[PATCH v2 0/7] Add io_dir to avoid memory overhead from opendir

[Ian Rogers <irogers@google.com>]

glibc's opendir allocates a minimum of 32kb, when called recursively
for a directory tree the memory consumption can add up - nearly 300kb
during perf start-up when processing modules. Add a stack allocated
variant of readdir sized a little more than 1kb

v2: Remove the feature test and always use a perf supplied getdents64
    to workaround an Alpine Linux issue in v1:
    https://lore.kernel.org/lkml/20231207050433.1426834-1-irogers@google.com/
    As suggested by Krzysztof Łopatowski
    <krzysztof.m.lopatowski@gmail.com> who also pointed to the perf
    trace performance improvements in start-up time eliminating stat
    calls can achieve:
    https://lore.kernel.org/lkml/20250206113314.335376-2-krzysztof.m.lopatowski@gmail.com/
    Convert parse-events and hwmon_pmu to use io_dir.
v1: This was previously part of the memory saving change set:
    https://lore.kernel.org/lkml/20231127220902.1315692-1-irogers@google.com/
    It is separated here and a feature check and syscall workaround
    for missing getdents64 added.

Ian Rogers (7):
  tools lib api: Add io_dir an allocation free readdir alternative
  perf maps: Switch modules tree walk to io_dir__readdir
  perf pmu: Switch to io_dir__readdir
  perf header: Switch mem topology to io_dir__readdir
  perf events: Remove scandir in thread synthesis
  perf parse-events: Switch tracepoints to io_dir__readdir
  perf hwmon_pmu: Switch event discovery to io_dir__readdir

 tools/lib/api/Makefile             |  2 +-
 tools/lib/api/io_dir.h             | 91 ++++++++++++++++++++++++++++++
 tools/perf/util/header.c           | 31 +++++-----
 tools/perf/util/hwmon_pmu.c        | 42 ++++++--------
 tools/perf/util/machine.c          | 19 +++----
 tools/perf/util/parse-events.c     | 32 ++++++-----
 tools/perf/util/pmu.c              | 46 +++++++--------
 tools/perf/util/pmus.c             | 30 ++++------
 tools/perf/util/synthetic-events.c | 22 ++++----
 9 files changed, 194 insertions(+), 121 deletions(-)
 create mode 100644 tools/lib/api/io_dir.h

-- 
2.48.1.502.g6dc24dfdaf-goog