits
  (Patches 3-13) and moved the 'perf sysinfo' commits to the end of the
  series (Patches 14-16).
- The per-perf_env PMU support used by 'perf sysinfo -i' is in the
  series this one depends on.

Example outputs
===============

Example default 'perf sysinfo' output on an Intel AlderLake hybrid system:

  $ perf sysinfo
  Summary:
    Core PMUs (2, hybrid): cpu_atom, cpu_core
    Core features:
      Interrupt-based sampling: supported
      Precise event sampling: supported (max_precise: 3 [3 - SAMPLE_IP must have 0 skid, or uses randomization])
      Branch stack sampling (LBR/BRBE): supported (depth: 32 branches)
      User-space counter reading (rdpmc): supported
      Leader sampling: supported
      Memory profiling events (DATA_SRC): supported
      Hardware AUX trace PMUs: intel_bts, intel_pt
    Bus & uncore monitoring:
      Memory bandwidth PMUs: uncore_imc, uncore_imc_free_running
      PCIe / IO interconnect bandwidth PMUs: uncore_arb
    Events & metrics:
      Available events: 3161 total (120 sysfs, 3041 json) across 28 PMUs
      Available metrics: 438 metrics in 192 groups (advanced)
      Metric drill-down levels (6): L1 (TopdownL1: 7 metrics), L2 (TopdownL2: 14 metrics), L3 (TopdownL3: 44 metrics), L4 (TopdownL4: 45 metrics), L5 (TopdownL5: 15 metrics), L6 (TopdownL6: 9 metrics)
    System rating: Advanced (core PMU with precise sampling, branch stack (LBR), user rdpmc, bus PMUs, and metric drill-down)

Example filtered per-PMU output:

  $ perf sysinfo cpu_core
  cpu_core (type: 4 [PERF_TYPE_RAW], core):
    CPUs: 0-15 (16 CPUs)
    Capabilities: branches=32, max_precise=3, pmu_name=alderlake_hybrid
    Formats: event (config:0-7), pc (config:19), edge (config:18), offcore_rsp (config1:0-63), ldlat (config1:0-15), inv (config:23), umask (config:8-15), frontend (config1:0-23), cmask (config:24-31)
    Events: 1563 total (20 sysfs, 1543 json)
    Memory events: ldlat-loads ({cpu_core/mem-loads-aux/,cpu_core/mem-loads,ldlat=30/}:P), ldlat-stores (cpu_core/mem-stores/P)
    Probed capabilities (event: cpu_core/cycles/):
      Modes: counting, sampling, branch_stack
      Precise sampling: :p (1 - SAMPLE_IP must have constant skid), :pp (2 - SAMPLE_IP requested to have 0 skid), :ppp (3 - SAMPLE_IP must have 0 skid, or uses randomization) (max_precise: 3)
      Measured branch skid (instructions from branch):
        level 0 (no :p): min 105, max 174, avg 156.8 (0/32 exact_ip)
        level 1 (:p)   : min 1, max 1, avg 1.0 (0/31 exact_ip)
        level 2 (:pp)  : min 0, max 0, avg 0.0 (31/31 exact_ip)
        level 3 (:ppp) : min 0, max 0, avg 0.0 (32/32 exact_ip)
      Sample types: ip, tid, time, addr, read, callchain, id, cpu, period, stream_id, raw, branch_stack, regs_user, stack_user, weight, data_src, identifier, transaction, regs_intr, aux, cgroup, data_page_size, code_page_size, weight_struct
      User registers: AX, BX, CX, DX, SI, DI, BP, SP, IP, FLAGS, CS, SS, R8, R9, R10, R11, R12, R13, R14, R15
      Intr registers: AX, BX, CX, DX, SI, DI, BP, SP, IP, FLAGS, CS, SS, R8, R9, R10, R11, R12, R13, R14, R15
      Intr registers (precise sampling only): XMM0, XMM1, XMM2, XMM3, XMM4, XMM5, XMM6, XMM7, XMM8, XMM9, XMM10, XMM11, XMM12, XMM13, XMM14, XMM15
      Memory events (probed): ldlat-loads, ldlat-stores (sample types: addr, weight, data_src, transaction, data_page_size, weight_struct)
      Exclusion modifiers: exclude_user, exclude_kernel, exclude_hv, exclude_idle, exclude_host, exclude_guest
      Features: leader_sampling, sw_grouping, inherit, sample_freq, write_backward, callchain, data_src, weight, pinned, exclusive, format_lost, user_rdpmc, user_time, user_time_zero
      User space counter reading (rdpmc): available, enabled, working (width: 48 bits)
      Max event group size: 8
      Max GP event group size: 7

Example output on a Raspberry Pi 5 (ARM Cortex-A76):

  $ sudo perf sysinfo armv8_cortex_a76
  armv8_cortex_a76 (type: 9 [dynamic], core):
    CPUs: 0-3 (4 CPUs)
    Capabilities: slots=0x00000000, threshold_max=0x00000000, bus_slots=0x00000000, bus_width=0x00000000
    Formats: threshold_count (config1:2), event (config:0-15), long (config1:0), rdpmc (config1:1), threshold (config1:5-16), threshold_compare (config1:3-4)
    Events: 1336 total (40 sysfs, 1296 json)
    Probed capabilities (event: armv8_cortex_a76/cycles/):
      Modes: counting, sampling
      Precise sampling: not supported (0 - SAMPLE_IP can have arbitrary skid)
      Measured branch skid (instructions from branch):
        level 0 (no :p): min 340, max 352, avg 346.2 (0/31 exact_ip)
      Sample types: ip, tid, time, addr, read, callchain, id, cpu, period, stream_id, raw, regs_user, stack_user, weight, data_src, identifier, transaction, regs_intr, phys_addr, aux, cgroup, data_page_size, code_page_size, weight_struct
      User registers: x0, x1, x2, x3, x4, x5, x6, x7, x8, x9, x10, x11, x12, x13, x14, x15, x16, x17, x18, x19, x20, x21, x22, x23, x24, x25, x26, x27, x28, x29, lr, sp, pc
      Intr registers: x0, x1, x2, x3, x4, x5, x6, x7, x8, x9, x10, x11, x12, x13, x14, x15, x16, x17, x18, x19, x20, x21, x22, x23, x24, x25, x26, x27, x28, x29, lr, sp, pc
      Exclusion modifiers: exclude_user, exclude_kernel, exclude_hv, exclude_host, exclude_guest
      Features: leader_sampling, sw_grouping, inherit, sample_freq, write_backward, callchain, data_src, weight, pinned, exclusive, format_lost, user_time, user_time_zero, user_time_short
      User space counter reading (rdpmc): available, disabled (sysfs: 0) (width: 32 bits)
      Max event group size: 7
      Max GP event group size: 6

  $ sudo perf sysinfo
  Summary:
    Core PMUs (1): armv8_cortex_a76
    Core features:
      Interrupt-based sampling: supported
      Precise event sampling: missing (0 - SAMPLE_IP can have arbitrary skid)
      Branch stack sampling (LBR/BRBE): missing
      User-space counter reading (rdpmc): missing/disabled
      Leader sampling: supported
      Memory profiling events (DATA_SRC): missing
      Hardware AUX trace PMUs: missing
    Bus & uncore monitoring:
      Memory bandwidth PMUs: missing
      PCIe / IO interconnect bandwidth PMUs: missing
    Events & metrics:
      Available events: 3695 total (2371 sysfs, 1324 json) across 11 PMUs
      Available metrics: 21 metrics in 5 groups (minimal)
      Metric drill-down levels: none (flat metrics only)
    System rating: Basic (core PMU with basic counting/sampling only; missing advanced features)
    Missing baseline features: PCIe/IO interconnect bandwidth PMUs, hardware AUX trace PMU, hardware branch stack sampling (LBR/BRBE), memory bus bandwidth PMUs, memory load/store profiling events, multi-level pipeline drill-down metrics (<metric>_group), precise event sampling (PEBS/IBS/SPE), user-space counter reading (rdpmc)

This patch series was generated with the assistance of antigravity and
Gemini 4.0.

Ian Rogers (16):
  perf pmus: Expose duplicate uncore PMU scanning helpers
  perf mem-events: Expose PMU init and name formatting helpers
  perf pmu: Add perf_pmu__probe() for basic open, counting, and sampling
  perf pmu: Probe supported sample_type flags
  perf pmu: Probe precise_ip levels
  perf pmu: Probe privilege exclusion modifiers
  perf pmu: Probe execution and AUX area features
  perf pmu: Probe event group size limits
  perf pmu: Probe user and interrupt sample register masks
  perf pmu: Probe interrupt registers that require precise sampling
  perf pmu: Probe memory profiling events and sample formats
  perf pmu: Probe user-space mmap capabilities
  perf pmu: Probe branch instruction skid
  perf sysinfo: Add sysinfo subcommand
  perf docs: Add perf-sysinfo man page
  perf test: Add perf sysinfo shell test

 tools/perf/Build                              |    1 +
 tools/perf/Documentation/perf-sysinfo.txt     |  113 +
 tools/perf/Documentation/perf.txt             |    2 +-
 tools/perf/builtin-help.c                     |    3 +-
 tools/perf/builtin-sysinfo.c                  | 2024 ++++++++++++++++
 tools/perf/builtin.h                          |    1 +
 tools/perf/perf.c                             |    1 +
 tools/perf/tests/shell/sysinfo.sh             |   88 +
 tools/perf/util/mem-events.c                  |   12 +-
 tools/perf/util/mem-events.h                  |   20 +
 .../perf/util/perf-regs-arch/perf_regs_x86.c  |   10 +
 tools/perf/util/perf_regs.c                   |   16 +
 tools/perf/util/perf_regs.h                   |    2 +
 tools/perf/util/pmu.c                         | 2145 +++++++++++++++++
 tools/perf/util/pmu.h                         |  197 +-
 tools/perf/util/pmus.c                        |   26 +-
 tools/perf/util/pmus.h                        |   21 +
 17 files changed, 4672 insertions(+), 10 deletions(-)
 create mode 100644 tools/perf/Documentation/perf-sysinfo.txt
 create mode 100644 tools/perf/builtin-sysinfo.c
 create mode 100755 tools/perf/tests/shell/sysinfo.sh


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