[PATCHES v3 0/2] perf tools: Add cached probe type detection for evsel

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

Hi,

Checking whether an evsel is a kprobe or uprobe currently requires
walking the PMU list via evsel__find_pmu() on every call.  This is
wasteful when the same evsel is checked repeatedly in hot paths like
trace__fprintf_tp_fields().

Patch 1 adds evsel__is_kprobe(), evsel__is_uprobe(), and
evsel__is_probe() helpers that resolve the probe type on first call
and cache the result in a 3-bit field that fits in existing struct
padding.

Detection covers both PMU-based probes (kprobe/uprobe PMU, detected
by PMU name) and ftrace-based dynamic probes (kprobes/uprobes/fprobes
created via tracefs, which report as PMU "tracepoint").  Ftrace probes
are detected by the __probe_ip field that the kernel adds to all
dynamic probe formats — this is authoritative regardless of the
group/system name the user chose.

Patch 2 is the first user: it guards the __probe_ip field name
comparison in perf trace with evsel__is_probe(), so the strcmp is
skipped entirely for the common case of non-probe tracepoint events.

Patch 3 adds inline stubs for evsel__field() and evsel__common_field()
when libtraceevent is absent.  These were previously declared
unconditionally but defined only inside #ifdef HAVE_LIBTRACEEVENT,
which was harmless until patch 1 added a call from always-compiled
code in evsel.c.

Build-tested with gcc and clang.

Changes in v3:
  - Add patch 3: no-libtraceevent stubs for evsel__field() and
    evsel__common_field().  Without this, NO_LIBTRACEEVENT=1 builds
    fail to link because evsel__resolve_probe_type() calls
    evsel__field() unconditionally (sashiko-bot).

Changes in v2 (patch 1 only):
  - Detect ftrace-based dynamic probes (kprobes/uprobes/fprobes created
    via tracefs) that report PMU "tracepoint" instead of "kprobe"/
    "uprobe".  Check for the __probe_ip field presence in the tracepoint
    format.  Without this, evsel__is_probe() returned false for ftrace
    probes, breaking __probe_ip suppression in perf trace for probes
    created via 'perf probe' (sashiko-bot).
  - Widen probe_type bitfield from 2 to 3 bits for PROBE__FTRACE.

Arnaldo Carvalho de Melo (3):
  perf evsel: Add lazy-initialized probe type detection helpers
  perf trace: Guard __probe_ip suppression with evsel__is_probe()
  perf evsel: Add no-libtraceevent stubs for evsel__field() and evsel__common_field()

 tools/perf/builtin-trace.c |  2 +-
 tools/perf/util/evsel.c    | 53 ++++++++++++++++++++++++++++++++++++++++++++++
 tools/perf/util/evsel.h    | 19 +++++++++++++++++
 3 files changed, 73 insertions(+), 1 deletion(-)

Cc: Aaron Tomlin <atomlin@atomlin.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Namhyung Kim <namhyung@kernel.org>

Developed with AI assistance (Claude/sashiko), tagged in commits.