[PATCH v1 0/4] Avoid some large stack allocations

From: Ian Rogers
Date: Fri May 26 2023 - 23:43:49 EST

Following on cleaning up .data and .bss in:
Look for some probably too large stack allocations with -Wstack-usage=20000
and pahole.

Don't attempt to cleanup variable length arrays like in:
util/header.c: In function ‘write_cache’:
util/header.c:1269:12: warning: stack usage might be unbounded [-Wstack-usage=]
1269 | static int write_cache(struct feat_fd *ff,
| ^~~~~~~~~~~

Also leave two allocations relating to session/event processing:
util/auxtrace.c: In function ‘auxtrace_queues__add_indexed_event’:
util/auxtrace.c:424:12: warning: stack usage is 65616 bytes [-Wstack-usage=]
424 | static int auxtrace_queues__add_indexed_event(struct auxtrace_queues *queues,
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
util/session.c: In function ‘perf_session__peek_events’:
util/session.c:1822:5: warning: stack usage is 65648 bytes [-Wstack-usage=]
1822 | int perf_session__peek_events(struct perf_session *session, u64 offset,
| ^~~~~~~~~~~~~~~~~~~~~~~~~

The biggest win is for perf inject where 128kb becomes lazily
allocated when aux or guest data is encountered.

Ian Rogers (4):
perf sched: Avoid large stack allocations
perf script: Remove some large stack allocations
perf inject: Lazily allocate event_copy
perf inject: Lazily allocate guest_event event_buf

tools/perf/builtin-inject.c | 31 +++++++++++++++++++++++++------
tools/perf/builtin-sched.c | 26 ++++++++++++++++++++++----
tools/perf/builtin-script.c | 17 +++++++++++++----
3 files changed, 60 insertions(+), 14 deletions(-)