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SubjectRe: [PATCH 2/2] perf record: Add --dry-run option to check cmdline options
Em Thu, Jun 16, 2016 at 08:02:41AM +0000, Wang Nan escreveu:
> With '--dry-run', 'perf record' doesn't do reall recording. Combine with
> llvm.dump-obj option, --dry-run can be used to help compile BPF objects for
> embedded platform.

So these are nice and have value, but can we have a subcommand to do all
this with an expressive name, Something like:

perf bpfcc foo.c -o foo

or shorter:

perf bcc foo.c -o foo

Just like one would use gcc or some other compiler to generate something
for later use?

That if called as:

perf bcc foo.c

Would default to generating a foo.o file.

Then, later, one could use this as a event name, i.e.

trace --event foo

Would, knowing that there is no event named "foo", look at the current
directory (and in some other places perhaps) for a file named "foo" that
was a bpf object file to use as it would a foo.c, shortcircuiting the
bpf compilation code.

If this was done instead:

trace --event foo.c

And foo.c wasn't present, it would fallback to the behaviour described
in the previous paragraph: look for a foo.o or foo bpf object file, etc.

What do you think?

- Arnaldo

> Signed-off-by: Wang Nan <wangnan0@huawei.com>
> Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
> Cc: Alexei Starovoitov <ast@kernel.org>
> Cc: Jiri Olsa <jolsa@kernel.org>
> ---
> tools/perf/Documentation/perf-record.txt | 7 +++++++
> tools/perf/builtin-record.c | 7 +++++++
> 2 files changed, 14 insertions(+)
>
> diff --git a/tools/perf/Documentation/perf-record.txt b/tools/perf/Documentation/perf-record.txt
> index 8dbee83..5b46b1d 100644
> --- a/tools/perf/Documentation/perf-record.txt
> +++ b/tools/perf/Documentation/perf-record.txt
> @@ -360,6 +360,13 @@ particular perf.data snapshot should be kept or not.
>
> Implies --timestamp-filename, --no-buildid and --no-buildid-cache.
>
> +--dry-run::
> +Parse options then exit. --dry-run can be used to detect errors in cmdline
> +options.
> +
> +'perf record --dry-run -e' can act as a BPF script compiler if llvm.dump-obj
> +in config file is set to true.
> +
> SEE ALSO
> --------
> linkperf:perf-stat[1], linkperf:perf-list[1]
> diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
> index d4cf1b0..b1304eb 100644
> --- a/tools/perf/builtin-record.c
> +++ b/tools/perf/builtin-record.c
> @@ -1274,6 +1274,8 @@ static struct record record = {
> const char record_callchain_help[] = CALLCHAIN_RECORD_HELP
> "\n\t\t\t\tDefault: fp";
>
> +static bool dry_run;
> +
> /*
> * XXX Will stay a global variable till we fix builtin-script.c to stop messing
> * with it and switch to use the library functions in perf_evlist that came
> @@ -1393,6 +1395,8 @@ struct option __record_options[] = {
> "append timestamp to output filename"),
> OPT_BOOLEAN(0, "switch-output", &record.switch_output,
> "Switch output when receive SIGUSR2"),
> + OPT_BOOLEAN(0, "dry-run", &dry_run,
> + "Parse options then exit"),
> OPT_END()
> };
>
> @@ -1462,6 +1466,9 @@ int cmd_record(int argc, const char **argv, const char *prefix __maybe_unused)
> if (err)
> return err;
>
> + if (dry_run)
> + return 0;
> +
> err = bpf__setup_stdout(rec->evlist);
> if (err) {
> bpf__strerror_setup_stdout(rec->evlist, err, errbuf, sizeof(errbuf));
> --
> 1.8.3.4

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