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

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Message-Id: <20230527034324.2597593-1-irogers@google.com>
Date:   Fri, 26 May 2023 20:43:18 -0700
From:   Ian Rogers <irogers@...gle.com>
To:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Ian Rogers <irogers@...gle.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v1 0/4]  Avoid some large stack allocations

Following on cleaning up .data and .bss in:
https://lore.kernel.org/lkml/20230526183401.2326121-1-irogers@google.com/
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(-)

-- 
2.41.0.rc0.172.g3f132b7071-goog