[PATCH v3 0/4] perf tools: Add progress diagnostics and a false-sharing workload

[Arnaldo Carvalho de Melo <acme@kernel.org>]

Hi,

This series adds progress and stuck-process diagnostics to perf, and a
workload that makes false sharing visible to data type profiling.

The changes are:

  - move perf_config__set_variable() to util/config.c and serialize config
    parser and read-modify-write state, so non-builtin perf code can persist
    configuration changes safely;

  - add 'perf report --progress' for stdio users, showing the current phase,
    percentage, and counts while a session is processed;

  - add the prototype tools/perf/scripts/perf-stuck.sh helper, which samples
    a running perf process and can invoke the accompanying GDB commands when
    progress stops;

  - add 'perf test -w false_sharing', a synthetic TCP-shaped workload with
    identity and packet counters sharing a cacheline, and include it in the
    data type profiling shell test.

The progress backend handles nested phases and completes them on error paths
as well as successful paths. The false-sharing workload uses a shared
volatile instance so the data type profiler can resolve direct accesses to
the individual members.

The perf-stuck helper is intentionally a prototype and requires the usual
/proc access; its optional GDB mode additionally requires gdb and suitable
debug information. When only one CPU is available, the false-sharing
workload warns that it cannot produce cross-CPU traffic but still runs.

Testing:

  make -C tools/perf -j4
  tools/perf/perf test -w false_sharing
  taskset -c 0 tools/perf/perf test -w false_sharing
  bash -n tools/perf/scripts/perf-stuck.sh
  bash -n tools/perf/tests/shell/data_type_profiling.sh
  git diff --check 0ae6fc78c5ce0dfd..485532296710225862daf8ffb19802ae327efe2a

Best regards,

- Arnaldo

What changed from v2:

  - tools/perf/util/config.c: perf_etc_perfconfig() returned NULL when the
    allocation in system_path() fails, and none of its callers check for
    that.  Reported by Sashiko while reviewing v2: the deref reached from
    this series was fixed, and since the same unchecked deref is already
    reachable from the three callers predating it, perf_config_from_file()
    and 'perf daemon' among them, the opportunity was taken to make the
    accessor total as well, falling back to the unresolved path, which for
    the usual absolute ETC_PERFCONFIG is the same string;

  - tools/perf/scripts/perf-stuck.gdb: don't dereference map_symbol.sym
    without checking it for NULL, printing "(no symbol)" instead.  Reported
    by Sashiko while reviewing v2;

  - tools/perf/scripts/perf-stuck.gdb: note next to the structure walks
    that a REFCNT_CHECKING build wraps some structs in a proxy holding the
    original, where this has to read map->orig->dso->orig->name;

  - tools/perf/scripts/perf-stuck.sh: count the samples showing no progress
    when there is no progress to look at, as an empty or missing progress
    log reset the counter on every sample and never fired -g;

  - tools/perf/scripts/perf-stuck.sh: use `--` for pgrep and tail, as a
    process name starting with a hyphen was taken as an option and had the
    script attach to an unrelated process, gdb included when -g is used;

  - tools/perf/scripts/perf-stuck.sh: bound the gdb run with
    `timeout --signal=INT 30`, as the script makes inferior calls and one
    into a perf wedged in a loop never returns, while SIGINT lets gdb
    release the inferior instead of leaving perf stopped.

What changed from v1:

  - avoid calling CPU_SET() with -1 when false_sharing runs with only one
    CPU available in its affinity mask.

   tools/perf/Documentation/perf-report.txt      |  13 +
  tools/perf/builtin-config.c                   |  70 +----
  tools/perf/builtin-report.c                   |  10 +
  tools/perf/scripts/perf-stuck.gdb             | 109 ++++++++
  tools/perf/scripts/perf-stuck.sh              | 184 ++++++++++++++
  tools/perf/tests/builtin-test.c               |   1 +
  tools/perf/tests/shell/data_type_profiling.sh |   9 +-
  tools/perf/tests/tests.h                      |   1 +
  tools/perf/tests/workloads/Build              |   2 +
  tools/perf/tests/workloads/false_sharing.c    | 240 ++++++++++++++++++
  tools/perf/ui/Build                           |   1 +
  tools/perf/ui/progress.h                      |   2 +
  tools/perf/ui/stdio/progress.c                | 162 ++++++++++++
  tools/perf/util/config.c                      | 131 +++++++++-
  tools/perf/util/config.h                      |   2 +
  tools/perf/util/ordered-events.c              |  16 +-
  tools/perf/util/session.c                     |  12 +-
  17 files changed, 882 insertions(+), 83 deletions(-)
  create mode 100644 tools/perf/scripts/perf-stuck.gdb
  create mode 100755 tools/perf/scripts/perf-stuck.sh
  create mode 100644 tools/perf/tests/workloads/false_sharing.c
  create mode 100644 tools/perf/ui/stdio/progress.c

base-commit: 0ae6fc78c5ce0dfd
v1-head: 45d7917f7e05e8a29828ed5f0bbdc94fc938f79f
v2-head: d4f84e4de8890194924ccd897a8e6773e7d4240b
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