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

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Date:   Mon, 12 Jun 2023 16:01:59 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Ian Rogers <irogers@...gle.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 0/4]  Avoid some large stack allocations

Em Fri, May 26, 2023 at 08:43:18PM -0700, Ian Rogers escreveu:
> 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.

Thanks, applied.

- Arnaldo

 
> 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
> 

-- 

- Arnaldo